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19-4372; Rev 2; 7/09
KIT ATION EVALU E AILABL AV
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
General Description Features
o o o o o o o o o o o o o o o o o o o Single-/Dual-Phase, Quick-PWM Controllers MAX17021 IMVP-6+ (Montevina) MAX17082/MAX17482 IMVP-6.5 (Calpella) 0.5% VOUT Accuracy Over Line, Load, and Temperature 7-Bit 0 to 1.50V VID Control Dynamic Phase Selection Optimizes Active/Sleep Efficiency Transient Phase Overlap Reduces Output Capacitance Integrated Boost Switches Active Voltage Positioning with Adjustable Gain Programmable 200kHz to 800kHz Switching Frequency Accurate Current Balance and Current Limit Adjustable Slew-Rate Control Power-Good, Clock Enable, and Thermal-Fault Outputs Phase Current Imbalance Fault Output Drives Large Synchronous Rectifier MOSFETs 4V to 26V Battery Input-Voltage Range Undervoltage and Thermal-Fault Protection Overvoltage Protection (MAX17021/MAX17082) Soft-Startup and Soft-Shutdown
MAX17021/MAX17082/MAX17482
The MAX17021/MAX17082/MAX17482 are 2/1-phaseinterleaved Quick-PWMTM step-down VID power-supply controllers for notebook CPUs. True out-of-phase operation reduces input ripple current requirements and output- voltage ripple, while easing component selection and layout difficulties. The Quick-PWM control provides instantaneous response to fast load-current steps. Active voltage positioning reduces power dissipation and bulk output capacitance requirements and allows ideal positioning compensation for tantalum, polymer, or ceramic bulk output capacitors. A slew-rate controller allows controlled transitions between VID codes, controlled soft-start and shutdown, and controlled exit from suspend. A thermistor-based temperature sensor provides a programmable thermal-fault output (VRHOT). A current monitor output (IMON) provides an analog current output proportional to the power consumed by the CPU (MAX17082/MAX17482 only). Output undervoltage, overvoltage (MAX17021/MAX17082 only), and thermal protection shut the controller down when any of these faults are detected. A voltage-regulator power-OK (PWRGD) output indicates the output is in regulation. Additionally, the MAX17021/MAX17082/MAX17482 feature true differential current sense and a phase-good (PHASEGD) output that indicates a phase imbalance fault condition. The MAX17021 supports the IMVP-6+ specification while the MAX17082/MAX17482 support the IMVP-6.5 requirements. The MAX17021/MAX17082/MAX17482 are available in a 5mm x 5mm, 40-pin TQFN package.
Pin Configuration
BST1 BST2 20 PHASEGD 19 PWRGD 18 CLKEN 17 V3P3 16 TON 15 PSI 14 DPRSLPVR *EP 13 SHDN 12 CSP2 11 CSN2 1 PGDIN 2 THRM 3 N.C. (IMON) 4 ILIM 5 TIME 6 VCC 7 CCI 8 FB 9 FBAC 10 GNDS DH1 DH2 DL1 DL2 VDD LX1 LX2
TOP VIEW
IMVP-6+/IMVP-6.5 Core Supply Multiphase CPU Core Supply Voltage-Positioned, Step-Down Converters Notebook/Desktop Computers Blade Servers
DPRSTP (SLOW) 31 D0 32 D1 33 D2 34 D3 35 D4 36
30 29 28 27 26 25 24 23 22 21
Ordering Information
PART MAX17021GTL+ MAX17082GTL+ TEMP RANGE -40C to +105C -40C to +105C PIN-PACKAGE 40 TQFN-EP* 40 TQFN-EP*
D5 37 D6 38 CSP1 39 CSN1 40
MAX17021 (MAX17082) MAX17482
+
MAX17482GTL+ -40C to +105C 40 TQFN-EP* +Denotes a lead-free(Pb)/RoHS-compliant package. *EP = Exposed pad.
THIN QFN
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
() DESIGNATES MAX17082/MAX17482 PIN NAME. *EXPOSED PAD. CONNECTED TO GND.
________________________________________________________________ Maxim Integrated Products
VRHOT
Applications
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ABSOLUTE MAXIMUM RATINGS
VCC, VDD, V3P3 to GND ...........................................-0.3V to +6V D0-D6 to GND..........................................................-0.3V to +6V PGDIN, DPRSLPVR, PSI to GND..............................-0.3V to +6V DPRSTP (MAX17021) to GND ..................................-0.3V to +6V SLOW (MAX17082/MAX17482) to GND...................-0.3V to +6V CSP1, CSP2, CSN1, CSN2 to GND..........................-0.3V to +6V THRM, ILIM, PHASEGD to GND...............................-0.3V to +6V PWRGD, VRHOT to GND .........................................-0.3V to +6V CLKEN to GND ...........................................-0.3V to V3P3 + 0.3V FB, FBAC to GND .........................................-0.3V to VCC + 0.3V TIME, CCI to GND.........................................-0.3V to VCC + 0.3V IMON to GND (MAX17021/MAX17082) ........-0.3V to VCC + 0.3V GNDS to GND .......................................................-0.3V to +0.3V SHDN to GND (Note 1)...........................................-0.3V to +16V TON to GND ...........................................................-0.3V to +30V DL1, DL2 to GND..........................................-0.3V to VDD + 0.3V BST1, BST2 to GND ...............................................-0.3V to +36V BST1, BST2 to VDD .................................................-0.3V to +30V LX1 to BST1..............................................................-6V to +0.3V LX2 to BST2..............................................................-6V to +0.3V DH1 to LX1 ..............................................(-0.3V to VBST1) + 0.3V DH2 to LX2 ..............................................(-0.3V to VBST2) + 0.3V Continuous Power Dissipation 40-Pin 5mm x 5mm TQFN Up to +70C.....................1778mW (derate above +70C) ............................................22.2mW/C Operating Temperature Range .........................-40C to +105C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +165C Lead Temperature (soldering, 10s) .................................+300C
Note 1: SHDN might be forced to 12V for the purpose of debugging prototype boards using the no-fault test mode, which disables fault protection and overlapping operation.
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN1 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER PWM CONTROLLER Input-Voltage Range VCC, VDD V3P3 Measured at FB with respect to GNDS; includes loadregulation error (Note 2) MAX17021 IMVP-6+ MAX17082/MAX17482 IMVP-6.5 VCC = 4.5V to 5.5V, VIN = 4.5V to 26V TA = +25C A GNDS IGNDS VTIME VOUT/ VGNDS TA = +25C RTIME = 71.5k DAC codes from 0.8125V to 1.5000V DAC codes from 0.3750V to 0.8000V DAC codes from 0 to 0.3625V 4.5 3.0 -0.5 -7 -20 1.194 1.094 -0.1 -200 0.97 -0.5 1.985 2.000 1.00 1.200 1.100 0.1 +0.1 +200 1.03 +0.5 2.015 5.5 3.6 +0.5 +7 mV +20 1.206 1.106 V % A mV V/V A V V % SYMBOL CONDITIONS MIN TYP MAX UNITS
DC Output-Voltage Accuracy
VOUT
Boot Voltage Line Regulation Error FB Input Bias Current GNDS Input Range GNDS Gain GNDS Input Bias Current TIME Regulation Voltage
VBOOT
2
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN1 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER SYMBOL RTIME = 71.5k CONDITIONS (12.5mV/s nominal) RTIME = 35.7k (25mV/s nominal) to 178k (5mV/s nominal) Soft-start and soft-shutdown: RTIME = 35.7k (3.125mV/s nominal) to 178k (0.625mV/s nominal) Slow: IMVP-6.5 (MAX17082/MAX17482): VSLOW = 0V, 1/2 of nominal slew rate, RTIME = 71.5k (6.25mV/s nominal); IMVP-6+ (MAX17021): VDPRSTP = VDPRSLPVR = 5V, 1/4 of nominal slew rate, RTIME = 71.5k (3.125mV/s nominal) Slow: IMVP-6.5 (MAX17082/MAX17482): VSLOW = 0V, 1/2 of nominal slew rate, RTIME = 35.7k (12.5mV/s nominal) to 178k (2.5mV/s nominal); IMVP-6+ (MAX17021): VDPRSTP = VDPRSLPVR = 5V 1/4 of nominal slew rate, RTIME = 35.7k (6.25mV/s nominal) to 178k (1.25mV/s nominal) RTON = 96.75k (600kHz per phase), 167ns nominal On-Time t ON Measured at DH_ (Note 3) RTON = 200k (300kHz per phase), 333ns nominal RTON = 303.25k 500ns nominal Minimum Off-Time TON Shutdown Input Current BIAS CURRENTS Quiescent Supply Current (VCC) Quiescent Supply Current (VDD) ICC IDD Measured at VCC, VDPRSLPVR = 5V, FB forced above the regulation point Measured at VDD, VDPRSLPVR = 0V, FB forced above the regulation point, TA = +25C 2.5 0.02 5 1 mA A t OFF(MIN) IRTON,SDN Measured at DH_ (Note 3) SHDN = GND, VIN = 26V, VCC = VDD = 0V or 5V, TA = +25C (200kHz per phase), MIN -10 -15 TYP MAX +10 +15 UNITS
MAX17021/MAX17082/MAX17482
-25
+25
-15
+15 %
TIME Slew-Rate Accuracy
-15
+15
-15 -10 -15 300 0.01
+15 +10 +15 350 0.1 ns A %
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3
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN1 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Quiescent Supply Current (V3P3) Shutdown Supply Current (VCC) Shutdown Supply Current (VDD) Shutdown Supply Current (V3P3) FAULT PROTECTION Skip mode after output reaches the regulation voltage or PWM mode; measured at FB with respect to the voltage target set by the VID code; see Table 4. VOVP Soft-start, soft-shutdown, skip mode, and output have not reached the regulation voltage; measured at FB IMVP-6.5 (MAX17082) IMVP-6+ (MAX17021) SYMBOL I3P3 ICC,SDN IDD,SDN I3P3,SDN CONDITIONS Measured at V3P3, FB forced within the CLKEN power-good window Measured at VCC, SHDN = GND, TA = +25C Measured at VDD, SHDN = GND, TA = +25C Measured at V3P3, SHDN = GND, TA = +25C MIN TYP 2 0.01 0.01 0.01 MAX 4 1 1 1 UNITS A A A A
250
300
350
mV
Output OvervoltageProtection Threshold (MAX17021/MAX17082 Only)
1.45 1.75
1.50 1.80 0.8 10
1.55 1.85 V
Minimum OVP threshold; measured at FB Output OvervoltagePropagation Delay (MAX17021/MAX17082 Only) Output UndervoltageProtection Threshold Output UndervoltagePropagation Delay CLKEN Startup Delay and Boot Time Period PWRGD Startup Delay t OVP FB forced 25mV above trip threshold Measured at FB with respect to the voltage target set by the VID code; see Table 4 FB forced 25mV below trip threshold Measured from the time when FB reaches the boot target voltage (Note 2) Measured at startup from the time when CLKEN goes low Lower threshold, falling edge (undervoltage) Upper threshold, rising edge (overvoltage) 20 3
s
VUVP tUVP tBOOT
-450
-400 10 60 6.5
-350
mV s
100 10
s ms
CLKEN and PWRGD Threshold
Measured at FB with respect to the voltage target set by the VID code; see Table 4, 20mV hysteresis (typ)
-350
-300
-250 mV
+150
+200
+250
CLKEN and PWRGD Delay PHASEGD Delay
FB forced 25mV outside the PWRGD trip thresholds V(CCI,FB) forced 25mV outside trip thresholds
10 10
s s
4
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN1 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER CLKEN, PWRGD, and PHASEGD Transition Blanking Time (VID Transitions) PHASEGD Transition Blanking Time (Phase 2 Enable Transitions) CLKEN Output Low Voltage CLKEN Output High Voltage PWRGD, PHASEGD Output Low Voltage PWRGD, PHASEGD Leakage Current CSN1 Pulldown Resistance in Shutdown VCC Undervoltage Lockout (UVLO) Threshold THERMAL PROTECTION VRHOT Trip Threshold VRHOT Delay VRHOT Output On-Resistance VRHOT Leakage Current THRM Input Leakage Thermal-Shutdown Threshold ITHRM T SHDN t VRHOT Measured at THRM as a percentage of VCC, falling edge, typical hysteresis = 75mV THRM forced 25mV below the VRHOT trip threshold, falling edge 29 30 10 2 10 1 -0.1 160 7 45 20 -4 10 50 22.5 13 55 25 +4 mV mV +0.1 A A C 31 % s VUVLO(VCC) SYMBOL CONDITIONS Measured from the time when FB reaches the target voltage (Note 2) MIN TYP MAX UNITS
MAX17021/MAX17082/MAX17482
tBLANK
20
s
Number of DH2 pulses for which PHASEGD is blanked after phase 2 is enabled Low state, ISINK = 3mA High state, I SOURCE = 3mA Low state, I SINK = 3mA High-impedance state, PWRGD, PHASEGD forced to 5V, TA = +25C SHDN = 0, measured after soft-shutdown completed (DL_ = low) Rising edge, 65mV typical hysteresis, controller disabled below this level 4.05 V3P3 0.4
32 0.4
Pulses V V 0.4 1 V A
10 4.27 4.48 V
R ON(VRHOT) Low state High-impedance state, VRHOT forced to 5V, TA = +25C VTHRM = 0 to 5V, TA = +25C Typical hysteresis = 15C VTIME - VILIM = 100mV VLIMIT VCSP_ - VCSN_ VTIME - VILIM = 500mV ILIM = VCC
VALLEY CURRENT LIMIT, DROOP, AND CURRENT BALANCE Current-Limit Threshold Voltage (Positive) Current-Limit Threshold Voltage (Negative) Accuracy Current-Limit Threshold Voltage (Zero Crossing)
VLIMIT(NEG)
VCSP_ - VCSN_, nominally -125% of VLIMIT
VZERO
VGND - VLX_, DPRSLPVR = 5V
1
mV
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5
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN1 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER CSP_, CSN_ CommonMode Input Range Phase 2 Disable Threshold CSP_, CSN_ Input Current ILIM Input Current Measured at CSP2 ICSP_, ICSN_ TA = +25C I ILIM TA = +25C (1/N) x (VCSP_ - VCSN_) at IFBAC = 0; indicates summation over all phases from 1 to N, N = 2 Gm(FBAC) TA = +25oC TA = 0 C to +85 C
o o
SYMBOL
CONDITIONS
MIN 0 3 -0.2 -0.1 -0.5 -0.75
TYP
MAX 2
UNITS V V A A mV/ phase
VCC 1
VCC 0.4 +0.2 +0.1 +0.5 +0.75
Droop Amplifier Offset
Droop Amplifier Transconductance Current-Balance Amplifier Offset Current-Balance Amplifier Transconductance
IFBAC/ [ (VCSP_ - VCSN_)]; indicates summation over all phases from 1 to N, N = 2, VFBAC = VCSN- = 0.45V to 2V (VCSP1 - VCSN1) - (VCSP2 - VCSN2) at ICCI = 0
590
600
608
S
-1.0 200
+1.0
mV S
Gm(CCI)
ICCI/[(VCSP1 - VCSN1) - (VCSP2 - VCSN2)]
CURRENT MONITOR (MAX17082/MAX17482 Only) Current-Monitor Output Current at Full Load Condition Current-Monitor Transconductance IMON Clamp Voltage IMON Pulldown Resistance in Shutdown GATE DRIVERS DH_ Gate Driver On-Resistance DL_ Gate Driver On-Resistance DH_ Gate Driver Source Current DH_ Gate Driver Sink Current DL_ Gate Driver Source Current R ON(DH_) R ON(DL_) BST_ - LX_ forced to 5V High state (pullup) Low state (pulldown) High state (pullup) Low state (pulldown) 0.9 0.7 0.7 0.25 2.2 2.7 2.7 2.5 2.0 2.0 0.7 A A A I IMON VCSP1 - VCSN1 = VCSP2 - VCSN2 = 20mV, VCSN_ = 0.45V to 2.0V I IMON/ [ (VCSP_ - VCSN_)]; indicates summation over all phases from 1 to N, N = 2, CSN_ = 0.45V to 2V I SINK = 10mA SHDN = 0, measured after soft-shutdown completed (DL_ = low) 93.12 96 98.88 A
Gm(IMON)
2.2
2.4
2.6
mS
VIMON,max
1.05
1.10 10
1.15
V
IDH_(SOURCE) DH_ forced to 2.5V, BST_ - LX_ forced to 5V IDH_(SINK) DH_ forced to 2.5V, BST_ - LX_ forced to 5V
IDL_(SOURCE) DL_ forced to 2.5V
6
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN1 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER DL_ Gate Driver Sink Current Internal BST_ Switch On-Resistance LOGIC AND I/O Logic Input High Voltage Logic Input Low Voltage SHDN No-Fault Level Low-Voltage Logic Input High Voltage VIHLV VIH VIL SHDN, PGDIN MAX17021: DPRSLPVR SHDN, PGDIN MAX17021: DPRSLPVR To enable no-fault mode PSI, D0-D6; MAX17082/MAX17482: DPRSLPVR, SLOW, MAX17021: DPRSTP PSI, D0-D6; MAX17082/MAX17482: DPRSLPVR, SLOW, MAX17021: DPRSTP TA = +25C, SHDN, DPRSLPVR, PGDIN, PSI, DPRSTP, SLOW, D0-D6 = 0 or 5V -1 11 0.67 2.3 1.0 13 V V V V SYMBOL IDL_(SINK) R ON(BST_) CONDITIONS DL_ forced to 2.5V MIN TYP 8 10 20 MAX UNITS A
MAX17021/MAX17082/MAX17482
Low-Voltage Logic Input Low Voltage Logic Input Current
VILLV
0.33
V
+1
A
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN2 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = -40C to +105C, unless otherwise noted.) (Note 4)
PARAMETER PWM CONTROLLER Input-Voltage Range VCC, VDD V3P3 DAC codes from 0.8125V to 1.5000V 4.5 3.0 -0.75 -10 -25 1.19 1.09 5.5 3.6 +0.75 +10 mV +25 1.21 1.11 V V % SYMBOL CONDITIONS MIN TYP MAX UNITS
DC Output-Voltage Accuracy
VOUT
Measured at FB with respect to GNDS; DAC codes from includes load0.3750V to 0.8000V regulation error (Note 2) DAC codes from 0 to 0.3625V MAX17021: IMVP-6+ MAX17082/MAX17482: IMVP-6.5
Boot Voltage
VBOOT
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7
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN2 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = -40C to +105C, unless otherwise noted.) (Note 4)
PARAMETER GNDS Input Range GNDS Gain TIME Regulation Voltage A GNDS VTIME VOUT/ VGNDS RTIME = 71.5k RTIME = 71.5k (12.5mV/s nominal) RTIME = 35.7k (25mV/s nominal) to 178k (5mV/s nominal) Soft-start and soft-shutdown: RTIME = 35.7k (3.125mV/s nominal) to 178k (0.625mV/s nominal) Slow: IMVP-6.5 (MAX17082/MAX17482): VSLOW = 0V, 1/2 of nominal slew rate, RTIME = 71.5k (6.25mV/s nominal); IMVP-6+ (MAX17021): VDPRSTP = VDPRSLPVR = 5V, 1/4 of nominal slew rate, RTIME = 71.5k (3.125mV/s nominal) Slow: IMVP-6.5 (MAX17082/MAX17482): VSLOW = 0V, 1/2 of nominal slew rate, RTIME = 35.7k (12.5mV/s nominal) to 178k (2.5mV/s nominal); IMVP-6+ (MAX17021): VDPRSTP = VDPRSLPVR = 5V, 1/4 of nominal slew rate, RTIME = 35.7k (6.25mV/s nominal) to 178k (1.25mV/s nominal) RTON = 96.75k 167ns nominal On-Time t ON (600kHz per phase), SYMBOL CONDITIONS MIN -200 0.97 1.985 -10 -15 TYP MAX +200 1.03 2.015 +10 +15 UNITS mV V/V V
-25
+25
TIME Slew-Rate Accuracy
-15
+15
%
-17
+17
-15 -15 -15
+15 +15 +15 350 ns %
Measured RTON = 200k (300kHz per phase), at DH_ 333ns nominal (Note 3) RTON = 303.25k (200kHz per phase), 500ns nominal Measured at DH_ (Note 3) Measured at VCC, VDPRSLPVR = 5V, FB forced above the regulation point Measured at V3P3, FB forced within the CLKEN power-good window
Minimum Off-Time BIAS CURRENTS Quiescent Supply Current (VCC) Quiescent Supply Current (V3P3)
t OFF(MIN)
ICC I3P3
5 4
mA A
8
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN2 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = -40C to +105C, unless otherwise noted.) (Note 4)
PARAMETER FAULT PROTECTION Skip mode after output reaches the regulation voltage or PWM mode, measured at FB with respect to the voltage target set by the VID code (see Table 4) VOVP Soft-start, soft-shutdown, skip mode, and output have not reached the regulation voltage, measured at FB VUVP tBOOT IMVP-6.5 (MAX17082) IMVP-6+ (MAX17021) SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX17021/MAX17082/MAX17482
250
350
mV
Output OvervoltageProtection Threshold (MAX17021/MAX7082 Only)
1.45 1.75 -450 20 3
1.55 V 1.85 -350 100 10 mV s ms
Output UndervoltageProtection Threshold CLKEN Startup Delay and Boot Time Period PWRGD Startup Delay
Measured at FB with respect to the voltage target set by the VID code (see Table 4) Measured from the time when FB reaches the boot target voltage (Note 3) Measured at startup from the time when CLKEN goes low Lower threshold, falling edge (undervoltage) Upper threshold, rising edge (overvoltage)
-350
-250 mV
CLKEN and PWRGD Threshold
Measured at FB with respect to the voltage target set by the VID code (see Table 4), 20mV hysteresis (typ)
+150
+250
CLKEN Output Low Voltage CLKEN Output High Voltage PWRGD, PHASEGD Output Low Voltage VCC Undervoltage-Lockout Threshold (UVLO) THERMAL PROTECTION VRHOT Trip Threshold VRHOT Output On-Resistance VUVLO(VCC)
Low state, ISINK = 3mA High state, I SOURCE = 3mA Low state, I SINK = 3mA Rising edge, 65mV typical hysteresis, controller disabled below this level 4.0 V3P3 0.4
0.4
V V
0.4 4.5
V V
Measured at THRM as a percentage of VCC, falling edge, typical hysteresis = 75mV R ON(VRHOT) Low state
28
32 10
%
_______________________________________________________________________________________
9
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 10V, VCC = VDD = VSHDN = VPGDIN = VPSI = VILIM = 5V, V3P3 = 3.3V, DPRSLPVR = GNDS = GND, VCSP1 = VCSN1 = VCSP2 = VCSN2 = 1.0000V, FB = FBAC, RFBAC = 3.57k from FBAC to CSN1, D6-D0 = [0101000]; MAX17082/MAX17482: VSLOW = 5V; MAX17021: DPRSTP = GND; TA = -40C to +105C, unless otherwise noted.) (Note 4)
PARAMETER SYMBOL CONDITIONS VTIME - VILIM = 100mV VLIMIT VCSP_ - VCSN_ VTIME - VILIM = 500mV ILIM = VCC CSP_, CSN_ Common-Mode Input Range Droop Amplifier Transconductance Current-Balance Amplifier Offset Gm(FBAC) IFBAC/ [ (VCSP_ - VCSN_)], indicates summation over all phases from 1 to N, N = 2, VFBAC = VCSN- = 0.45V to 2V (VCSP1 - VCSN1) - (VCSP2 - VCSN2) at ICCI = 0 MIN 7 40 19 0 TYP MAX 13 60 26 2 V mV UNITS
VALLEY CURRENT LIMIT, DROOP, AND CURRENT BALANCE Current-Limit Threshold Voltage (Positive)
585
610
S
-1.25
+1.25
mV
CURRENT MONITOR (MAX17082/MAX17482 Only) Current-Monitor Transconductance IMON Clamp Voltage GATE DRIVERS DH_ Gate Driver On-Resistance DL_ Gate Driver On-Resistance LOGIC AND I/O Logic Input High Voltage Logic Input Low Voltage Low-Voltage Logic Input High Voltage VIH VIL SHDN, PGDIN: MAX17021: DPRSLPVR SHDN, PGDIN: MAX17021: DPRSLPVR PSI, D0-D6: MAX17082/MAX17482: DPRSLPVR, SLOW MAX17021: DPRSTP PSI, D0-D6: MAX17082/MAX17482: DPRSLPVR, SLOW MAX17021: DPRSTP 0.67 2.3 1.0 V V R ON(DH_) R ON(DL_) BST_ - LX_ forced to 5V High state (pullup) Low state (pulldown) High state (pullup) Low state (pulldown) 2.5 2.0 2.0 0.7 Gm(IMON) VIMON,max I IMON/ [ (VCSP_ - VCSN_)], indicates summation over all phases from 1 to N, N = 2, VCSN_ = 0.45V to 2V I SINK = 10mA 2.2 1.05 2.6 1.15 mS V
VIHLV
V
Low-Voltage Logic Input Low Voltage
VILLV
0.33
V
Note 2: When pulse skipping, the output rises by approximately 1.5% when transitioning from continuous conduction to no load. Note 3: On-time and minimum off-time specifications are measured from 50% to 50% at the DH_ and DL_ pins, with LX_ forced to GND, BST_ forced to 5V, and a 500pF capacitor from DH_ to LX_ to simulate external MOSFET gate capacitance. Actual incircuit times might be different due to MOSFET switching speeds. Note 4: Specifications to TA = -40C and +105C are guaranteed by design and are not production tested.
10
______________________________________________________________________________________
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Typical Operating Characteristics
(Circuit of Figure 1. VIN = 12V, VCC = VDD = 5V, SHDN = VCC, D0-D6 set for 1.075V, TA = +25C, unless otherwise specified.)
OUTPUT VOLTAGE vs. LOAD CURRENT (VOUT(HFM) = 1.075V)
MAX17021 toc01
MAX17021/MAX17082/MAX17482
EFFICIENCY vs. LOAD CURRENT (VOUT(HFM) = 1.075V)
7V 90 EFFICIENCY (%)
MAX17021 toc02
OUTPUT VOLTAGE vs. LOAD CURRENT (VOUT(LFM) = 0.875V)
0.89 OUTPUT VOLTAGE (V) 0.88 0.87 0.86 0.85 0.84 SKIP MODE
MAX17021 toc03
1.15
100
0.90
OUTPUT VOLTAGE (V)
1.10
80
12V 20V
1.05
70
PWM MODE
1.00
60
0.95 0 10 20 30 40 50 LOAD CURRENT (A)
50 0.1 1.0 10.0 100.0 LOAD CURRENT (A)
0.83 0 5 10 LOAD CURRENT (A) 15 20
EFFICIENCY vs. LOAD CURRENT (VOUT(LFM) = 0.875V)
MAX17021 toc04
OUTPUT VOLTAGE vs. LOAD CURRENT (VOUT(C4) = 0.4V)
MAX17021 toc05
EFFICIENCY vs. LOAD CURRENT (VOUT(C4) = 0.4V)
7V 80 EFFICIENCY (%) 70 12V 60 50 40
MAX17021 toc06
90 7V 80 EFFICIENCY (%) 12V 70 20V
0.41
90
OUTPUT VOLTAGE (V)
0.40
60 SKIP MODE PWM MODE 50 0.1 1.0 10.0 100.0 LOAD CURRENT (A) 0.39 0 1 2 3 4 5 LOAD CURRENT (A)
20V
30 0.01 0.10
DPRSLPVR = VCC 1.00 10.00 LOAD CURRENT (A)
SWITCHING FREQUENCY vs. LOAD CURRENT
MAX17021 toc07
NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE (VOUT(HFM) = 1.075V)
MAX17021 toc08
NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE AT SKIP MODE (VOUT(HFM) = 1.075V)
MAX17021 toc09
400 350 SWITCHING FREQUENCY (kHz) 300 250 200 150 100 50 0 0 10 20 DPRSLPVR = VCC DPRSLPVR = GND 30 40 VOUT(LFM) = 0.875V VOUT(HFM) = 1.075V
100 NO-LOAD SUPPLY CURRENT (mA)
10.0 NO-LOAD SUPPLY CURRENT (mA)
75 IIN 50 ICC + IDD 25
ICC + IDD 1.0
0.1
IIN
0 6 9 12 15
DPRSLPVR = GND 18 21 24
0 6 9 12 15
DPRSLPVR = VCC 18 21 24
50
LOAD CURRENT (A)
INPUT VOLTAGE (V)
INPUT VOLTAGE AT SKIP MODE (V)
______________________________________________________________________________________
11
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Typical Operating Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, VCC = VDD = 5V, SHDN = VCC, D0-D6 set for 1.075V, TA = +25C, unless otherwise specified.)
0.8125V OUTPUT-VOLTAGE DISTRIBUTION
MAX17021 toc10
Gm(FB) TRANSCONDUCTANCE DISTRIBUTION
MAX17021 toc11
CURRENT BALANCE vs. LOAD CURRENT
60 50 VCSP_ - VCSN_ (mV) 40 30 20 10 0 0 5 10 15 20 25 30 35 40 45 50 LOAD CURRENT (A)
MAX17021 toc12
70 60 SAMPLE PERCENTAGE (%) 50 40 30 20 10
+85C +25C
SAMPLE SIZE = 100
60 50 SAMPLE PERCENTAGE (%) 40 30 20 10 0
+85C +25C
SAMPLE SIZE = 100
VOUT = 1.075V
0.6 0.5 0.4 0.3 0.2 0.1 0 VCSPN1 - VCSPN2 (mV)
0.8075
0.8085
0.8095
0.8105
0.8115
0.8125
0.8135
0.8145
0.8155
0.8165
0.8175
590
592
594
596
598
600
602
604
606
608
TRANSCONDUCTANCE (s)
OUTPUT VOLTAGE (V)
610
0
SOFT-START WAVEFORM (UP TO CLKEN)
MAX17021 toc13
SOFT-START WAVEFORM (UP TO PWRGD)
MAX17021 toc14
SHUTDOWN WAVEFORM
MAX17021 toc15
5V 0 5V 0 1.075V
A B
C 0 D 0 E 0 200s/div A. SHDN, 10V/div B. CLKEN, 10V/div C. VOUT, 500mV/div D. ILX1, 10A/div E. ILX2, 10A/div IOUT = 15A
5V 0 5V 0 5V 0 5V 0 1.075V 0
A B C D E F
5V 0 5V 0 5V 0 5V 0 1.075V
A B C D E
0 0 F G 100s/div A. SHDN, 10V/div B. CLKEN, 10V/div C. PWRGD, 10V/div D. DL_, 10V/div E. VOUT, 500mV/div F. ILX1, 10A/div G. ILX2, 10A/div
0 G 0 1ms/div A. SHDN, 10V/div B. PWRGD, 10V/div C. PHASEGD, 10V/div D. CLKEN, 10V/div E. VOUT, 1V/div F. ILX1, 10A/div G. ILX2, 10A/div IOUT = 15A
0
12
______________________________________________________________________________________
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Typical Operating Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, VCC = VDD = 5V, SHDN = VCC, D0-D6 set for 1.075V, TA = +25C, unless otherwise specified.)
LOAD TRANSIENT RESPONSE (HFM MODE)
MAX17021 toc16
MAX17021/MAX17082/MAX17482
LOAD-TRANSIENT RESPONSE (LFM MODE)
MAX17021 toc17
VID CODE CHANGE (SLOW = GND)
MAX17021 toc18
50A 10A 1.075V
A
20A A 5A
5V 0 1.075V
A
B 1V 0.875V 25A C 20A 5A 5A 20s/div A. IOUT = 10A TO 50A B. VOUT, 50mV/div C. ILX1, 10A/div D. ILX2, 10A/div A. IOUT = 5A TO 20A B. VOUT, 50mV/div D 5A 20s/div C. INDUCTOR CURRENT, 10A/div C B
B 0.975V 0 0 C
D
20s/div A. VID3, 5V/div B. VOUT, 50mV/div C. ILX1, 10A/div D. ILX2, 10A/div
VID CODE CHANGE (SLOW = VDD)
MAX17021 toc19
DYNAMIC VID CODE CHANGE (D0 = 12.5mV)
MAX17021 toc20
5V 0 1.075V
A
5V 0
A
B 0.975V
1.075V 1.0625V
B
0 0
C
5A 5A
C
D
D
20s/div A. VID3, 5V/div B. VOUT, 50mV/div C. ILX1, 10A/div D. ILX2, 10A/div A. D0, 5V/div B. VOUT, 20mV/div IOUT = 10A
20s/div C. ILX1, 10A/div D. ILX2, 10A/div
OUTPUT UNDERVOLTAGE FAULT
MAX17021 toc21
VIMON vs. LOAD CURRENT
160 A 140 120 VIMON (A) 100 80 60 D 40 20 0 DPRSLPVR = VCC DPRSLPVR = GND 0 10 20 30 40 50 60 70 80 VOUT = 1.075V
MAX17021 toc22
180
1.075V 0 5V 0 5V 0 30A
B C
0 100s/div A. VOUT, 500mV/div B. PWRGD, 10V/div C. DL_, 10V/div D. ILX1, 15A/div
VCSPN1 + VCSPN2 (mV)
______________________________________________________________________________________
13
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Typical Operating Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, VCC = VDD = 5V, SHDN = VCC, D0-D6 set for 1.075V, TA = +25C, unless otherwise specified.)
BIAS SUPPLY REMOVAL (UVLO RESPONSE)
MAX17021 toc24
OUTPUT OVERVOLTAGE WAVEFORM
MAX17021 toc23
5V 0.875V 0 5V B 0 5V C 0 0 5V 0 5V 0 10A 0 100s/div A. VOUT, 500mV/div B. DL_, 5V/div C. PWRGD, 5V/div 40s/div A. 5V BIAS SUPPLY, 5V/div B. VOUT, 500mV/div C. PWRGD, 5V/div D. DL_, 5V/div E. ILX1, 10A/div IOUT = 10A A 0.875V
A
B
C D E
Pin Description
PIN NAME FUNCTION System Power-Good Logic Input. PGDIN indicates the power status of other system rails and is used for power-supply sequencing. After power-up to the boot voltage, the output voltage remains at VBOOT, CLKEN remains high, and PWRGD remains low as long as the PGDIN stays low. When PGDIN is pulled high, the output transitions to selected VID voltage, and CLKEN is pulled low. If the system pulls PGDIN low during normal operation, the MAX17021/MAX17082/MAX17482 immediately drive CLKEN high, pull PWRGD low, and slew the output to the boot voltage (using two-phase pulse-skipping mode). The controller remains at the boot voltage until PGDIN goes high again, SHDN is toggled, or the VCC input power supply is cycled.
1
PGDIN
2
3
Input of Internal Comparator. Connect the output of a resistor- and thermistor-divider (between VCC and GND) to THRM. Select the components such that the voltage at THRM falls below 1.5V (30% of VCC) at the desired high temperature. Current-Monitor Output. The MAX17082/MAX17482 IMON output source a current that is directly proportional to the current-sense voltage as defined by: I IMON = Gm(IMON) x (VCSP_ - VCSN_) where Gm(IMON) = 2.4mS (typ). The IMON current is unidirectional (sources current out of IMON only) for positive current-sense values. For negative current-sense voltages, the IMON current is zero. Connect an external resistor between IMON and VSS_SENSE to create the desired IMON gain based on IMON the following equation: (MAX17082/ RIMON = 0.999V/(IMAX x R SENSE x Gm(IMON)) MAX17482 where IMAX is defined in the Current Monitor section of the Intel IMVP-6.5 specification and based on only) discrete increments (20A, 30A, 40A, etc.), RSENSE is the typical effective value of the current-sense element (sense resistor or inductor DCR) that is used to provide the current-sense voltage, and Gm(IMON) is the typical transconductance amplifier gain as defined in the Electrical Characteristics table. The IMON voltage is internally clamped to a maximum of 1.1V (typ). The transconductance amplifier and voltage clamp are internally compensated, so IMON cannot directly drive large capacitance values. To filter the IMON signal, use an RC filter as shown in Figure 2. IMON is pulled to ground when MAX17082/MAX17482 are in shutdown. THRM
14
______________________________________________________________________________________
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Pin Description (continued)
PIN NAME FUNCTION Valley Current-Limit Adjustment Input. The valley current-limit threshold voltage at CSP_ to CSN_ equals precisely 1/10 of the differential TIME to ILIM voltage over a 0.1V to 0.5V range (10mV to 50mV current-sense range). The negative current-limit threshold is nominally -125% of the corresponding valley current-limit threshold. Connect ILIM directly to VCC to set the default current-limit threshold setting of 22.5mV (typ) nominal. Slew-Rate Adjustment Pin. TIME regulates to 2.0V and the load current determines the slew rate of the internal error-amplifier target. The sum of the resistance between TIME and GND (RTIME) determines the nominal slew-rate: SLEW RATE = (12.5mV/s) x (71.5k /RTIME) The guaranteed RTIME range is between 35.7k and 178k . This "nominal" slew rate applies to VID transitions and to the transition from boot mode to VID. If the VID DAC inputs are clocked, the slew rate for all other VID transitions is set by the rate at which they are clocked, up to a maximum slew rate equal to the nominal slew rate defined above. The startup and shutdown slew rates are always 1/8 of nominal slew rate in order to minimize surge currents. MAX17021: If both DPRSLPVR and DPRSTP are pulled high, then the slew rate is reduced to 1/4 of nominal. MAX17082/MAX17482: If SLOW is low, then the slew rate is reduced to 1/2 of nominal. Controller Analog Bias Supply Voltage. Connect to a 4.5V to 5.5V source. Bypass to GND with 1F minimum. Current-Balance Compensation. Connect a 470pF capacitor between CCI and the positive side of the feedback remote sense. CCI is internally forced low in shutdown. Remote Feedback-Sense Input. Normally shorted to FBAC and connected to the VCC_SENSE pin of the CPU socket through the load-line gain resistor (see the FBAC pin description). FB internally connects to the error amplifier and integrator. Voltage-Positioning Transconductance Amplifier Output. Connect a resistor RFB between FBAC and the positive side of the feedback remote sense to set the DC steady-state droop based on the voltagepositioning gain requirement: RFB = RDROOP/(RSENSE x Gm(FBAC)) where RDROOP is the desired voltage-positioning slope and Gm(FBAC) = 600S (typ). RSENSE is the value of the current-sense resistors that are used to provide the (CSP_, CSN_) current-sense voltages. If lossless sensing is used, R SENSE = RL. In this case, consider making RFB a resistor network that includes an NTC thermistor to minimize the temperature dependence of the voltage-positioning slope. FBAC is high impedance in shutdown. Remote Ground-Sense Input. Normally connected to the VSS_SENSE pin of the CPU socket. GNDS internally connects to a transconductance amplifier that fine tunes the output voltage--compensating for voltage drops from the regulator ground to the load ground. Negative Current-Sense Input for Phase 2. Connect CSN2 to the negative terminal of the inductor current-sensing resistor or directly to the negative terminal of the inductor if the lossless DCR sensing method is used (see Figure 4). Positive Current-Sense Input for Phase 2. Connect CSP2 to the positive terminal of the inductor currentsensing resistor or directly to the positive terminal of the filtering capacitor used when the lossless DCR sensing method is used (see Figure 4). Short CSP2 to VCC for dedicated one-phase operation.
MAX17021/MAX17082/MAX17482
4
ILIM
5
TIME
6 7
VCC CCI
8
FB
9
FBAC
10
GNDS
11
CSN2
12
CSP2
______________________________________________________________________________________
15
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Pin Description (continued)
PIN NAME FUNCTION Shutdown Control Input. This input cannot withstand the battery voltage. Connect to VCC for normal operation. Connect to ground to put the IC into its 1A max shutdown state. During startup, the output voltage is ramped up to the boot voltage slowly at a slew rate that is 1/8 the slew rate set by the TIME resistor. During the transition from normal operation to shutdown, the output voltage is ramped down at the same slow slew rate. Forcing SHDN to 11V~13V disables both overvoltage-protection and undervoltage-protection circuits, clears the fault latch, disables transient phase overlap, and disables the BST_ charging switches. Do not connect SHDN to > 13V. Pulse-Skipping Control Input. This 1.0V logic input signal indicates power usage and sets the operating mode of MAX17021/MAX17082/MAX17482. When DPRSLPVR is forced high, the controller immediately enters the automatic pulse-skipping mode. The controller returns to forced-PWM mode when DPRSLPVR is forced low and the output is in regulation. The PWRGD upper threshold is blanked during any downward output-voltage transition that occurs when the controller is in pulse-skipping mode, and stays blanked until the transition-related PWRGD blanking period is complete and the output reaches regulation. The output overvoltage fault threshold is changed from a tracking [VID + 300mV] threshold to a fixed-default transitional OVP threshold during the period for which the PWRGD upper threshold is blanked. The MAX17082 is in two-phase pulse-skipping mode during startup and while in boot mode, but is in forced-PWM mode during the transition from boot mode to VID mode plus 20s, and during softshutdown, irrespective of the DRPSLPVR logic level. DPRSLPVR and PSI together determine the operating mode and the number of active phases as shown in the following truth table: DPRSLPVR PSI MODE AND PHASES 1 0 Very low current (one-phase pulse skipping) 1 1 Low current (approx 3A) (one-phase pulse skipping) 0 0 Intermediate power potential (one-phase PWM) 0 1 Max power potential ( two- or one-phase PWM as configured at CSP2) Power-State Indicator Input. DPRSLPVR and PSI together determine the operating mode and the number of active phases as shown in the truth table included under the PSI pin description above. Switching Frequency Setting Input. An external resistor between the input power source and TON sets the switching period (T SW = 1/f SW) per phase according to the following equation: T SW = 16.3pF x (RTON + 6.5k ) TON becomes high impedance in shutdown to reduce the input quiescent current. If the TON current is less than 10A, the MAX17021/MAX17082/MAX17482 disable the controller, set the TON open fault latch, and pull DL_ and DH_ low. 3.3V CLKEN Input Supply. V3P3 input supplies the CLKEN CMOS push-pull logic output. Connect to the system's standard 3.3V supply voltage before SHDN is pulled high for proper IMVP-6.5 operation. Clock Enable Push-Pull Logic Output. This inverted logic output indicates when the output voltage sensed at FB is in regulation. During soft-start, shutdown, and when the FB is out of regulation, the MAX17021/MAX17082/MAX17482 pull CLKEN up to V3P3. During VID transitions, the controller forces CLKEN low. Except during the power-up sequence, CLKEN is the inverse of PWRGD. See the Startup Timing Diagram (Figure 10). When in pulse-skipping mode (DPRSLPVR high), the upper CLKEN threshold is disabled. Open-Drain Power-Good Output. After output-voltage transitions, except during power-up and powerdown; if FB is in regulation then PWRGD is high impedance. During startup, PWRGD is held low and continues to be low while the part is in boot mode and until 5ms (typ) after CLKEN goes low. PWRGD is forced low in shutdown. PWRGD is forced high impedance whenever the slew-rate controller is active (output-voltage transitions). When in pulse-skipping mode (DPRSLPVR high), the upper PWRGD threshold comparator is blanked during downward transitions. A pullup resistor on PWRGD causes additional finite shutdown current.
13
SHDN
14
DPRSLPVR
15
PSI
16
TON
17
V3P3
18
CLKEN
19
PWRGD
16
______________________________________________________________________________________
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Pin Description (continued)
PIN FUNCTION Phase-Good Current-Balance Open-Drain Output. Used to signal the system that one of the two phases either has a fault condition or is not matched with the other. Detection is done by identifying the need for a large on-time difference between phases in order to achieve or move towards current PHASEGD balance. PHASEGD is low in shutdown. PHASEGD is forced high impedance whenever the slew-rate controller is active (output-voltage transitions). PHASEGD is forced high impedance while in one-phase operation (DPRSLPVR = high or PSI = low). Boost Flying-Capacitor Connection for Phase 2. BST2 provides the upper supply rail for the DH2 highBST2 side gate driver. An internal switch between VDD and BST2 charges the flying capacitor while the lowside MOSFET is on (DL2 pulled high and LX2 pulled to ground). Inductor Connection for Phase 2. LX2 is the internal lower supply rail for the DH2 high-side gate driver. LX2 Also used as an input to the controller's zero-crossing comparator for phase 2. High-Side Gate-Driver Output for Phase 2. DH2 swings from LX2 to BST2. The controller pulls DH2 low DH2 in shutdown. Low-Side Gate-Driver Output for Phase 2. DL2 swings from GND to VDD. DL2 is forced low in skip mode DL2 after detecting an inductor current zero crossing. DL2 is forced low during one-phase operation (PSI = GND or CSP2 = VCC). Open-Drain Output of Internal Comparator. VRHOT is pulled low when the voltage at THRM goes below VRHOT 1.5V (30% of VCC). VRHOT is high impedance in shutdown. Driver Supply Voltage Input. VDD is the supply voltage used to internally power the low-side gate drivers and refresh the BST_ flying capacitors during the off-times. Connect VDD to the 4.5V to 5.5V VDD system supply voltage. Bypass VDD to the system power ground with a 1F each or greater ceramic capacitor. Low-Side Gate-Driver Output for Phase 1. DL1 swings from GND to VDD. DL1 is forced high when an output DL1 overvoltage fault is detected, overriding any negative current-limit condition that might be present. DL1 is forced low after soft-shutdown or in skip mode after detecting an inductor current zero crossing. High-Side Gate-Driver Output for Phase 1. DH1 swings from LX1 to BST1. The controller pulls DH1 low DH1 in shutdown. Inductor Connection for Phase 1. LX1 is the internal lower supply rail for the DH1 high-side gate driver. LX1 Also used as an input to the controller's zero-crossing comparator for phase 1. Boost Flying-Capacitor Connection for Phase 1. BST1 provides the upper supply rail for the DH1 highBST1 side gate driver. An internal switch between VDD and BST1 charges the flying capacitor while the lowside MOSFET is on (DL1 is pulled high and LX1 is pulled to ground). IMVP-6+ Slew-Rate Select Input. This 1.0V logic input signal from the IMVP-6+ system is usually the logical complement of the DPRSLPVR signal. However, the IMVP-6+ specification supports a special slow C4 exit condition that allows both DPRSTP and DPRSLPVR to be pulled high simultaneously. When this occurs, the voltage-transition slew rate reduces to 1/4 the nominal (RTIME-based) slew rate for the duration of this logic condition. The slew rate returns to normal when either DPRSLPVR or DPRSTP DPRSTP is pulled low: (MAX17021) DPRSLPVR DPRSTP SLEW RATE 0 0 Nominal slew rate 0 1 Nominal slew rate 1 0 Nominal slew rate 1 1 Slew rate reduced to 1/4 of nominal IMVP-6.5 Slew-Rate Select Input. This 1.0V logic input signal selects between the nominal and "slow" SLOW (half of nominal rate) slew rates. When SLOW is forced high, the selected nominal slew rate is set by (MAX17082/ the TIME resistance as defined above. When SLOW is forced low, the slew rate is reduced to half the MAX17482) nominal slew rate. NAME
MAX17021/MAX17082/MAX17482
20
21 22 23 24 25
26
27 28 29 30
31
______________________________________________________________________________________
17
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Pin Description (continued)
PIN 32-38 NAME D0-D6 FUNCTION Low-Voltage VID DAC Code Input. The D0-D6 inputs do not have internal pullups. These 1.0V logic inputs are designed to interface directly with the CPU. The output voltage is set by the VID code indicated by the logic-level voltages on D0-D6 (see Table 4). Positive Current-Sense Input for Phase 1. Connect CSP1 to the positive terminal of the inductor currentsensing resistor or directly to the positive terminal of the filtering capacitor used when the lossless DCR sensing method is used (see Figure 4). Negative Current-Sense Input for Phase 1. Connect CSN1 to the negative terminal of the inductor current-sensing resistor or directly to the negative terminal of the inductor if the lossless DCR sensing method is used (see Figure 4). Under VCC UVLO conditions and after soft-shutdown is completed, CSN1 is internally pulled to GND through a 10 FET to discharge the output. Exposed Pad. Internally connected to GND. Connect to the ground plane through a thermally enhanced via. For the MAX17021/MAX17082/MAX17482, the exposed pad is the only GND connection and must be properly soldered.
39
CSP1
40
CSN1
--
EP
18
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ON OFF (VRON) 13 31 14 15 1 32 33 34 VID INPUTS 35 36 37 38 VALLEY CURRENT LIMIT SET TO ILIM VLIMIT = 0.2V x R1/(R1 + R2) SLEW RATE SET BY TIME BIAS CURRENT dV/dt = 12.5mV/s x 71.5k/(R1 + R2) 4 R2 59.0k AGND 3.3V 1.1V R3 56 17 R4 1.9k R5 10k 20 19 25 18 R6 13k VCC NTC3 100k B = 4250 AGND 3 FBAC N.C. FB GNDS GND (EP) 9 8 10 RFB 4.32k 1% C13 1000pF AGND C14 1000pF PWR AGND REMOTE-SENSE FILTERS R20 10 R22 25 VCC_SENSE R21 10 REMOTE-SENSE INPUTS VSS_SENSE R23 25 PWR CATCH RESISTORS REQUIRED WHEN CPU NOT POPULATED PHASEGD PWRGD VRHOT CLKEN LX2 DL2 THRM BST2 DH2 21 23 C8 22 0.22F 24 NLO R13 0 CSN2 V3P3 CSP2 R1 12.1k 5 SHDN DPRSTP DPRSLPVR PSI PGDIN D0 D1 D2 D3 D4 D5 D6 BST1 DH1 LX1 DL1 TON 16 30 28 C4 29 0.22F 27 NLO 39 40 7 11 12 C10 1000pF C11 0.22F C5 0.22F C6 OPEN AGND C7 0.22F R9 0 NHI VDD 26 VCC 6 R19 10 C1 1.0F AGND 5V BIAS INPUT C2 1.0F PWR RTON 200k SWITCHING FREQUENCY (fSW = 1/TSW): TSW = 16.3pF x (RTON + 6.5k) CIN PWR L1 R10 1.21k R11 1.50k
INPUT 7V TO 24V
D1 PWR
R12 20k
COUT
MAX17021
CSP1 ILIM CSN1 TIME CCI
PWR NTC1 10k B = 3380 CORE OUTPUT
DCR THERMAL COMPENSATION C9 0.22F NTC2 10k B = 3380 COUT R16 20k L2
C12 OPEN AGND
R15 1.50k
NHI
R14 1.21k
PWR
2
D1 PWR
LOAD-LINE ADJUSTMENT: RFB = RDROOP/(RSENSE x 600s)
AGND
Figure 1. Standard 2-Phase IMVP-6+ Application Circuit
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Detailed Description
Table 1 lists the component selection for standard applications. Table 2 lists component suppliers for the MAX17021/MAX17082/MAX17482/MAX17482. simple: the high-side switch on-time is determined solely by a one-shot whose period is inversely proportional to input voltage, and directly proportional to output voltage or the difference between the main and secondary inductor currents (see the On-Time One-Shot section). Another one-shot sets a minimum off-time. The on-time one-shot triggers when the error comparator goes low, the inductor current of the selected phase is below the valley current-limit threshold, and the minimum off-time one-shot times out. The controller maintains 180 out-ofphase operation by alternately triggering the main and secondary phases after the error comparator drops below the output-voltage set point.
Free-Running, Constant-On-Time PWM Controller with Input Feed-Forward
The Quick-PWM control architecture is a pseudo-fixedfrequency, constant-on-time, current-mode regulator with voltage feed-forward (Figure 3). This architecture relies on the output filter capacitor's ESR to act as the current-sense resistor, so the output ripple voltage provides the PWM ramp signal. The control algorithm is
Table 1. Component Selection for Standard Applications
DESIGN PARAMETERS CIRCUIT Input-Voltage Range Maximum Load Current (TDC Current) Transient Load Current Load Line COMPONENTS TON Resistance (RTON) Inductance (L) 200k (f SW = 300kHz) 200k (f SW = 300kHz) 200k (f SW = 300kHz) 200k (f SW = 300kHz) NEC/TOKIN MPC1055LR36 0.36H, 32A, 0.8m Siliconix 1x Si4386DY 7.8m /9.5m (typ/max) Siliconix 2x Si4642DY 3.9m /4.7m (typ/max) 4x 330F, 6m , 2.5V Panasonic EEFSX0D0D331XR 28x 10F, 6V ceramic (0805) 4x 10F, 25V ceramic (1210) NEC/TOKIN MPC1055LR36 0.36H, 32A, 0.8m Siliconix 1x Si4386DY 7.8m /9.5m (typ/max) Siliconix 2x Si4642DY 3.9m /4.7m (typ/max) 3x 330F, 6m , 2.5V Panasonic EEFSX0D0D331XR 28x 10F, 6V ceramic (0805) 4x 10F, 25V ceramic (1210) NEC/TOKIN MPC1055LR36 0.36H, 32A, 0.8m Siliconix 1x Si4386DY 7.8m /9.5m (typ/max) Siliconix 2x Si4642DY 3.9m /4.7m (typ/max) 4x 330F, 6m , 2.5V Panasonic EEFSX0D0D331XR 28x 10F, 6V ceramic (0805) 4x 10F, 25V ceramic (1210) NEC/TOKIN MPC1055LR36 0.36H, 32A, 0.8m Siliconix 1x Si4386DY 7.8m /9.5m (typ/max) Siliconix 2x Si4642DY 3.9m /4.7m (typ/max) 3x 330F, 6m , 2.5V Panasonic EEFSX0D0D331XR 28x 10F, 6V ceramic (0805) 4x 10F, 25V ceramic (1210) IMVP-6+ SV FIGURE 1 7V to 20V 44A (34A) 35A (10A/s) -2.1mV/A IMVP-6+ LV FIGURE 1 7V to 20V 23A (19A) 18A (10A/s) -4mV/A IMVP-6.5 AUBURNDALE SV CORE FIGURE 2 7V to 20V 50A (37A) 35A (10A/s) -1.9mV/A IMVP-6.5 AUBURNDALE LV CORE FIGURE 2 7V to 20V 28A (19A) 23A (10A/s) -3mV/A
High-Side MOSFET (NH) Low-Side MOSFET (NL)
Output Capacitors (COUT)
Input Capacitors (CIN)
20
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Table 1. Component Selection for Standard Applications (continued)
DESIGN PARAMETERS TIME-ILIM Resistance (R1) ILIM-GND Resistance (R2) FB Resistance (RFB) IMON Resistance LX_-CSP_ Resistance CSP_-CSN_ Series Resistance (R6) Parallel NTC Resistance DCR Sense NTC (NTC1) DCR Sense Capacitance (CSENSE) IMVP-6+ SV IMVP-6+ LV IMVP-6.5 AUBURNDALE SV CORE 10k 59k 4.02k 9.09k 1.21k 1.50k 20k 10k NTC B = 3380 TDK NTCG163JH103F 2x 0.22F, 6V ceramic (0805) IMVP-6.5 AUBURNDALE LV CORE 10k 59k 6.34k 18.2k 1.21k 1.50k 20k 10k NTC B = 3380 TDK NTCG163JH103F 2x 0.22F, 6V ceramic (0805)
10k 59k 4.32k N/A 1.21k 1.50k 20k 10k NTC B = 3380 TDK NTCG163JH103F 2x 0.22F, 6V ceramic (0805)
10k 59k 8.45k N/A 1.21k 1.50k 20k 10k NTC B = 3380 TDK NTCG163JH103F 2x 0.22F, 6V ceramic (0805)
Table 2. Component Suppliers
SUPPLIER AVX Corp. BI Technologies Central Semiconductor Corp. Fairchild Semiconductor International Rectifier KEMET Corp NEC/TOKIN Corp. Panasonic Corp. WEBSITE www.avxcorp.com www.bitechnologies.com www.centralsemi.com www.fairchildsemi.com www.irf.com www.kemet.com www.nec-tokin.com www.panasonic.com SUPPLIER Pulse Engineering Renesas Technology Corp. SANYO Electric Co, Ltd. Siliconix (Vishay) Sumida Taiyo Yuden TDK Corp. TOKO America, Inc. WEBSITE www.pulseeng.com www.renesas.com www.sanyodevice.com www.vishay.com www.sumida.com www.t-yuden.com www.component.tdk.com www.tokoam.com
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ON OFF (VRON) 13 14 31 AGND 15 1 32 33 34 VID INPUTS 35 36 37 38 VALLEY CURRENT LIMIT SET TO ILIM VLIMIT = 0.2V x R1/(R1 + R2) SLEW RATE SET BY TIME BIAS CURRENT dV/dt = 12.5mV/s x 71.5k/(R1 + R2) 4 R2 59.0k AGND 17 R1 12.1k 5 ILIM TIME SHDN DPRSLPVR SLOW PSI PGDIN D0 D1 D2 D3 D4 D5 D6 BST1 DH1 LX1 DL1 TON 16 30 28 C4 29 0.22F 27 NLO 39 40 7 11 12 C10 1000pF C11 0.22F C5 0.22F C6 OPEN AGND C7 0.22F R9 0 NHI RTON 200k VDD 26 VCC 6 R19 10 C1 1.0F AGND 5V BIAS INPUT C2 1.0F PWR SWITCHING FREQUENCY (fSW = 1/TSW): TSW = 16.3pF x (RTON + 6.5k) CIN PWR L1 INPUT 7V TO 24V
D1 PWR
MAX17082 MAX17482
CSP1 CSN1 CCI V3P3 CSN2 CSP2
R10 1.21k R11 1.50k
R12 20k
COUT
PWR NTC1 10k B = 3380 CORE OUTPUT
DCR THERMAL COMPENSATION C9 0.22F NTC2 10k B = 3380 COUT R16 20k L2
3.3V 1.1V R3 56 R4 1.9k R5 10k
20 19 25 18 R6 13k 2
PHASEGD PWRGD VRHOT CLKEN THRM BST2 DH2 LX2 DL2 21 23
R13 0
C12 OPEN AGND
R15 1.50k R14 1.21k
C8 22 0.22F 24 NLO
NHI
PWR
VCC NTC3 100k B = 4250
D1 PWR
AGND R7 4.7k C15 0.022F VSS_SENSE GND (EP) 3
LOAD-LINE ADJUSTMENT: RFB = RDROOP/(RSENSE x 600s) IMON 9 8 10 RFB 4.02k 1% C13 1000pF AGND C14 1000pF PWR AGND REMOTE-SENSE FILTERS R20 10 R22 25 VCC_SENSE R21 10 REMOTE-SENSE INPUTS VSS_SENSE R23 25 PWR CATCH RESISTORS REQUIRED WHEN CPU NOT POPULATED
FBAC FB GNDS
R8 9.09k
AGND
Figure 2. Standard 2-Phase IMVP-6.5 (Calpella) Application Circuit
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
THRM VRHOT BST2
MAX17021 (MAX17082/MAX17482)
DH2 EN2 SECONDARY PHASE DRIVERS LX2 DL2 GND BLANK
0.3 x VCC CSP2 CSN2 CSP1 CSN1 ILIM TIME Q 10x MINIMUM OFF-TIME TRIG ONE-SHOT PHASE 1 ON-TIME ONE-SHOT REF (2.0V) GND D0-D6 DAC PGDIN SHDN Q Q T GND LX1 1mV R-TO-I CONVERTER SLEW R Q S S Q R MAIN PHASE DRIVERS Q TRIG FB Gm(CCI) CSN1 10x Q TRIG CURRENTBALANCE FAULT 5ms STARTUP DELAY
PHASEGD
ONE-SHOT PHASE 2 ON-TIME
CCI
200k CSN2 CSP2 CSP1
Gm(CCI)
VCC
TON
BST1 DH1 LX1
FAULT
TARGET
VDD
SKIP
DL1
GND TARGET - 300mV FB TARGET + 200mV 5ms STARTUP DELAY 60s STARTUP DELAY BLANK (MAX17082/ MAX17482) CSP_ x2 IMON V3P3 CLKEN PWRGD
GNDS
SLEW
MODE/PHASE/ SLEW-RATE CONTROL FBAC x2 Gm(FB) CSP_
DPRSLPVR
DPRSTP
SKIP
EN2
(SLOW)
PGDIN
CSN_
CSN_
Gm(IMON)
Figure 3. Functional Diagram
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PSI
Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Dual 180 Out-of-Phase Operation
The two phases in the MAX17021/MAX17082/ MAX17482 operate 180 out-of-phase to minimize input and output filtering requirements, reduce electromagnetic interference (EMI), and improve efficiency. This effectively lowers component count--reducing cost, board space, and component power requirements--making the MAX17021/MAX17082/MAX17482 ideal for high-power, cost-sensitive applications. Typically, switching regulators provide power using only one phase instead of dividing the power among several phases. In these applications, the input capacitors must support high instantaneous current requirements. The high RMS ripple current can lower efficiency due to I2R power loss associated with the input capacitor's effective series resistance (ESR). Therefore, the system typically requires several lowESR input capacitors in parallel to minimize input-voltage ripple, to reduce ESR-related power losses, and to meet the necessary RMS ripple current rating. With the MAX17021/MAX17082/MAX17482, the controller shares the current between two phases that operate 180 out-of-phase, so the high-side MOSFETs never turn on simultaneously during normal operation. The instantaneous input current of either phase is effectively halved, resulting in reduced input-voltage ripple, ESR power loss, and RMS ripple current (see the Input Capacitor Selection section). Therefore, the same performance can be achieved with fewer or less-expensive input capacitors. enable signal (SHDN going from low to high) must be delayed until the battery voltage is present to ensure startup.
Switching Frequency (TON)
Connect a resistor (RTON) between TON and VIN to set the switching period TSW = 1/fSW, per phase: TSW = 16.3pF x (RTON + 6.5k) A 96.75k to 303.25k corresponds to switching periods of 167ns (600kHz) to 500ns (200kHz), respectively. High-frequency (600kHz) operation optimizes the application for the smallest component size, trading off efficiency due to higher switching losses. This might be acceptable in ultra-portable devices where the load currents are lower and the controller is powered from a lower voltage supply. Low-frequency (200kHz) operation offers the best overall efficiency at the expense of component size and board space.
+5V Bias Supply (VCC and VDD) The Quick-PWM controller requires an external +5V bias supply in addition to the battery. Typically, this +5V bias supply is the notebook's 95% efficient +5V system supply. Keeping the bias supply external to the IC improves efficiency and eliminates the cost associated with the +5V linear regulator that would otherwise be needed to supply the PWM circuit and gate drivers. If stand-alone capability is needed, the +5V bias supply can be generated with an external linear regulator. The +5V bias supply must provide V CC (PWM controller) and VDD (gate-drive power), so the maximum current drawn is: IBIAS = ICC + fSW (QG(LOW) + QG(HIGH))
where ICC is provided in the Electrical Characteristics table, fSW is the switching frequency, and QG(LOW) and Q G(HIGH) are the MOSFET data sheet's total gatecharge specification limits at VGS = 5V. VIN and VDD can be tied together if the input power source is a fixed +4.5V to +5.5V supply. If the +5V bias supply is powered-up prior to the battery supply, the
24
TON Open-Circuit Protection The TON input includes open-circuit protection to avoid long, uncontrolled on-times that could result in an overvoltage condition on the output. The MAX17021/ MAX17082/MAX17482 detect an open-circuit fault if the TON current drops below 10A for any reason--the TON resistor (RTON) is unpopulated, a high resistance value is used, the input voltage is low, etc. Under these conditions, the MAX17021/MAX17082/MAX17482 stop switching (DH_ and DL_ pulled low) and immediately set the fault latch. Toggle SHDN or cycle the V CC power supply below 0.5V to clear the fault latch and reactivate the controller. On-Time One-Shot The core of each phase contains a fast, low-jitter, adjustable one-shot that sets the high-side MOSFETs on-time. The one-shot for the main phase varies the ontime in response to the input and feedback voltages. The main high-side switch on-time is inversely proportional to the input voltage as measured by the TON input, and proportional to the feedback voltage (VFB):
tON(MAIN) = TSW ( VFB + 0.075V ) VIN
where the switching period (TSW = 1/fSW) is set by the resistor at the TON pin, and 0.075V is an approximation to accommodate the expected drop across the lowside MOSFET switch. The one-shot for the secondary phase varies the ontime in response to the input voltage and the difference between the main and secondary inductor currents. Two identical transconductance amplifiers integrate the
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
difference between the master and slave current-sense signals. The summed output is internally connected to CCI, allowing adjustment of the integration time constant with a compensation network connected between CCI and FB. The resulting compensation current and voltage are determined by the following equations: ICCI = Gm(VCSP1 - VCSN1) - Gm(VCSP2 - VCSN2) VCCI = VFB + ICCIZCCI where ZCCI is the impedance at the CCI output. The secondary on-time one-shot uses this integrated signal (VCCI) to set the secondary high-side MOSFETs ontime. When the main and secondary current-sense signals (VCM = VCSP1 - VCSN1 and VCS = VCSP2 - VCSN2) become unbalanced, the transconductance amplifiers adjust the secondary on-time, which increases or decreases the secondary inductor current until the current-sense signals are properly balanced:
V + 0.075V tON(SEC) = TSW CCI VIN V + 0.075V ICCIZCCI 7 = TSW FB + TSW V VIN IN
tor current reverses at light- or negative-load currents. With reversed inductor current, the inductor's EMF causes LX_ to go high earlier than normal, extending the on-time by a period equal to the DH_-rising dead time. For loads above the critical conduction point, where the dead-time effect is no longer a factor, the actual switching frequency (per phase) is: fSW =
MAX17021/MAX17082/MAX17482
( VOUT + VDIS ) tON ( VIN + VDIS - VCHG )
where VDIS is the sum of the parasitic voltage drops in the inductor discharge path, including synchronous rectifier, inductor, and PCB resistances; VCHG is the sum of the parasitic voltage drops in the inductor charge path, including high-side switch, inductor, and PCB resistances; and tON is the on-time as determined above.
Current Sense
The output current of each phase is sensed. Low-offset amplifiers are used for current balance, voltage-positioning gain, and current limit. Sensing the current at the output of each phase offers advantages, including less noise sensitivity, more accurate current sharing between phases, and the flexibility of using either a current-sense resistor or the DC resistance of the output inductor. Using the DC resistance (RDCR) of the output inductor allows higher efficiency. In this configuration, the initial tolerance and temperature coefficient of the inductor's DCR must be accounted for in the output-voltage droop-error budget and power monitor. This currentsense method uses an RC filtering network to extract the current information from the output inductor (see Figure 4). The resistive divider used should provide a current-sense resistance (RCS) low enough to meet the current-limit requirements, and the time constant of the RC network should match the inductor's time constant (L/RCS): R2 RCS = R R1 + R2 DCR and: RCS = L 1 1 + CEQ R1 R2
= (Main On-time) + ( Secondary Current Balance Correction) t
This algorithm results in a nearly constant switching frequency and balanced inductor currents despite the lack of a fixed-frequency clock generator. The benefits of a constant switching frequency are twofold: first, the frequency can be selected to avoid noise-sensitive regions such as the 455kHz IF band; second, the inductor ripple-current operating point remains relatively constant, resulting in easy design methodology and predictable output-voltage ripple. The on-time oneshots have good accuracy at the operating points specified in the Electrical Characteristics table. Ontimes at operating points far removed from the conditions specified in the Electrical Characteristics table can vary over a wider range. On-times translate only roughly to switching frequencies. The on-times guaranteed in the Electrical Characteristics table are influenced by switching delays in the external high-side MOSFET. Resistive losses, including the inductor, both MOSFETs, output capacitor ESR, and PCB copper losses in the output and ground tend to raise the switching frequency at higher output currents. Also, the dead-time effect increases the effective on-time, reducing the switching frequency. It occurs only during forced-PWM operation and dynamic output-voltage transitions when the induc-
where RCS is the required current-sense resistance and RDCR is the inductor's series DC resistance.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Use the worst-case inductance and RDCR values provided by the inductor manufacturer, adding some margin for the inductance drop over temperature and load. To minimize the current-sense error due to the currentsense inputs' bias current (ICSP_ and ICSN_), choose R1||R2 to be less than 2k and use the previous equation to determine the sense capacitance (CEQ). Choose capacitors with 5% tolerance and resistors with 1% tolerance specifications. Temperature compensation is recommended for this current-sense method. See the Voltage Positioning and Loop Compensation section for detailed information. When using a current-sense resistor for accurate outputvoltage positioning, the circuit requires a differential RC filter to eliminate the AC voltage step caused by the equivalent series inductance (LESL) of the current-sense resistor (see Figure 4). The ESL induced-voltage step does not affect the average current-sense voltage, but results in a significant peak current-sense voltage error that results in unwanted offsets in the regulation voltage and results in early current-limit detection. Similar to the inductor DCR sensing method above, the RC filter's time constant should match the L/R time constant formed by the current-sense resistor's parasitic inductance: LESL = CEQR1 RSENSE where LESL is the equivalent series inductance of the current-sense resistor, RSENSE is current-sense resistance value, and CEQ and R1 are the time-constant matching components.
INPUT (VIN) CIN
DH_ LX_
NH L
SENSE RESISTOR LESL RSENSE COUT LSENSE RSENSE
MAX17021 DL_ MAX17082 MAX17482
PGND CSP_ CSN_
NL
DL R1
CEQR1 =
CEQ
A) OUTPUT SERIES RESISTOR SENSING INPUT (VIN) CIN
DH_ LX_
NH INDUCTOR L RDCR RCS = NL DL COUT R1 R2 RDCR = L 11 + CEQ R1 R2
MAX17021 DL_ MAX17082 MAX17482
PGND CSP_ CSN_
(
R2 R1 + R2
)
RDCR
[
]
CEQ FOR THERMAL COMPENSATION: R2 SHOULD CONSIST OF AN NTC RESISTOR IN SERIES WITH A STANDARD THIN-FILM RESISTOR.
B) LOSSLESS INDUCTOR SENSING
Figure 4. Current-Sense Methods
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Current Balance The MAX17021/MAX17082/MAX17482 integrate the difference between the current-sense voltages and adjust the on-time of the secondary phase to maintain current balance. The current balance now relies on the accuracy of the current-sense resistors instead of the inaccurate, thermally sensitive on-resistance of the low-side MOSFETs. With active current balancing, the current mismatch is determined by the current-sense resistor values and the offset voltage of the transconductance amplifiers:
VOS(IBAL) IOS(IBAL) = ILMAIN - ILSEC = RSENSE where RSENSE is the effective sense resistance seen at the current-sense pins and VOS(IBAL) is the current-balance offset specification in the Electrical Characteristics table. The worst-case current mismatch occurs immediately after a load transient due to inductor value mismatches resulting in different di/dt for the two phases. The time it takes the current-balance loop to correct the transient imbalance depends on the mismatch between the inductor values and switching frequency. cuit, this current-limit method is effective in almost every circumstance. The positive valley current-limit threshold voltage at CSP_ to CSN_ equals precisely 1/10 of the differential TIME to ILIM voltage over a 0.1V to 0.5V range (10mV to 50mV current-sense range). Connect ILIM directly to VCC to set the default current-limit threshold setting of 22.5mV (typ). The negative current-limit threshold (forced-PWM mode only) is nominally -125% of the corresponding valley current-limit threshold. When the inductor current drops below the negative current limit, the controller immediately activates an on-time pulse--DL_ turns off, and DH_ turns on--allowing the inductor current to remain above the negative-current threshold. Carefully observe the PCB layout guidelines to ensure that noise and DC errors do not corrupt the current-sense signals seen by the current-sense inputs (CSP_, CSN_).
MAX17021/MAX17082/MAX17482
Feedback Adjustment Amplifiers
Voltage-Positioning Amplifier (Steady-State Droop) The MAX17021/MAX17082/MAX17482 include a transconductance amplifier for adding gain to the voltage-positioning sense path. The amplifier's input is generated by summing the current-sense inputs, which differentially sense the voltage across either currentsense resistors or the inductor's DCR. The amplifier's output connects directly to the regulator's voltage-positioned feedback input (FB), so the resistance between FB and the output-voltage sense point determines the voltage-positioning gain: VOUT = VTARGET - RFB|FB where the target voltage (VTARGET) is defined in the Nominal Output-Voltage Selection section, and the FB amplifier's output current (IFB) is determined by the sum of the current-sense voltages:
IFB = Gm(FB) VCSX
X =1 PH
Current Limit The current-limit circuit employs a unique "valley" current-sensing algorithm that uses current-sense resistors between the current-sense inputs (CSP_ to CSN_) as the current-sensing elements. If the current-sense signal of the selected phase is above the current-limit threshold, the PWM controller does not initiate a new cycle until the inductor current of the selected phase drops below the valley current-limit threshold. When either phase trips the current limit, both phases are effectively current limited since the interleaved controller does not initiate a cycle with either phase. Since only the valley current is actively limited, the actual peak current is greater than the current-limit threshold by an amount equal to the inductor ripple current. Therefore, the exact current-limit characteristic and maximum load capability are a function of the currentsense resistance, inductor value, and battery voltage. When combined with the undervoltage-protection cir-
where VCS = VCSP_ - VCSN_ is the differential currentsense voltage, and G m(FB) is typically 600S as defined in the Electrical Characteristics table.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Differential Remote Sense The MAX17021/MAX17082/MAX17482 include differential, remote-sense inputs to eliminate the effects of voltage drops along the PCB traces and through the processor's power pins. The feedback-sense node connects to the voltage-positioning resistor (R FB ). The ground-sense (GNDS) input connects to an amplifier that adds an offset directly to the target voltage, effectively adjusting the output voltage to counteract the voltage drop in the ground path. Connect the voltage-positioning resistor (RFB), and ground-sense (GNDS) input directly to the processor's remote-sense outputs, as shown in Figure 1. Integrator Amplifier An integrator amplifier forces the DC average of the FB voltage to equal the target voltage. This transconductance amplifier integrates the feedback voltage and provides a fine adjustment to the regulation voltage (Figure 3), allowing accurate DC output-voltage regulation regardless of the output ripple voltage. The integrator amplifier has the ability to shift the output voltage by 100mV (typ). The differential input-voltage range is at least 60mV total, including DC offset and AC ripple.
The MAX17021/MAX17082/MAX17482 disable the integrator by connecting the amplifier inputs together at the beginning of all VID transitions done in pulse-skipping mode (DPRSLPVR = high). The integrator remains disabled until 20s after the transition is completed (the internal target settles) and the output is in regulation (edge detected on the error comparator). the response time. After either high-side MOSFET turns off, if the output voltage does not exceed the regulation voltage when the minimum off-time expires, the controller simultaneously turns on both high-side MOSFETs during the next on-time cycle. This maximizes the total inductor current slew rate. The phases remain overlapped until the output voltage exceeds the regulation voltage after the minimum off-time expires. After the phase-overlap mode ends, the controller automatically begins with the opposite phase. For example, if the secondary phase provided the last on-time pulse before overlap operation began, the controller starts switching with the main phase when overlap operation ends. Table 3 is the operating mode truth table.
Nominal Output-Voltage Selection
The nominal no-load output voltage (V TARGET ) is defined by the selected voltage reference (VID DAC) plus the remote ground-sense adjustment (VGNDS) as defined in the following equation: VTARGET = VFB = VDAC + VGNDS where VDAC is the selected VID voltage. On startup, the MAX17021/MAX17082/MAX17482 slew the target voltage from ground to the preset boot voltage.
Transient-Overlap Operation
When a transient occurs, the response time of the controller depends on how quickly it can slew the inductor current. Multiphase controllers that remain 180 out-ofphase when a transient occurs actually respond slower than an equivalent single-phase controller. To provide fast-transient response, the MAX17021/MAX17082/ MAX17482 support a phase-overlap mode, which allows the dual regulators to operate in-phase when heavy load transients are detected, effectively reducing
DAC Inputs (D0-D6) The digital-to-analog converter (DAC) programs the output voltage using the D0-D6 inputs. D0-D6 are lowvoltage (1.0V) logic inputs, designed to interface directly with the CPU. Do not leave D0-D6 unconnected. Changing D0-D6 initiates a transition to a new outputvoltage level. Change D0-D6 together, avoiding greater than 20ns skew between bits. Otherwise, incorrect DAC readings might cause a partial transition to the wrong voltage level followed by the intended transition to the correct voltage level, lengthening the overall transition time. The available DAC codes and resulting output voltages are compatible with the IMVP-6/IMVP-6+ and IMVP-6.5 (Table 4) specifications.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Table 3. Operating Mode Truth Table
INPUTS SHDN GND DPRSTP DPRSLPVR (SLOW) X X PSI X PHASE OPERATION* Disabled Multiphase pulse-skipping 1/8 RTIME slew rate Multiphase forced-PWM nominal RTIME slew rate 1-phase forcedPWM nominal RTIME slew rate OPERATING MODE
Low-Power Shutdown Mode. DL1 and DL2 forced low, and the controller is disabled. The supply current drops to 1A (max). Startup/Boot. When SHDN is pulled high, the MAX17021/ MAX17082/MAX17482 begin the startup sequence. The controller enables the PWM regulator and ramps the output voltage up to the boot voltage. See Figure 10.
Rising
X
X
X
High
X (High)
Low
High
Full Power. The no-load output voltage is determined by the selected VID DAC code (D0-D6, Table 4).
High
X (High)
Low
Low
Intermediate Power. The no-load output voltage is determined by the selected VID DAC code (D0-D6, Table 4). When PSI is pulled low, the MAX17021/MAX17082/MAX17482 immediately disable phase 2. DH2 and DL2 are pulled low. Deeper Sleep Mode. The no-load output voltage is determined by the selected VID DAC code (D0-D6, Table 4). When DPRSLPVR is pulled high, the MAX17021/MAX17082/MAX17482 immediately enter one-phase pulse-skipping operation, allowing automatic PWM/PFM switchover under light loads. The PWRGD and CLKEN upper thresholds are blanked during downward transitions. DH2 and DL2 are pulled low. Deeper Sleep Slow Exit Mode. The no-load output voltage is determined by the selected VID DAC code (D0-D6, Table 4). When DPRSTP is pulled high while DPRSLPVR is already high, the MAX17021 remains in one-phase pulse-skipping operation, allowing automatic PWM/PFM switchover under light loads, but reduces its slew rate to 1/4 of normal. When SLOW is pulled low, the MAX17082/MAX17482 reduce their slew rate to 1/2 of normal. The PWRGD and CLKEN upper thresholds are blanked. DH2 and DL2 are pulled low. Shutdown. When SHDN is pulled low, the MAX17021/MAX17082/ MAX17482 immediately pull PWRGD and PHASEGD low, CLKEN becomes high, all enabled phases are activated, and the output voltage is ramped down to ground. Once the output reaches 0V, the controller enters the low-power shutdown state. See Figure 10. Fault Mode. The fault latch has been set by the MAX17021/ MAX17082/MAX17482 UVP or thermal-shutdown protection, or by the OVP protection. The controller remains in fault mode until VCC power is cycled or SHDN toggled.
High
Low (High)
High
X
1-phase pulseskipping nominal RTIME slew rate
High
High (Low)
High
X
1-phase pulseskipping
Falling
X
X
X
Multiphase forced-PWM 1/8 RTIME slew rate
High
X
X
X
Disabled
*Multiphase operation--all enabled phases active.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Table 4. IMVP-6+/IMVP-6.5 Output-Voltage VID DAC Codes
D6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 1 D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 1 D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 OUTPUT VOLTAGE (V) 1.5000 1.4875 1.4750 1.4625 1.4500 1.4375 1.4250 1.4125 1.4000 1.3875 1.3750 1.3625 1.3500 1.3375 1.3250 1.3125 1.3000 1.2875 1.2750 1.2625 1.2500 1.2375 1.2250 1.2125 1.2000 1.1875 1.1750 1.1625 1.1500 1.1375 1.1250 1.1125 1.1125 D6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 1 D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 1 D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 OUTPUT VOLTAGE (V) 0.7000 0.6875 0.6750 0.6625 0.6500 0.6375 0.6250 0.6125 0.6000 0.5875 0.5750 0.5625 0.5500 0.5375 0.5250 0.5125 0.5000 0.4875 0.4750 0.4625 0.4500 0.4375 0.4250 0.4125 0.4000 0.3875 0.3750 0.3625 0.3500 0.3375 0.3250 0.3125 0.3125
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Table 4. IMVP-6+/IMVP-6.5 Output-Voltage VID DAC Codes (continued)
D6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 OUTPUT VOLTAGE (V) 1.1000 1.0875 1.0750 1.0625 1.0500 1.0375 1.0250 1.0125 1.0000 0.9875 0.9750 0.9625 0.9500 0.9375 0.9250 0.9125 0.9000 0.8875 0.8750 0.8625 0.8500 0.8375 0.8250 0.8125 0.8000 0.7875 0.7750 0.7625 0.7500 0.7375 0.7250 0.7125 D6 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 OUTPUT VOLTAGE (V) 0.3000 0.2875 0.2750 0.2625 0.2500 0.2375 0.2250 0.2125 0.2000 0.1875 0.1750 0.1625 0.1500 0.1375 0.1250 0.1125 0.1000 0.0875 0.0750 0.0625 0.0500 0.0375 0.0250 0.0125 0 0 0 0 0 0 0 0
*D6-D0 = 1111111 is an OFF code for the MAX17082/MAX17482. The MAX17082/MAX17482 enter the shutdown sequence if the OFF code is set, forcing PWRGD and PHASEGD low, and forcing CLKEN high. Exit from the OFF code follows the startup sequence. If the OFF code is present when SHDN is pulled high, the MAX17082/MAX17482 remain off.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Suspend Mode When the processor enters low-power deeper sleep mode, the IMVP-6 CPU sets the VID DAC code to a lower output voltage and drives DPRSLPVR high. The MAX17021/MAX17082/MAX17482 respond by slewing the internal target voltage to the new DAC code, switching to single-phase operation, and letting the output voltage gradually drift down to the deeper sleep voltage. During the transition, the MAX17021/MAX17082/ MAX17482 blank both the upper and lower PWRGD and CLKEN thresholds until 20s after the internal target reaches the deeper sleep voltage. Once the 20s timer expires, the MAX17021/MAX17082/MAX17482 reenable the lower PWRGD and CLKEN threshold, but keep the upper threshold blanked until the output voltage reaches the regulation level. PHASEGD remains blanked high impedance while DPRSLPVR is high.
dynamic VID transitions, the transition time (tTRAN) is given by: t TRAN = VNEW - VOLD (dVTARGET dt)
where dVTARGET/dt = 12.5mV/s x 71.5k/RTIME is the slew rate, VOLD is the original output voltage, and VNEW is the new target voltage. See TIME Slew Rate Accuracy in Electrical Characteristics for slew-rate limits. For soft-start and shutdown, the controller automatically reduces the slew rate to 1/8. The output voltage tracks the slewed target voltage, making the transitions relatively smooth. The average inductor current per phase required to make an outputvoltage transition is: IL COUT x (dVTARGET dt ) TOTAL
Output-Voltage-Transition Timing
The MAX17021/MAX17082/MAX17482 perform mode transitions in a controlled manner, automatically minimizing input surge currents. This feature allows the circuit designer to achieve nearly ideal transitions, guaranteeing just-in-time arrival at the new output-voltage level with the lowest possible peak currents for a given output capacitance. At the beginning of an output-voltage transition, the MAX17021/MAX17082/MAX17482 blank both PWRGD thresholds, preventing the PWRGD open-drain output from changing states during the transition. The controller enables the lower PWRGD threshold approximately 20s after the slew-rate controller reaches the target output voltage, but the upper PWRGD threshold remains blanked until the output voltage reaches the regulation level if the controller enters pulse-skipping operation. The slew rate (set by resistor RTIME) must be set fast enough to ensure that the transition can be completed within the maximum allotted time. The MAX17021/MAX17082/MAX17482 automatically control the current to the minimum level required to complete the transition in the calculated time. The slewrate controller uses an internal capacitor and current source programmed by RTIME to transition the output voltage. The total transition time depends on RTIME, the voltage difference, and the accuracy of the slew-rate controller (C SLEW accuracy). The slew rate is not dependent on the total output capacitance, as long as the surge current is less than the current limit. For all
where dVTARGET/dt is the required slew rate, COUT is the total output capacitance, and TOTAL is the number of active phases.
Deeper Sleep Transitions When DPRSLPVR goes high, the MAX17021/MAX17082/ MAX17482 immediately disable phase 2 (DH2 and DL2 forced low), blank PHASEGD high impedance, and enter pulse-skipping operation (see Figures 5 and 6). If the VIDs are set to a lower voltage setting, the output drops at a rate determined by the load and the output capacitance. The internal target still ramps as before, and PWRGD remains blanked high impedance until 20s after the output voltage reaches the internal target. * Fast C4E Deeper Sleep Exit: When exiting deeper sleep (DPRSLPVR pulled low) while the output voltage still exceeds the deeper sleep voltage, the MAX17021/MAX17082/MAX17482 quickly slew (50mV/s min regardless of RTIME setting) the internal target voltage to the DAC code provided by the processor as long as the output voltage is above the new target. The controller remains in skip mode until the output voltage equals the internal target. Once the internal target reaches the output voltage, phase 2 is enabled. The controller blanks PWRGD, PHASEGD, and CLKEN until 20s after the transition is completed. See Figure 5.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
* Standard C4 Deeper Sleep Exit: When exiting deeper sleep (DPRSLPVR pulled low) while the output voltage is regulating to the deeper sleep voltage, the MAX17021/MAX17082/MAX17482 immediately activate all enabled phases and ramp the output voltage to the LFM DAC code provided by the processor at the slew rate set by RTIME. The controller blanks PWRGD, PHASEGD, and CLKEN until 20s after the transition is completed. See Figure 6. * IMVP-6+ Slow C4 Deeper Sleep Exit: When exiting deeper sleep (DPRSLPVR high, DPRSTP pulled high) while the output voltage is regulating to the deeper sleep voltage, the MAX17021 remains in 1phase skip mode and ramps the output voltage to the LFM DAC code provided by the processor at 1/4 the slew rate set by RTIME. The controller blanks PWRGD, PHASEGD, and CLKEN until 20s after the transition is completed. See Figure 7.
MAX17021/MAX17082/MAX17482
ACTUAL VOUT CPU CORE VOLTAGE VID (D0-D6) DPRSLPVR DPRSTP PSI INTERNAL PWM CONTROL DH1 DH2 PWRGD CLKEN PHASEGD OVP (MAX17021/ MAX17082 ONLY) BLANK HIGH IMPEDANCE BLANK LOW BLANK HIGH THRESHOLD ONLY BLANK HIGH THRESHOLD ONLY BLANK HIGH IMPEDANCE (1-PHASE OPERATION) SET TO DEFAULT tBLANK 20s TYP tBLANK 20s TYP TRACKS INTERNAL TARGET BLANK HIGH IMPEDANCE BLANK LOW DO NOT CARE (DPRSLPVR DOMINATES STATE) 1-PHASE SKIP (DH1 ACTIVE, DH2 = DL2 = FORCED LOW) NO PULSES: VOUT > VTARGET FORCED PWM INTERNAL TARGET DEEPER SLEEP VID
Figure 5. C4E (C4 Early Exit) Transition
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ACTIVE VID CPU CORE VOLTAGE VID (D0-D6) DPRSLPVR DPRSTP PSI INTERNAL PWM CONTROL DH1 DH2 DO NOT CARE (DPRSLPVR DOMINATES STATE) 1-PHASE SKIP (DH1 ACTIVE, DH2 = DL2 = FORCED LOW) NO PULSES: VOUT > VTARGET 1-PHASE FORCED PWM INTERNAL TARGET ACTUAL VOUT LFM VID DPRSLP VID LFM VID
DEEPER SLEEP VID
PWRGD
BLANK HIGH- IMPEDANCE
BLANK HIGH THRESHOLD ONLY
BLANK HIGH IMPEDANCE BLANK LOW
CLKEN
BLANK LOW
BLANK HIGH THRESHOLD ONLY
PHASEGD OVP (MAX17021/ MAX17082 ONLY)
BLANK HIGH IMPEDANCE (1-PHASE OPERATION)
SET TO DEFAULT tBLANK 20s TYP
TRACKS INTERNAL TARGET tBLANK 20s TYP
Figure 6. Standard C4 Transition
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
ACTIVE VID CPU CORE VOLTAGE VID (D0-D6) DPRSLPVR DPRSTP PSI INTERNAL PWM CONTROL DH1 DH2 PWRGD BLANK HIGH IMPEDANCE BLANK HIGH THRESHOLD ONLY BLANK HIGH IMPEDANCE BLANK LOW DO NOT CARE (DPRSLPVR DOMINATES STATE) 1-PHASE SKIP (DH1 ACTIVE, DH2 = DL2 = FORCED LOW) NO PULSES: VOUT > VTARGET 1-PHASE FORCED PWM INTERNAL TARGET ACTUAL VOUT SLOW SLEW RATE LFM VID DPRSLP VID LFM VID SLOW SLEW RATE
DEEPER SLEEP VID
CLKEN
BLANK LOW
BLANK HIGH THRESHOLD ONLY BLANK HIGH IMPEDANCE (1-PHASE OPERATION)
PHASEGD OVP (MAX17021/ MAX17082 ONLY) SET TO DEFAULT TRACKS INTERNAL TARGET
tBLANK 20s TYP
tBLANK 20s TYP
Figure 7. Slow C4 Transition
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
CPU FREQ
CPU LOAD
VID (D0-D6)
CPU CORE VOLTAGE PSI INTERNAL PWM CONTROL 2-PHASE PWM 1-PHASE PWM 2-PHASE PWM
PWRGD CLKEN PHASEGD
BLANK HIGH IMPEDANCE BLANK LOW BLANK HIGH IMPEDANCE tBLANK 20s typ
BLANK HIGH IMPEDANCE BLANK LOW
tBLANK 20s typ 32 SWITCHING CYCLES ON DH2
Figure 8. PSI Transition
PSI Transitions When PSI is pulled low, the MAX17021/MAX17082/ MAX17482 immediately disable phase 2 (DH2 and DL2 forced low), blank PHASEGD high impedance, and enter single-phase PWM operation (see Figure 8). When PSI is pulled high, the MAX17021/MAX17082/ MAX17482 enable phase 2. PHASEGD is blanked high impedance for 32 switching cycles on DH2, allowing sufficient time/cycles for phases 1 and 2 to achieve current balance. In a typical IMVP-6 application, the VID is reduced by 1 LSB (12.5mV) when PSI is pulled low, and increased by 1 LSB when PSI is pulled high.
forms to constantly be the complement of the high-side gate-drive waveforms. This keeps the switching frequency constant and allows the inductor current to reverse under light loads, providing fast, accurate negative output-voltage transitions by quickly discharging the output capacitors. Forced-PWM operation comes at a cost: the no-load 5V bias supply current remains between 10mA to 50mA per phase, depending on the external MOSFETs and switching frequency. To maintain high efficiency under light-load conditions, the processor can switch the controller to a low-power pulse-skipping control scheme after entering suspend mode. PSI determines how many phases are active when operating in forced-PWM mode (DPRSLPVR = low). When PSI is pulled low, the main phase remains active but the secondary phase is disabled (DH2 and DL2 forced low).
Forced-PWM Operation (Normal Mode)
During soft-shutdown, and normal operation--when the CPU is actively running (DPRSLPVR = low)--the MAX17021/MAX17082/MAX17482 operate with the lownoise, forced-PWM control scheme. Forced-PWM operation disables the zero-crossing comparators of all active phases, forcing the low-side gate-drive wave36
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Light-Load Pulse-Skipping Operation (Deeper Sleep)
When DPRSLPVR is pulled high, the MAX17021/ MAX17082/MAX17482 operate with a single-phase pulse-skipping mode. The pulse-skipping mode enables the driver's zero-crossing comparator, so the controller pulls DL1 low when it detects zero inductor current. This keeps the inductor from discharging the output capacitors and forces the controller to skip pulses under light-load conditions to avoid overcharging the output. During downward transitions in pulse-skipping operation, the controller temporarily sets the OVP threshold to default, preventing false OVP faults when the transition to pulse-skipping operation coincides with a VID code change. Once the error amplifier detects that the output voltage is in regulation, the OVP threshold tracks the selected VID DAC code. The MAX17021/MAX17082/ MAX17482 automatically use forced-PWM operation during soft-shutdown, regardless of the DPRSLPVR and PSI configuration. The switching waveforms might appear noisy and asynchronous when light loading activates pulse-skipping operation, but this is a normal operating condition that results in high light-load efficiency. Trade-offs between PFM noise and light-load efficiency are made by varying the inductor value. Generally, low inductor values produce a broader efficiency vs. load curve, while higher values result in higher full-load efficiency (assuming that the coil resistance remains fixed) and less output-voltage ripple. Penalties for using higher inductor values include larger physical size and degraded load-transient response, especially at low input-voltage levels.
MAX17021/MAX17082/MAX17482
Automatic Pulse-Skipping Switchover In skip mode (DPRSLPVR = high), an inherent automatic switchover to PFM takes place at light loads (Figure 9). This switchover is affected by a comparator that truncates the low-side switch on-time at the inductor current's zero crossing. The zero-crossing comparator senses the inductor current across the low-side MOSFETs. Once VLX drops below the zero-crossing comparator threshold (see the Electrical Characteristics table), the comparator forces DL_ low. This mechanism causes the threshold between pulse-skipping PFM and nonskipping PWM operation to coincide with the boundary between continuous and discontinuous inductor-current operation. The PFM/PWM crossover occurs when the load current of each phase is equal to 1/2 the peak-to-peak ripple current, which is a function of the inductor value (Figure 9). For a battery input range of 7V to 20V, this threshold is relatively constant, with only a minor dependence on the input voltage due to the typically low duty cycles. The total load current at the PFM/PWM crossover threshold (I LOAD(SKIP) ) is approximately:
T V V -V ILOAD(SKIP) = TOTAL SW OUT IN OUT L VIN where TOTAL is the number of active phases.
INDUCTOR CURRENT
i t
VBATT - VOUT L
IPEAK
ILOAD = IPEAK/2
0 ON-TIME TIME
Figure 9. Pulse-Skipping/Discontinuous Crossover Point
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Power-Up Sequence (POR, UVLO)
The MAX17021/MAX17082/MAX17482 are enabled when SHDN is driven high (Figure 10). The internal reference powers up first. Once the reference exceeds its UVLO threshold, the internal analog blocks are turned on and masked by a 50s one-shot delay. The PWM controller is then enabled. Power-on reset (POR) occurs when VCC rises above approximately 2V, resetting the fault latch and preparing the controller for operation. The VCC UVLO circuitry inhibits switching until VCC rises above 4.25V. The controller powers up the reference once the system enables the controller, VCC is above 4.25V, and SHDN is driven high. With the reference in regulation, the controller ramps the output voltage to the boot voltage (1.2V for MAX17021 IMVP-6+ and 1.1V for MAX17082/ MAX17482 IMVP-6.5) at 1/8 the slew rate set by RTIME: t TRAN(START) = 8VBOOT ( dVTARGET dt) current limit, so full output current is available immediately. CLKEN is pulled low approximately 60s after the MAX17021/MAX17082/MAX17482 reach the boot voltage if PGDIN is high. At the same time, the MAX17021/ MAX17082/MAX17482 slew the output to the voltage set at the VID inputs at the programmed slew rate. PWRGD and PHASEGD become high impedance approximately 5ms after CLKEN is pulled low. The MAX17021/ MAX17082/MAX17482 automatically use forced-PWM operation during soft-start and soft-shutdown, regardless of the DPRSLPVR and PSI configuration. For automatic startup, the battery voltage should be present before VCC. If the controller attempts to bring the output into regulation without the battery voltage present, the fault latch trips. The controller remains shut down until the fault latch is cleared by toggling SHDN or cycling the VCC power supply below 0.5V. If the VCC voltage drops below 4.25V, the controller assumes that there is not enough supply voltage to make valid decisions. To protect the output from overvoltage faults, the controller shuts down immediately and forces a high-impedance output.
where dVTARGET/dt = 12.5mV/s x 71.5k/RTIME is the slew rate. The soft-start circuitry does not use a variable
VCC
SHDN INVALID CODE VBOOT INVALID CODE SOFT-SHUTDOWN = 1/8 SLEW RATE SET BY RTIME
VID (D0-D6) SOFT-START = 1/8 SLEW RATE SET BY RTIME
VCORE
INTERNAL PWM CONTROL
SKIP
FORCED PWM
FORCED PWM
PHASEGD CLKEN PWRGD tBLANK 60s TYP tBLANK 20s TYP tBLANK 5ms TYP tBLANK 60s TYP
Figure 10. Power-Up and Shutdown Sequence Timing Diagram
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
Shutdown
When SHDN goes low, the MAX17021/MAX17082/ MAX17482 enter low-power shutdown mode. PWRGD is pulled low immediately, and the output voltage ramps down at 1/8 the slew rate set by RTIME: 8VOUT t TRAN(SHDN) = (dVTARGET dt) where dVTARGET/dt = 12.5mV/s x 71.5k/RTIME is the slew rate. Slowly discharging the output capacitors by slewing the output over a long period of time keeps the average negative inductor current low (damped response), thereby eliminating the negative output-voltage excursion that occurs when the controller discharges the output quickly by permanently turning on the low-side MOSFET (underdamped response). This eliminates the need for the Schottky diode normally connected between the output and ground to clamp the negative output-voltage excursion. After the controller reaches the zero target, the MAX17021/ MAX17082/MAX17482 shut down completely--the drivers are disabled (DL1 and DL2 driven low) and the supply current drops below 1A. When a fault condition--output UVLO or thermal shutdown--activates the shutdown sequence, the protection circuitry sets the fault latch to prevent the controller from restarting. To clear the fault latch and reactivate the controller, toggle SHDN or cycle VCC power below 0.5V. increments (10A, 20A, 30A, 40A, etc.), RSENSE is the typical effective value of the current-sense element (sense resistor or inductor DCR) that is used to provide the current-sense voltage, and Gm(IMON) is the typical transconductance amplifier gain as defined in the Electrical Characteristics table. The IMON voltage is internally clamped to a maximum of 1.1V (typ), preventing the IMON output from exceeding the IMON voltage rating even under overload or short-circuit conditions. When the controller is disabled, IMON is pulled to ground. To filter the IMON signal, use an RC filter as shown in Figure 2. The filter time constant is (R7 + R8) x C15.
MAX17021/MAX17082/MAX17482
Phase Fault (PHASEGD)
The MAX17021/MAX17082/MAX17482 include a phasefault output that signals the system that one of the two phases either has a fault condition or is not matched with the other. Detection is done by identifying the need for a large on-time difference between phases in order to achieve or move towards current balance. PHASEGD is high impedance when the controller operates in one-phase mode (DPRSLPVR high or PSI low and DPRSLPVR low). On exit to two-phase mode, PHASEGD is forced high impedance for 32 switching cycles on DH2. PHASEGD is low in shutdown. PHASEGD is forced high impedance whenever the slew-rate controller is active (output-voltage transitions).
Current Monitor (IMON) (MAX17021/MAX17482 Only)
The MAX17082/MAX17482 includes a unidirectional transconductance amplifier that sources current proportional to the positive current-sense voltage. The IMON output current is defined by: IIMON = Gm(IMON) x (VCSP_ - VCSN_) where Gm(IMON) = 2.4mS (typ) and the IMON current is unidirectional (sources current out of IMON only) for positive current-sense values. For negative currentsense voltages, the IMON current is zero. The current monitor allows the processor to accurately monitor the CPU load and quickly calculate the power dissipation to determine if the system is about to overheat before the significantly slower temperature sensor signals an over-temperature alert. Connect an external resistor between IMON and VSS_SENSE to create the desired IMON gain based on the following equation: RIMON = 0.999V/(IMAX x RSENSE x Gm(IMON)) where IMAX is defined in the Current Monitor section of the Intel IMVP-6.5 specification and based on discrete
Temperature Comparator (VRHOT)
The MAX17021/MAX17082/MAX17482 also feature an independent comparator with an accurate threshold (VHOT) that tracks the analog supply voltage (VHOT = 0.3VCC). This makes the thermal trip threshold independent of the VCC supply voltage tolerance. Use a resistor- and thermistor-divider between VCC and GND to generate a voltage-regulator over-temperature monitor. Place the thermistor as close to the MOSFETs and inductors as possible.
Fault Protection (Latched)
Output Overvoltage Protection (MAX17021/MAX17082 Only) The overvoltage-protection (OVP) circuit is designed to protect the CPU against a shorted high-side MOSFET by drawing high current and blowing the battery fuse. The MAX17021/MAX17082 continuously monitor the output for an overvoltage fault. The controller detects an OVP fault if the output voltage exceeds the set VID DAC voltage by more than 300mV, regardless of the operating state. During downward transitions in
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
pulse-skipping operation (DPRSLPVR = high), the OVP threshold is set to default. When the OVP circuit detects an overvoltage fault, the MAX17021/MAX17082 immediately force DL1 high and pull DH1 and DH2 low. This action turns on the synchronous-rectifier MOSFETs with 100% duty and, in turn, rapidly discharges the output filter capacitor and forces the output low. If the condition that caused the overvoltage (such as a shorted high-side MOSFET) persists, the battery fuse will blow. Toggle SHDN or cycle the VCC power supply below 0.5V to clear the fault latch and reactivate the controller. Overvoltage protection can be disabled through the nofault test mode (see the No-Fault Test Mode section).
MOSFET Gate Drivers
The DH_ and DL_ drivers are optimized for driving moderate-sized high-side and larger low-side power MOSFETs. This is consistent with the low duty factor seen in notebook applications, where a large V IN V OUT differential exists. The high-side gate drivers (DH_) source and sink 2.2A, and the low-side gate drivers (DL_) source 2.7A and sink 8A. This ensures robust gate drive for high-current applications. The DH_ floating high-side MOSFET drivers are powered by internal boost switch charge pumps at BST_, while the DL_ synchronous-rectifier drivers are powered directly by the 5V bias supply (VDD). Adaptive dead-time circuits monitor the DL_ and DH_ drivers and prevent either FET from turning on until the other is fully off. The adaptive driver dead time allows operation without shoot-through with a wide range of MOSFETs, minimizing delays and maintaining efficiency. There must be a low-resistance, low-inductance path from the DL_ and DH_ drivers to the MOSFET gates for the adaptive dead-time circuits to work properly; otherwise, the sense circuitry in the MAX17021/MAX17082/ MAX17482 interprets the MOSFET gates as off while charge actually remains. Use very short, wide traces (50 mils to 100 mils wide if the MOSFET is 1in from the driver). The internal pulldown transistor that drives DL_ low is robust, with a 0.25 (typ) on-resistance. This helps prevent DL_ from being pulled up due to capacitive coupling from the drain to the gate of the low-side MOSFETs when the inductor node (LX_) quickly switches from ground to VIN. Applications with high input voltages and long inductive driver traces might require rising LX_ edges do not pull up the low-side MOSFETs' gate, causing shoot-through currents. The capacitive coupling between LX_ and DL_ created by the MOSFET's gate-to-drain capacitance (CRSS), gateto-source capacitance (CISS - CRSS), and additional board parasitics should not exceed the following minimum threshold: C VGS(TH) > VIN RSS CISS Typically, adding a 4700pF between DL_ and power ground (C NL in Figure 11), close to the low-side MOSFETs, greatly reduces coupling. Do not exceed 22nF of total gate capacitance to prevent excessive turn-off delays.
Output Undervoltage Protection (UVP) If the MAX17021/MAX17082/MAX17482 output voltage is 400mV below the target voltage, the controller activates the shutdown sequence and sets the fault latch. Once the controller ramps down to zero, it forces DL1 and DL2 high, and pulls DH1 and DH2 low. Toggle SHDN or cycle the VCC power supply below 0.5V to clear the fault latch and reactivate the controller. UVP can be disabled through the no-fault test mode (see the No-Fault Test Mode section). Thermal-Fault Protection The MAX17021/MAX17082/MAX17482 feature a thermal-fault-protection circuit. When the junction temperature rises above +160C, a thermal sensor sets the fault latch and activates the soft-shutdown sequence. Once the controller ramps down to zero, it forces DL1 and DL2 high, and pulls DH1 and DH2 low. Toggle SHDN or cycle the VCC power supply below 0.5V to clear the fault latch and reactivate the controller after the junction temperature cools by 15C.
Thermal shutdown can be disabled through the no-fault test mode (see the No-Fault Test Mode section).
No-Fault Test Mode The latched fault-protection features can complicate the process of debugging prototype breadboards since there are (at most) a few milliseconds in which to determine what went wrong. Therefore, a no-fault test mode is provided to disable the fault protection--overvoltage protection, undervoltage protection, and thermal shutdown. Additionally, the test mode clears the fault latch if it has been set. The no-fault test mode is entered by forcing 11V to 13V on SHDN.
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* Input-voltage range: The maximum value (VIN(MAX)) must accommodate the worst-case high AC adapter voltage. The minimum value (VIN(MIN)) must account for the lowest input voltage after drops due to connectors, fuses, and battery selector switches. If there is a choice at all, lower input voltages result in better efficiency. Maximum load current: There are two values to consider. The peak load current (ILOAD(MAX)) determines the instantaneous component stresses and filtering requirements, and thus drives output capacitor selection, inductor saturation rating, and the design of the current-limit circuit. The continuous load current (ILOAD) determines the thermal stresses and thus drives the selection of input capacitors, MOSFETs, and other critical heat-contributing components. Modern notebook CPUs generally exhibit ILOAD = ILOAD(MAX) x 80%. For multiphase systems, each phase supports a fraction of the load, depending on the current balancing. When properly balanced, the load current is evenly distributed among each phase: I ILOAD(PHASE) = LOAD TOTAL where TOTAL is the total number of active phases. Switching frequency: This choice determines the basic trade-off between size and efficiency. The optimal frequency is largely a function of maximum input voltage, due to MOSFET switching losses that are proportional to frequency and VIN2. The optimum frequency is also a moving target due to rapid improvements in MOSFET technology that are making higher frequencies more practical. Inductor operating point: This choice provides trade-offs between size vs. efficiency and transient response vs. output noise. Low inductor values provide better transient response and smaller physical size, but also result in lower efficiency and higher output noise due to increased ripple current. The minimum practical inductor value is one that causes the circuit to operate at the edge of critical conduction (where the inductor current just touches zero with every cycle at maximum load). Inductor values lower than this grant no further size-reduction benefit. The optimum operating point is usually found between 20% and 50% ripple current.
MAX17021/MAX17082/MAX17482
BST_
(RBST_)* INPUT (VIN)
DH_ LX_
CBST_
NH L
*
CBYP VDD
DL_ (CNL)* PGND
NL
*
(RBST_)* OPTIONAL--THE RESISTOR LOWERS EMI BY DECREASING THE SWITCHING NODE RISE TIME. (CNL)* OPTIONAL--THE CAPACITOR REDUCES LX_ TO DL_ CAPACITIVE COUPLING THAT CAN CAUSE SHOOT-THROUGH CURRENTS.
*
Figure 11. Gate Drive Circuit
Alternatively, shoot-through currents can be caused by a combination of fast high-side MOSFETs and slow lowside MOSFETs. If the turn-off delay time of the low-side MOSFETs are too long, the high-side MOSFETs can turn on before the low-side MOSFETs have actually turned off. Adding a resistor less than 5 in series with BST_ slows down the high-side MOSFET turn-on time, eliminating the shoot-through currents without degrading the turn-off time (RBST_ in Figure 11). Slowing down the high-side MOSFET also reduces the LX_ node rise time, thereby reducing EMI and high-frequency coupling responsible for switching noise.
*
Multiphase Quick-PWM Design Procedure
Firmly establish the input-voltage range and maximum load current before choosing a switching frequency and inductor operating point (ripple-current ratio). The primary design trade-off lies in choosing a good switching frequency and inductor operating point, and the following four factors dictate the rest of the design:
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Inductor Selection
The switching frequency and operating point (% ripple current or LIR) determine the inductor value as follows: VOUT VIN - VOUT L = TOTAL fSWILOAD(MAX)LIR VIN where TOTAL is the total number of phases. Find a low-loss inductor having the lowest possible DC resistance that fits in the allotted dimensions. Ferrite cores are often the best choice, although powdered iron is inexpensive and can work well at 200kHz. The core must be large enough not to saturate at the peak inductor current (IPEAK): ILOAD(MAX) LIR IPEAK = 1+ 2 TOTAL
Setting the Current Limit
The minimum current-limit threshold must be high enough to support the maximum load current when the current limit is at the minimum tolerance value. The valley of the inductor current occurs at ILOAD(MAX) minus half the ripple current; therefore: ILOAD(MAX) LIR ILIMIT(LOW) > 1- 2 TOTAL where TOTAL is the total number of active phases, and ILIMIT(LOW) equals the minimum current-limit threshold voltage divided by the current-sense resistor (RSENSE).
Output Capacitor Selection
The output filter capacitor must have low-enough effective series resistance (ESR) to meet output ripple and load-transient requirements, yet have high enough ESR to satisfy stability requirements. In CPU VCORE converters and other applications where the output is subject to large-load transients, the output capacitor's size typically depends on how much ESR is needed to prevent the output from dipping too low under a load transient. Ignoring the sag due to finite capacitance:
Transient Response
The inductor ripple current impacts transient-response performance, especially at low VIN - VOUT differentials. Low inductor values allow the inductor current to slew faster, replenishing charge removed from the output filter capacitors by a sudden load step. The amount of output sag is also a function of the maximum duty factor, which can be calculated from the on-time and minimum off-time. For a dual-phase controller, the worst-case output sag voltage can be determined by:
VOUT TSW M + tOFF(MIN) VIN + VSAG = ( VIN - 2VOUT ) TSW 2COUT VOUT - 2tOFF(MIN) VIN L ILOAD(MAX)
(RESR + RPCB ) I
VSTEP
LOAD(MAX)
(
)2
ILOAD(MAX) VOUT TSW + tOFF(MIN) 2COUT VIN
where t OFF(MIN) is the minimum off-time (see the Electrical Characteristics table). The amount of overshoot due to stored inductor energy can be calculated as: VSOAR
In non-CPU applications, the output capacitor's size often depends on how much ESR is needed to maintain an acceptable level of output ripple voltage. The output ripple voltage of a step-down controller equals the total inductor ripple current multiplied by the output capacitor's ESR. When operating multiphase systems out-ofphase, the peak inductor currents of each phase are staggered, resulting in lower output ripple voltage by reducing the total inductor ripple current. For multiphase operation, the maximum ESR to meet ripple requirements is: VINfSWL RESR VRIPPLE ( VIN - TOTAL VOUT ) VOUT where TOTAL is the total number of active phases and fSW is the switching frequency per phase. The actual capacitance value required relates to the physical size needed to achieve low ESR, as well as to the chemistry of the capacitor technology. Thus, the capacitor is usually selected by ESR and voltage rating rather than by capacitance value (this is true of polymer types).
( ILOAD(MAX) )2 L
2TOTAL COUT VOUT
where TOTAL is the total number of active phases.
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When using low-capacity ceramic filter capacitors, capacitor size is usually determined by the capacity needed to prevent V SAG and V SOAR from causing problems during load transients. Generally, once enough capacitance is added to meet the overshoot requirement, undershoot at the rising load edge is no longer a problem (see the VSAG and VSOAR equations in the Transient Response section). Their relatively low capacitance value can cause output overshoot when stepping from full-load to no-load conditions, unless a small inductor value is used (high switching frequency) to minimize the energy transferred from inductor to capacitor during load-step recovery. Unstable operation manifests itself in two related but distinctly different ways: double pulsing and feedbackloop instability. Double pulsing occurs due to noise on the output or because the ESR is so low that there is not enough voltage ramp in the output-voltage signal. This "fools" the error comparator into triggering a new cycle immediately after the minimum off-time period has expired. Double pulsing is more annoying than harmful, resulting in nothing worse than increased output ripple. However, it can indicate the possible presence of loop instability due to insufficient ESR. Loop instability can result in oscillations at the output after line or load steps. Such perturbations are usually damped, but can cause the output voltage to rise above or fall below the tolerance limits. The easiest method for checking stability is to apply a very fast zero-to-max load transient and carefully observe the output-voltage-ripple envelope for overshoot and ringing. It can help to simultaneously monitor the inductor current with an AC current probe. Do not allow more than one cycle of ringing after the initial step-response under/overshoot.
MAX17021/MAX17082/MAX17482
Output Capacitor Stability Considerations
For Quick-PWM controllers, stability is determined by the value of the ESR zero relative to the switching frequency. The boundary of instability is given by the following equation: f fESR SW where: fESR = and: REFF = RESR + RDROOP + RPCB where COUT is the total output capacitance, RESR is the total equivalent series resistance, RDROOP is the voltage-positioning gain, and RPCB is the parasitic board resistance between the output capacitors and sense resistors. For a standard 300kHz application, the ESR zero frequency must be well below 95kHz, preferably below 50kHz. Tantalum, SANYO POSCAP, and Panasonic SP capacitors in widespread use at the time of publication have typical ESR zero frequencies below 50kHz. In the standard application circuit, the ESR needed to support a 30mVP-P ripple is 30mV/(40A x 0.3) = 2.5m. Four 330F/2.5V Panasonic SP (type SX) capacitors in parallel provide 1.5m (max) ESR. With a 2m droop and 0.5m PCB resistance, the typical combined ESR results in a zero at 30kHz. Ceramic capacitors have a high-ESR zero frequency, but applications with significant voltage positioning can take advantage of their size and low ESR. Do not put high-value ceramic capacitors directly across the output without verifying that the circuit contains enough voltage positioning and series PCB resistance to ensure stability. When only using ceramic output capacitors, output overshoot (VSOAR) typically determines the minimum output capacitance requirement. 1 2REFF COUT
Input Capacitor Selection
The input capacitor must meet the ripple current requirement (IRMS) imposed by the switching currents. The multiphase Quick-PWM controllers operate out-ofphase while the Quick-PWM slave controllers provide selectable out-of-phase or in-phase on-time triggering. Out-of-phase operation reduces the RMS input current by dividing the input current between several staggered stages. For duty cycles less than 100%/OUTPH per phase, the IRMS requirements can be determined by the following equation:
I IRMS = LOAD TOTAL VOUT ( VIN - TOTAL VOUT ) TOTAL VIN
where TOTAL is the total number of out-of-phase switching regulators. The worst-case RMS current requirement occurs when operating with V IN = 2TOTALVOUT. At this point, the above equation simplifies to IRMS = 0.5 x ILOAD/TOTAL.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
For most applications, nontantalum chemistries (ceramic, aluminum, or OS-CON) are preferred due to their resistance to inrush surge currents typical of systems with a mechanical switch or connector in series with the input. If the Quick-PWM controller is operated as the second stage of a two-stage power-conversion system, tantalum input capacitors are acceptable. In either configuration, choose an input capacitor that exhibits less than +10C temperature rise at the RMS input current for optimal circuit longevity. Generally, a small high-side MOSFET is desired to reduce switching losses at high input voltages. However, the RDS(ON) required to stay within package power dissipation often limits how small the MOSFET can be. Again, the optimum occurs when the switching losses equal the conduction (RDS(ON)) losses. Highside switching losses do not usually become an issue until the input is greater than approximately 15V. Calculating the power dissipation in high-side MOSFET (NH) due to switching losses is difficult since it must allow for difficult quantifying factors that influence the turn-on and turn-off times. These factors include the internal gate resistance, gate charge, threshold voltage, source inductance, and PCB layout characteristics. The following switching-loss calculation provides only a very rough estimate and is no substitute for breadboard evaluation, preferably including verification using a thermocouple mounted on NH: VIN(MAX)ILOAD fSW QG(SW) PD (NH Switching) = I TOTAL GATE C V 2f + OSS IN SW 2 where COSS is the NH MOSFET's output capacitance, Q G(SW) is the charge needed to turn on the N H MOSFET, and IGATE is the peak gate-drive source/sink current (2.2A typ). Switching losses in the high-side MOSFET can become an insidious heat problem when maximum AC adapter voltages are applied due to the squared term in the C x VIN2 x SW switching-loss equation. If the high-side MOSFET chosen for adequate RDS(ON) at low-battery voltages becomes extraordinarily hot when biased from V IN(MAX) , consider choosing another MOSFET with lower parasitic capacitance. For the low-side MOSFET (NL), the worst-case power dissipation always occurs at maximum input voltage:
2 V I PD (NL Re sistive) = 1- OUT LOAD RDS(ON) VIN(MAX) TOTAL
Power-MOSFET Selection
Most of the following MOSFET guidelines focus on the challenge of obtaining high load-current capability when using high-voltage (> 20V) AC adapters. Lowcurrent applications usually require less attention. The high-side MOSFET (NH) must be able to dissipate the resistive losses plus the switching losses at both V IN(MIN) and V IN(MAX) . Calculate both these sums. Ideally, the losses at VIN(MIN) should be approximately equal to losses at V IN(MAX) , with lower losses in between. If the losses at VIN(MIN) are significantly higher than the losses at VIN(MAX), consider increasing the size of NH (reducing RDS(ON) but with higher CGATE). Conversely, if the losses at VIN(MAX) are significantly higher than the losses at VIN(MIN), consider reducing the size of NH (increasing RDS(ON) to lower CGATE). If V IN does not vary over a wide range, the minimum power dissipation occurs where the resistive losses equal the switching losses. Choose a low-side MOSFET that has the lowest possible on-resistance (RDS(ON)), comes in a moderate-sized package (i.e., one or two 8-pin SOs, DPAK, or D2PAK), and is reasonably priced. Make sure that the DL_ gate driver can supply sufficient current to support the gate charge and the current injected into the parasitic gateto-drain capacitor caused by the high-side MOSFET turning on; otherwise, cross-conduction problems might occur (see the MOSFET Gate Drivers section).
MOSFET Power Dissipation
Worst-case conduction losses occur at the duty factor extremes. For the high-side MOSFET (NH), the worstcase power dissipation due to resistance occurs at the minimum input voltage: V I PD (NH Re sistive) = OUT LOAD RDS(ON) VIN TOTAL where TOTAL is the total number of phases.
2
The worst case for MOSFET power dissipation occurs under heavy overloads that are greater than ILOAD(MAX) but are not quite high enough to exceed
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
the current limit and cause the fault latch to trip. To protect against this possibility, you can over design the circuit to tolerate: I ILOAD = TOTAL IVALLEY(MAX) + INDUCTOR 2 ILOAD(MAX)LIR = TOTALIVALLEY(MAX) + 2 where I VALLEY(MAX) is the maximum valley current allowed by the current-limit circuit, including threshold tolerance and on-resistance variation. The MOSFETs must have a good-size heatsink to handle the overload power dissipation. Choose a Schottky diode (DL) with a forward voltage low enough to prevent the low-side MOSFET body diode from turning on during the dead time. Select a diode that can handle the load current per phase during the dead times. This diode is optional and can be removed if efficiency is not critical.
Current-Balance Compensation (CCI)
The current-balance compensation capacitor (CCCI) integrates the difference between the main and secondary current-sense voltages. The internal compensation resistor (R CCI = 200k) improves transient response by increasing the phase margin. This allows the dynamics of the current-balance loop to be optimized. Excessively large capacitor values increase the integration time constant, resulting in larger current differences between the phases during transients. Excessively small capacitor values allow the current loop to respond cycle-by-cycle, but can result in small DC current variations between the phases. For most applications, a 470pF capacitor from CCI to the switching regulator's output works well. Connecting the compensation network to the output (VOUT) allows the controller to feed-forward the outputvoltage signal, especially during transients.
MAX17021/MAX17082/MAX17482
Voltage Positioning and Loop Compensation
Voltage positioning dynamically lowers the output voltage in response to the load current, reducing the output capacitance and processor's power-dissipation requirements. The controller uses a transconductance amplifier to set the transient and DC output-voltage droop (Figure 3) as a function of the load. This adjustability allows flexibility in the selected current-sense resistor value or inductor DCR, and allows smaller current-sense resistance to be used, reducing the overall power dissipated.
Boost Capacitors
The boost capacitors (CBST_) must be selected large enough to handle the gate-charging requirements of the high-side MOSFETs. Typically, 0.1F ceramic capacitors work well for low-power applications driving medium-sized MOSFETs. However, high-current applications driving large, high-side MOSFETs require boost capacitors larger than 0.1F. For these applications, select the boost capacitors to avoid discharging the capacitor more than 200mV while charging the highside MOSFETs' gates: CBST _ = N x QGATE 200mV
Steady-State Voltage Positioning Connect a resistor (RFB) between FB and VOUT to set the DC steady-state droop (load line) based on the required voltage-positioning slope (RDROOP):
RFB = RDROOP RSENSEGm(FB)
where N is the number of high-side MOSFETs used for one regulator, and QGATE is the gate charge specified in the MOSFET's data sheet. For example, assume (2) IRF7811W n-channel MOSFETs are used on the high side. According to the manufacturer's data sheet, a single IRF7811W has a maximum gate charge of 24nC (VGS = 5V). Using the above equation, the required boost capacitance would be: CBST_ = 2 x 24nC = 0.24F 200mV
Selecting the closest standard value, this example requires a 0.22F ceramic capacitor.
where the effective current-sense resistance (RSENSE) depends on the current-sense method (see the Current Sense section), and the voltage-positioning amplifier's transconductance (G m(FB) ) is typically 600S as defined in the Electrical Characteristics table. The controller sums together the input signals of the currentsense inputs (CSP_, CSN_). When the inductors' DCR is used as the current-sense element (RSENSE = RDCR), each current-sense input should include an NTC thermistor to minimize the temperature dependence of the voltage-positioning slope.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Minimum Input-Voltage Requirements and Dropout Performance
The output-voltage-adjustable range for continuousconduction operation is restricted by the nonadjustable minimum off-time one-shot and the number of phases. For best dropout performance, use the slower (200kHz) on-time settings. When working with low input voltages, the duty-factor limit must be calculated using worstcase values for on- and off-times. Manufacturing tolerances and internal propagation delays introduce an error to the on-times. This error is greater at higher frequencies. Also, keep in mind that transient-response performance of buck regulators operated too close to dropout is poor, and bulk output capacitance must often be added (see the V SAG equation in the Multiphase Quick-PWM Design Procedure section. The absolute point of dropout is when the inductor current ramps down during the minimum off-time (IDOWN) as much as it ramps up during the on-time (IUP). The ratio h = IUP/IDOWN is an indicator of the ability to slew the inductor current higher in response to increased load, and must always be greater than 1. As h approaches 1, the absolute minimum dropout point, the inductor current cannot increase as much during each switching cycle and V SAG greatly increases unless additional output capacitance is used. A reasonable minimum value for h is 1.5, but adjusting this up or down allows tradeoffs between VSAG, output capacitance, and minimum operating voltage. For a given value of h, the minimum operating voltage can be calculated as: VFB - VDROOP + VDIS VIN(MIN) = TOTAL + 1 - TOTALh x tOFF(MIN)fSW VCHG - VDIS + VDROOP where TOTAL is the total number of out-of-phase switching regulators, V FB is the voltage-positioning droop, VDIS and VCHG are the parasitic voltage drops in the discharge and charge paths (see the On-Time One-Shot section), t OFF(MIN) is from the Electrical Characteristics table. The absolute minimum input voltage is calculated with h = 1. If the calculated VIN(MIN) is greater than the required minimum input voltage, then reduce the operating frequency or add output capacitance to obtain an acceptable VSAG. If operation near dropout is anticipated, calculate V SAG to be sure of adequate transient response. Dropout design example: VFB = 1.4V fSW = 300kHz tOFF(MIN) = 400ns VDROOP = 3mV/A x 30A = 90mV VDIS = VCHG = 150mV (30A Load) h = 1.5 and TOTAL = 2: 1.4V - 90mV + 150mV VIN(MIN) = 2 x + 1 - 2 x (0.4s x 1.5 x 300kHz) 150mV - 150mV + 90mV = 4.96V Calculating again with h = 1 gives the absolute limit of dropout: 1.4V - 90mV + 150mV VIN(MIN) = 2 x + 1 - 2 x (0.4s x 1.0 x 300kHz) 150mV - 150mV + 90mV = 4.07V Therefore, VIN must be greater than 4.1V, even with very large output capacitance, and a practical input voltage with reasonable output capacitance would be 5.0V.
Applications Information
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching losses and clean, stable operation. The switching power stage requires particular attention. If possible, mount all the power components on the top side of the board with their ground terminals flush against one another. Refer to the MAX17082 evaluation kit specification for a layout example and follow these guidelines for good PCB layout: * Keep the high-current paths short, especially at the ground terminals. This is essential for stable, jitterfree operation. * Connect all analog grounds to a separate solid copper plane, which connects to the GND pin of the Quick-PWM controller. This includes the VCC, FB, and GNDS bypass capacitors. * Keep the power traces and load connections short. This is essential for high efficiency. The use of thick copper PCBs (2oz vs. 1oz) can enhance full-load efficiency by 1% or more. Correctly routing PCB traces is a difficult task that must be approached in terms of fractions of centimeters, where a single m of excess trace resistance causes a measurable efficiency penalty.
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies
* Keep the high-current, gate-driver traces (DL_, DH_, LX_, and BST_) short and wide to minimize trace resistance and inductance. This is essential for high-power MOSFETs that require low-impedance gate drivers to avoid shoot-through currents. CSP_ and CSN_ connections for current limiting and voltage positioning must be made using Kelvinsense connections to guarantee the current-sense accuracy. When trade-offs in trace lengths must be made, it is preferable to allow the inductor charging path to be made longer than the discharge path. For example, it is better to allow some extra distance between the input capacitors and the high-side MOSFET than to allow distance between the inductor and the lowside MOSFET or between the inductor and the output filter capacitor. Route high-speed switching nodes away from sensitive analog areas (CCI, FB, CSP_, CSN_, etc.). 3) Group the gate-drive components (BST_ diodes and capacitors, VDD bypass capacitor) together near the controller IC. 4) Make the DC-DC controller ground connections as shown in Figures 1 and 2. This diagram can be viewed as having four separate ground planes: input/output ground, where all the high-power components go; the power ground plane, where the GND pin and VDD bypass capacitor go; the master's analog ground plane where sensitive analog components go, the master's GND pin and VCC bypass capacitor go; and the slave's analog ground plane where the slave's GND pin and VCC bypass capacitor go. The master's GND plane must meet the GND plane only at a single point directly beneath the IC. Similarly, the slave's GND plane must meet the GND plane only at a single point directly beneath the IC. The respective master and slave ground planes should connect to the highpower output ground with a short metal trace from GND to the source of the low-side MOSFET (the middle of the star ground). This point must also be very close to the output capacitor ground terminal. 5) Connect the output power planes (VCORE and system ground planes) directly to the output filter capacitor positive and negative terminals with multiple vias. Place the entire DC-DC converter circuit as close to the CPU as is practical.
MAX17021/MAX17082/MAX17482
*
*
*
Layout Procedure
1) Place the power components first, with ground terminals adjacent (low-side MOSFET source, C IN, COUT, and D1 anode). If possible, make all these connections on the top layer with wide, copperfilled areas. 2) Mount the controller IC adjacent to the low-side MOSFET. The DL_ gate traces must be short and wide (50 mils to 100 mils wide if the MOSFET is 1in from the controller IC).
Chip Information
PROCESS: BiCMOS
PACKAGE TYPE 40 TQFN-EP
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE CODE T4055-2 DOCUMENT NO. 21-0140
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Dual-Phase, Quick-PWM Controllers for IMVP-6+/IMVP-6.5 CPU Core Power Supplies MAX17021/MAX17082/MAX17482
Revision History
REVISION NUMBER 0 1 REVISION DATE 11/08 7/09 Initial release Correction to non-OVP version, update IMON equations, fix errors in Figures 1, 2, and 4 DESCRIPTION PAGES CHANGED -- 1, 2, 4, 13, 14, 16, 19, 22, 25, 33-36, 39, 40, 46, 47
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
48 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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