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LTM4602 6A High Efficiency DC/DC Module FEATURES
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DESCRIPTION
The LTM(R)4602 is a complete 6A DC/DC step down power supply. Included in the package are the switching controller, power FETs, inductor, and all support components. Operating over an input voltage range of 4.5V to 20V, the LTM4602 supports an output voltage range of 0.6V to 5V, set by a single resistor. This high efficiency design delivers 6A continuous current (8A peak), needing no heat sinks or airflow to meet power specifications. Only bulk input and output capacitors are needed to finish the design. The low profile package (2.8mm) enables utilization of unused space on the bottom of PC boards for high density point of load regulation. High switching frequency and an adaptive on-time current mode architecture enables a very fast transient response to line and load changes without sacrificing stability. Fault protection features include integrated overvoltage and short circuit protection with a defeatable shutdown timer. A built-in soft-start timer is adjustable with a small capacitor. The LTM4602 is packaged in a thermally enhanced, compact (15mm x 15mm) and low profile (2.8mm) over-molded Land Grid Array (LGA) package suitable for automated assembly by standard surface mount equipment. For the 4.5V to 28V input range version, refer to the LTM4602HV.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Module is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 6100678, 6580258, 5847554, 6304066.
Complete Switch Mode Power Supply Wide Input Voltage Range: 4.5V to 20V 6A DC, 8A Peak Output Current 0.6V to 5V Output Voltage 1.5% Output Voltage Regulation Ultrafast Transient Response Current Mode Control Pb-Free (e4) RoHS Compliant Package with GoldPad Finish Pin Compatible with the LTM4600 Up to 92% Efficiency Programmable Soft-Start Output Overvoltage Protection Optional Short-Circuit Shutdown Timer See the LTM4602HV for Operation Up to 28VIN Small Footprint, Low Profile (15mm x 15mm x 2.8mm) Surface Mount LGA Package
APPLICATIONS
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Telecom and Networking Equipment Servers Industrial Equipment Point of Load Regulation
TYPICAL APPLICATION
6A ModuleTM Power Supply with 4.5V to 20V Input
VIN 4.5V TO 20V VIN CIN VOUT LTM4602 VOSET PGND SGND COUT VOUT 1.5V 6A 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0
Efficiency vs Load Current with 12VIN (FCB = 0)
RSET 66.5k
4602 TA01a
0.8VOUT 1.2VOUT 1.5VOUT 1.8VOUT 2.5VOUT 3.3VOUT 3.3VOUT (950kHz)* *950kHz INSTEAD OF 1.3MHz INCREASES 3.3V EFFICIENCY 2% 2 4 6 LOAD CURRENT (A) 8
4602 TA01b
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LTM4602 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
fADJ SVIN EXTVCC VOSET COMP SGND RUN/SS FCB PGOOD PGND TOP VIEW
FCB, EXTVCC, PGOOD, RUN/SS, VOUT .......... -0.3V to 6V VIN, SVIN, fADJ ............................................ -0.3V to 20V VOSET, COMP ............................................. -0.3V to 2.7V Operating Temperature Range (Note 2).... -40C to 85C Junction Temperature ........................................... 125C Storage Temperature Range................... -55C to 125C
VIN
VOUT LGA PACKAGE 104-LEAD (15mm x 15mm x 2.8mm) TJMAX = 125C, JA = 15C/W, JC = 6C/W, JA DERIVED FROM 95mm x 76mm PCB WITH 4 LAYERS WEIGHT = 1.7g
ORDER INFORMATION
LEAD FREE FINISH LTM4602EV#PBF LTM4602IV#PBF PART MARKING* LTM4602V LTM4602V PACKAGE DESCRIPTION 104-Lead (15mm x 15mm x 2.8mm) LGA 104-Lead (15mm x 15mm x 2.8mm) LGA TEMPERATURE RANGE -40C to 85C -40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
The l denotes the specifications which apply over the -40C to 85C temperature range, otherwise specifications are at TA = 25C, VIN = 12V. External CIN = 120F COUT = 200F/Ceramic per typical , application (front page) configuration.
SYMBOL VIN(DC) VOUT(DC) PARAMETER Input DC Voltage Output Voltage FCB = 0V VIN = 5V or 12V, VOUT = 1.5V, IOUT = 0A CONDITIONS
l
ELECTRICAL CHARACTERISTICS
MIN 4.5 1.478 1.470
TYP
MAX 20
UNITS V V
l
1.50 1.50 3.4 0.6 0.7 1.2 42 1.0 52 50
1.522 1.530 4
Input Specifications VIN(UVLO) IINRUSH(VIN) Under Voltage Lockout Threshold Input Inrush Current at Startup IOUT = 0A IOUT = 0A. VOUT = 1.5V, FCB = 0 VIN = 5V VIN = 12V IOUT = 0A, EXTVCC Open VIN = 12V, VOUT = 1.5V, FCB = 5V VIN = 12V, VOUT = 1.5V, FCB = 0V VIN = 5V, VOUT = 1.5V, FCB = 5V VIN = 5V, VOUT = 1.5V, FCB = 0V Shutdown, RUN = 0.8V, VIN = 12V V A A mA mA mA mA A
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IQ(VIN)
Input Supply Bias Current
100
2
LTM4602 ELECTRICAL CHARACTERISTICS
SYMBOL IS(VIN) PARAMETER Input Supply Current
The l denotes the specifications which apply over the -40C to 85C temperature range, otherwise specifications are at TA = 25C, VIN = 12V. Per typical application (front page) configuration.
CONDITIONS VIN = 12V, VOUT = 1.5V, IOUT = 6A VIN = 12V, VOUT = 3.3V, IOUT = 6A VIN = 5V, VOUT = 1.5V, IOUT = 6 A 0 MIN TYP 0.88 1.80 2.08 6 MAX UNITS A A A A
Output Specifications IOUTDC Output Continuous Current Range VIN = 12V, VOUT = 1.5V (See Output Current Derating Curves for Different VIN, VOUT and TA) Line Regulation Accuracy Load Regulation Accuracy VOUT = 1.5V, IOUT = 0A, FCB = 0V, VIN = 4.5V to 20V VOUT = 1.5V, IOUT = 0A to 6A, FCB = 0V, VIN = 5V, VIN = 12V (Note 3) VIN = 12V, VOUT = 1.5V, IOUT = 0A, FCB = 0V VOUT = 1.5V, IOUT = 6A, FCB = 0V VOUT = 1.5V, IOUT = 1A VIN = 12V VIN = 5V VOUT = 1.5V, Load Step: 0A/s to 3A/s COUT = 22F 6.3V, 330F 4V POSCAP , See Table 2 Load: 10% to 50% to 10% of Full Load Output Voltage in Foldback VIN = 12V, VOUT = 1.5V VIN = 5V, VOUT = 1.5V IOUT = 0A, VOUT = 1.5V VRUN/SS = 0V VRUN/SS = 4V EXTVCC = 0V, FCB = 0V Current into EXTVCC Pin Resistor Between VOUT and VOSET Pins Forced Continuous Threshold Forced Continuous Pin Current PGOOD Upper Threshold PGOOD Lower Threshold PGOOD Hysteresis PGOOD Low Voltage VFCB = 0.6V VOSET Rising VOSET Falling VOSET Returning IPGOOD = 5mA 7.5 -7.5 0.57 EXTVCC = 5V, FCB = 0V, VOUT = 1.5V, IOUT = 0A
l l
VOUT(LINE) VOUT VOUT(LOAD) VOUT VOUT(AC) fs tSTART
0.15
0.3
%
l
0.25 0.15 10 850 0.5 0.7 30
0.5 1.0 15
% % mVP-P kHz ms ms mV
Output Ripple Voltage Output Ripple Voltage Frequency Turn-On Time
VOUTLS
Voltage Drop for Dynamic Load Step
tSETTLE IOUTPK
Settling Time for Dynamic Load Step Output Current Limit
25 9 9 0.591 0.8 -0.5 0.8 0.6 1.5 -1.2 1.8 100 16 100 0.6 -1 10 -10 2 0.15 0.4 0.63 -2 12.5 -12.5 0.609 2 -3 3
s A A V V A A mV mA k V A % % % V
Control Stage VOSET VRUN/SS IRUN(C)/SS IRUN(D)/SS VIN - SVIN IEXTVCC RFBHI VFCB IFCB PGOOD Output VOSETH VOSETL VOSET(HYS) VPGL Voltage at VOSET Pin RUN ON/OFF Threshold Soft-Start Charging Current Soft-Start Discharging Current
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime.
Note 2: The LTM4602E is guaranteed to meet performance specifications from 0C to 85C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LTM4602I is guaranteed over the -40C to 85C temperature range. Note 3: Test assumes current derating versus temperature.
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LTM4602 TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current with 5VIN (FCB = 0)
100 90 80 EFFICIENCY (%) 70 60 50 40 30 EFFICIENCY (%) 0.8VOUT 1.2VOUT 1.5VOUT 1.8VOUT 2.5VOUT 3.3VOUT* *FOR 5V TO 3.3V CONVERSION, SEE FREQUENCY ADJUSTMENT IN APPLICATIONS INFORMATION 0 2 4 6 LOAD CURRENT (A) 8
4602 G01
(See Figure 21 for all curves) Efficiency vs Load Current with 20VIN (FCB = 0)
100 90 80 70 60 50 40 30 1.2VOUT 1.5VOUT 1.8VOUT 2.5VOUT 3.3VOUT 0 2 4 LOAD CURRENT (A)
4602 G02 4602 G03
Efficiency vs Load Current with 12VIN (FCB = 0)
100 90 80 70 60 50 40 30 0 2 0.8VOUT 1.2VOUT 1.5VOUT 1.8VOUT 2.5VOUT 3.3VOUT 3.3VOUT (950kHz)* *950kHz INSTEAD OF 1.3MHz INCREASES 3.3V EFFICIENCY 2% 4 6 LOAD CURRENT (A) 8 EFFICIENCY (%)
6
8
Light Load Efficiency vs Load Current with 12VIN (FCB > 0.7V, <5V)
100 90 80 EFFICIENCY (%) 70 60 50 40 30 1.2VOUT 1.5VOUT 1.8VOUT 2.5VOUT 3.3VOUT 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 LOAD CURRENT (A) 1 VOUT 50mV/DIV IOUT 2A/DIV
1.2V Transient Response
1.5V Transient Response
VOUT 50mV/DIV IOUT 2A/DIV 20s/DIV 1.2V AT 3A/s LOAD STEP COUT = 1 x 22F, 6.3V CERAMICS 330F, 4V SANYO POSCAP
4602 G05
20s/DIV 1.5V AT 3A/s LOAD STEP COUT = 1 x 22F, 6.3V CERAMICS 330F, 4V SANYO POSCAP
4602 G06
4602 G04
1.8V Transient Response
VOUT 50mV/DIV VOUT 50mV/DIV
2.5V Transient Response
VOUT 50mV/DIV
3.3V Transient Response
IOUT 2A/DIV 20s/DIV 1.8V AT 3A/s LOAD STEP COUT = 1 x 22F, 6.3V CERAMICS 330F, 4V SANYO POSCAP
4602 G07
IOUT 2A/DIV 20s/DIV 2.5V AT 3A/s LOAD STEP COUT = 1 x 22F, 6.3V CERAMICS 330F, 4V SANYO POSCAP
4602 G08
IOUT 2A/DIV 20s/DIV 3.3V AT 3A/s LOAD STEP COUT = 1 x 22F, 6.3V CERAMICS 330F, 4V SANYO POSCAP
4602 G09
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LTM4602 TYPICAL PERFORMANCE CHARACTERISTICS (See Figure 21 for all curves)
Start-Up, No Load, IOUT = 0A Start-Up, IOUT = 6A (Resistive Load) Short-Circuit Protection, IOUT = 0A
VOUT 0.5V/DIV
VOUT 0.5V/DIV
VOUT 0.5V/DIV
IIN 0.5A/DIV 200s/DIV VIN = 12V VOUT = 1.5V COUT = 1 x 22F, 6.3V X5R 330F, 4V SANYO POSCAP NO EXTERNAL SOFT-START CAPACITOR
4602 G10
IIN 0.5A/DIV 500s/DIV VIN = 12V VOUT = 1.5V COUT = 1 x 22F, 6.3V X5R 330F, 4V SANYO POSCAP NO EXTERNAL SOFT-START CAPACITOR
4602 G11
IIN 0.5A/DIV 20s/DIV VIN = 12V VOUT = 1.5V COUT = 1 x 22F, 6.3V X5R 330F, 4V SANYO POSCAP NO EXTERNAL SOFT-START CAPACITOR
4602 G12
Short-Circuit Protection, IOUT = 6A
5.5 5.0 VOUT 0.5V/DIV VOUT (V) 4.5 4.0 3.5 IIN 0.5A/DIV 20s/DIV VIN = 12V VOUT = 1.5V COUT = 1 x 22F, 6.3V X5R 330F, 4V SANYO POSCAP NO EXTERNAL SOFT-START CAPACITOR
4602 G13
VIN to VOUT Step-Down Ratio
fADJ = OPEN 5V
3.3V 2.5V 1.8V 1.5V 1.2V 0.6V 0 5 10 VIN (V) SEE FREQUENCY ADJUSTMENT DISCUSSION FOR 12VIN TO 5VOUT AND 5VIN TO 3.3VOUT CONVERSION
4602 G14
3.0 2.5 2.0 1.5 1.0 0.5 0
15
20
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LTM4602 PIN FUNCTIONS
(See Package Description for Pin Assignment)
VIN (Bank 1): Power Input Pins. Apply input voltage between these pins and PGND pins. Recommend placing input decoupling capacitance directly between VIN pins and PGND pins. fADJ (Pin A15): A 110k resistor from VIN to this pin sets the one-shot timer current, thereby setting the switching frequency. The LTM4602 switching frequency is typically 850kHz. An external resistor to ground can be selected to reduce the one-shot timer current, thus lower the switching frequency to accommodate a higher duty cycle step down requirement. See the applications section. SVIN (Pin A17): Supply Pin for Internal PWM Controller. Leave this pin open or add additional decoupling capacitance. EXTVCC (Pin A19): External 5V supply pin for controller. If left open or grounded, the internal 5V linear regulator will power the controller and MOSFET drivers. For high input voltage applications, connecting this pin to an external 5V will reduce the power loss in the power module. The EXTVCC voltage should never be higher than VIN. VOSET (Pin A21): The Negative Input of The Error Amplifier. Internally, this pin is connected to VOUT with a 100k precision resistor. Different output voltages can be programmed with additional resistors between the VOSET and SGND pins. COMP (Pin B23): Current Control Threshold and Error Amplifier Compensation Point. The current comparator threshold increases with this control voltage. The voltage ranges from 0V to 2.4V with 0.8V corresponding to zero sense voltage (zero current).
SGND (Pin D23): Signal Ground Pin. All small-signal components should connect to this ground, which in turn connects to PGND at one point. RUN/SS (Pin F23): Run and Soft-Start Control. Forcing this pin below 0.8V will shut down the power supply. Inside the power module, there is a 1000pF capacitor which provides approximately 0.7ms soft-start time with 200F output capacitance. Additional soft-start time can be achieved by adding additional capacitance between the RUN/SS and SGND pins. The internal short-circuit latchoff can be disabled by adding a resistor between this pin and the VIN pin. This pullup resistor must supply a minimum 5A pull up current. FCB (Pin G23): Forced Continuous Input. Grounding this pin enables forced continuous mode operation regardless of load conditions. Tying this pin above 0.63V enables discontinuous conduction mode to achieve high efficiency operation at light loads. There is an internal 4.75k resistor between the FCB and SGND pins. PGOOD (Pin J23): Output Voltage Power Good Indicator. When the output voltage is within 10% of the nominal voltage, the PGOOD is open drain output. Otherwise, this pin is pulled to ground. PGND (Bank 2): Power ground pins for both input and output returns. VOUT (Bank 3): Power Output Pins. Apply output load between these pins and PGND pins. Recommend placing High Frequency output decoupling capacitance directly between these pins and PGND pins.
EXTVCC
81
TOP VIEW SVIN fADJ
VOSET
91
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
21 22
6
401
39
301
29
201
19
101
09
001
98
88
99
78
89
68
79
58
69
48
59
49
38
VOUT BANK 3
94
06
17
28
84
95
07
18
85
96
08
74
75
86
97
64
65
76
87
54
55
66
77
44
45
56
67
34
35
46
57
24
25
36
47
14
04
15
26
37
93
PGND BANK 2
23
4602 PN01
12
22
32
42
13
83
73
03
51
92
63
41
82
53
31
43
72
62
33
05
16
27
23
21
52
8
VIN BANK 1
02 11 01 9
71
61
7
6
5
4
3
2 1
A B C D E F G H J K
COMP SGND RUN/SS FCB PGOOD
L M N
P R T
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LTM4602 SIMPLIFIED BLOCK DIAGRAM
SVIN RUN/SS 1000pF PGOOD Q1 COMP FCB COUT 4.75k fADJ SGND EXTVCC VOSET RSET 66.5k 100k 0.5% 10 CONTROLLER Q2 15F 6.3V PGND INT COMP VOUT 1.5V 6A MAX 1.5F CIN VIN 4.5V TO 20V
4602 F01
Figure 1. Simplified LTM4602 Block Diagram
DECOUPLING REQUIREMENTS TA = 25C, VIN = 12V. Use Figure 1 configuration.
SYMBOL CIN COUT PARAMETER External Input Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 1.5V) External Output Capacitor Requirement (VIN = 4.5V to 20V, VOUT = 1.5V) CONDITIONS IOUT = 6A IOUT = 6A, Refer to Table 2 in the Applications Information Section MIN 20 100 200 TYP MAX UNITS F F
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LTM4602 OPERATION
Module Description The LTM4602 is a standalone nonisolated synchronous switching DC/DC power supply. It can deliver up to 6A of DC output current with only bulk external input and output capacitors. This module provides a precisely regulated output voltage programmable via one external resistor from 0.6VDC to 5.0VDC, not to exceed 80% of the input voltage. The input voltage range is 4.5V to 20V. A simplified block diagram is shown in Figure 1 and the typical application schematic is shown in Figure 21. The LTM4602 contains an integrated LTC constant on-time current-mode regulator, ultralow RDS(ON) FETs with fast switching speed and integrated Schottky diode. The typical switching frequency is 850kHz at full load. With current mode control and internal feedback loop compensation, the LTM4602 module has sufficient stability margins and good transient performance under a wide range of operating conditions and with a wide range of output capacitors, even all ceramic output capacitors (X5R or X7R). Current mode control provides cycle-by-cycle fast current limit. In addition, foldback current limiting is provided in an overcurrent condition while VOSET drops. Also, the LTM4602 has defeatable short-circuit latch off. Internal overvoltage and undervoltage comparators pull the opendrain PGOOD output low if the output feedback voltage exits a 10% window around the regulation point. Furthermore, in an overvoltage condition, internal top FET Q1 is turned off and bottom FET Q2 is turned on and held on until the overvoltage condition clears. Pulling the RUN/SS pin low forces the controller into its shutdown state, turning off both Q1 and Q2. Releasing the pin allows an internal 1.2A current source to charge up the soft-start capacitor. When this voltage reaches 1.5V, the controller turns on and begins switching. At low load current the module works in continuous current mode by default to achieve minimum output voltage ripple. It can be programmed to operate in discontinuous current mode for improved light load efficiency when the FCB pin is pulled up above 0.8V and no higher than 6V. The FCB pin has a 4.75k resistor to ground, so a resistor to VIN can set the voltage on the FCB pin. When EXTVCC pin is grounded or open, an integrated 5V linear regulator powers the controller and MOSFET gate drivers. If a minimum 4.7V external bias supply is applied on the EXTVCC pin, the internal regulator is turned off, and an internal switch connects EXTVCC to the gate driver voltage. This eliminates the linear regulator power loss with high input voltage, reducing the thermal stress on the controller. The maximum voltage on EXTVCC pin is 6V. The EXTVCC voltage should never be higher than the VIN voltage. Also EXTVCC must be sequenced after VIN.
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LTM4602 APPLICATIONS INFORMATION
The typical LTM4602 application circuit is shown in Figure 21. External component selection is primarily determined by the maximum load current and output voltage. Output Voltage Programming and Margining The PWM controller of the LTM4602 has an internal 0.6V reference voltage. As shown in the block diagram, a 100k/0.5% internal feedback resistor connects VOUT and VOSET pins. Adding a resistor RSET from VOSET pin to SGND pin programs the output voltage: VOUT = 0.6V * 100k + RSET RSET voltage VOUT needs to be margined up/down by M%, the resistor values of RUP and RDOWN can be calculated from the following equations: (RSET RUP ) * VOUT * (1+ M%) (RSET RUP ) + 100k = 0.6V
RSET * VOUT * (1- M%) = 0.6V RSET + (100k RDOWN ) Input Capacitors The LTM4602 Module should be connected to a low AC-impedance DC source. High frequency, low ESR input capacitors are required to be placed adjacent to the module. In Figure 21, the bulk input capacitor CIN is selected for its ability to handle the large RMS current into the converter. For a buck converter, the switching duty cycle can be estimated as: D= VOUT VIN
Table 1 shows the standard values of 1% RSET resistor for typical output voltages:
Table 1
RSET (k) VOUT (V) Open 0.6 100 1.2 66.5 1.5 49.9 1.8 43.2 2 31.6 2.5 22.1 3.3 13.7 5
Voltage margining is the dynamic adjustment of the output voltage to its worst case operating range in production testing to stress the load circuitry, verify control/protection functionality of the board and improve the system reliability. Figure 2 shows how to implement margining function with the LTM4602. In addition to the feedback resistor RSET, several external components are added. Turn off both transistor QUP and QDOWN to disable the margining. When QUP is on and QDOWN is off, the output voltage is margined up. The output voltage is margined down when QDOWN is on and QUP is off. If the output
LTM4602 VOUT RDOWN 100k QDOWN VOSET PGND SGND RSET 2N7002 RUP
Without considering the inductor current ripple, the RMS current of the input capacitor can be estimated as: ICIN(RMS) = IOUT(MAX) % * D * (1 D)
In the above equation, % is the estimated efficiency of the power module. C1 can be a switcher-rated electrolytic aluminum capacitor, OS-CON capacitor or high volume ceramic capacitors. Note the capacitor ripple current ratings are often based on only 2000 hours of life. This makes it advisable to properly derate the input capacitor, or choose a capacitor rated at a higher temperature than required. Always contact the capacitor manufacturer for derating requirements. In Figure 21, the input capacitors are used as high frequency input decoupling capacitors. In a typical 6A output application, 1-2 pieces of very low ESR X5R or X7R, 10F ceramic capacitors are recommended. This decoupling capacitor should be placed directly adjacent the module input pins in the PCB layout to minimize the trace inductance and high frequency AC noise.
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QUP 2N7002
4602 F02
Figure 2. LTM4602 Margining Implementation
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LTM4602 APPLICATIONS INFORMATION
Output Capacitors The LTM4602 is designed for low output voltage ripple. The bulk output capacitors COUT is chosen with low enough effective series resistance (ESR) to meet the output voltage ripple and transient requirements. COUT can be low ESR tantalum capacitor, low ESR polymer capacitor or ceramic capacitor (X5R or X7R). The typical capacitance is 200F if all ceramic output capacitors are used. The internally optimized loop compensation provides sufficient stability margin for all ceramic capacitors applications. Additional output filtering may be required by the system designer, if further reduction of output ripple or dynamic transient spike is required. Refer to Table 2 for an output capacitance matrix for each output voltage droop, peak to peak deviation and recovery time during a 3A/s transient with a specific output capacitance. Fault Conditions: Current Limit and Overcurrent Foldback The LTM4602 has a current mode controller, which inherently limits the cycle-by-cycle inductor current not only in steady-state operation, but also in transient. To further limit current in the event of an over load condition, the LTM4602 provides foldback current limiting. If the output voltage falls by more than 50%, then the maximum output current is progressively lowered to about one sixth of its full current limit value. Soft-Start and Latchoff with the RUN/SS pin The RUN/SS pin provides a means to shut down the LTM4602 as well as a timer for soft-start and overcurrent latchoff. Pulling the RUN/SS pin below 0.8V puts the LTM4602 into a low quiescent current shutdown (IQ 100A). Releasing the pin allows an internal 1.2A current source to charge up the timing capacitor CSS. Inside LTM4602, there is an internal 1000pF capacitor from RUN/ SS pin to ground. If RUN/SS pin has an external capacitor CSS_EXT to ground, the delay before starting is about: tDELAY = 1.5V * (CSS_EXT + 1000pF) 1.2A
When the voltage on RUN/SS pin reaches 1.5V, the LTM4602 internal switches are operating with a clamping of the maximum output inductor current limited by the RUN/SS pin total soft-start capacitance. As the RUN/SS pin voltage rises to 3V, the soft-start clamping of the inductor current is released. VIN to VOUT Step-Down Ratios There are restrictions in the maximum VIN to VOUT step down ratio that can be achieved for a given input voltage. These constraints are shown in the Typical Performance Characteristics curves labeled "VIN to VOUT Step-Down Ratio". Note that additional thermal derating may apply. See the Thermal Considerations and Output Current Derating sections of this data sheet.
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LTM4602 APPLICATIONS INFORMATION
Table 2. Output Voltage Response Versus Component Matrix (Refer to Figure 21), 0A to 3A Step (Typical Values)
TYPICAL MEASURED VALUES COUT1 VENDORS TDK TAIYO YUDEN TAIYO YUDEN VOUT (V) 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 5 5 CIN (CERAMIC) 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V 2 x 10F 25V PART NUMBER C4532X5R0J107MZ (100F ,6.3V) JMK432BJ107MU-T ( 100F 6.3V) , JMK316BJ226ML-T501 ( 22F 6.3V) , COUT1 (CERAMIC) 3 x 22F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 3 x 22F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 3 x 22F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 3 x 22F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 3 x 22F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 3 x 22F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 1 x 100F 6.3V 2 x 100F 6.3V 3 x 22F 6.3V 4 x 100F 6.3V 1 x 100F 6.3V 3 x 22F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 2 x 100F 6.3V 1 x 100F 6.3V 3 x 22F 6.3V 4 x 100F 6.3V 1 x 100F 6.3V 3 x 22F 6.3V 2 x 100F 6.3V 4 x 100F 6.3V 1 x 100F 6.3V 1 x 100F 6.3V COUT2 (BULK) 470F 4V 470F 2.5V 330F 6.3V NONE 470F 4V 470F 2.5V 330F 6.3V NONE 470F 4V 470F 2.5V 330F 6.3V NONE 470F 4V 470F 2.5V 330F 6.3V NONE 470F 4V 470F 2.5V 330F 6.3V NONE 470F 4V 470F 2.5V 330F 6.3V NONE 470F 4V 330F 6.3V 470F 4V NONE 470F 4V 470F 4V 330F 6.3V NONE 330F 6.3V 470F 4V 470F 4V NONE 470F 4V 470F 4V 330F 6.3V NONE NONE NONE CCOMP NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE NONE COUT2 VENDORS SANYO POSCAP SANYO POSCAP SANYO POSCAP C3 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 100pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 220pF 100pF 100pF VIN (V) 5 5 5 5 12 12 12 12 5 5 5 5 12 12 12 12 5 5 5 5 12 12 12 12 5 5 5 5 12 12 12 12 7 7 7 7 12 12 12 12 15 20 DROOP (mV) 50 30 25 25 30 25 25 25 25 25 28 26 25 25 28 26 25 25 25 29 25 25 25 29 25 25 25 25 25 25 25 27 32 30 30 32 38 30 30 32 80 80 PART NUMBER 6TPE330MIL (330F 6.3V) , 2R5TPE470M9 (470F 2.5V) , 4TPE470MCL (470F 4V) , PEAK TO PEAK (mV) 60 60 54 55 60 54 50 55 50 54 59 59 55 54 59 59 54 50 50 60 50 50 50 60 50 50 50 50 50 50 50 54 64 60 60 64 58 60 60 64 160 160 RECOVERY TIME (s) 25 20 20 20 25 20 20 20 25 20 20 20 25 20 20 20 30 20 20 20 30 20 20 20 30 30 30 25 30 30 30 25 30 30 35 25 30 35 30 25 25 25 LOAD STEP (A/s) 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3
CIN (BULK) 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V 150F 35V
4602fa
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LTM4602 APPLICATIONS INFORMATION
After the controller has been started and given adequate time to charge up the output capacitor, CSS is used as a short-circuit timer. After the RUN/SS pin charges above 4V, if the output voltage falls below 75% of its regulated value, then a short-circuit fault is assumed. A 1.8A current then begins discharging CSS. If the fault condition persists until the RUN/SS pin drops to 3.5V, then the controller turns off both power MOSFETs, shutting down the converter permanently. The RUN/SS pin must be actively pulled down to ground in order to restart operation. The overcurrent protection timer requires the soft-start timing capacitor CSS be made large enough to guarantee that the output regulation by the time CSS has reached the 4V threshold. In general, this will depend upon the size of the output capacitance, output voltage and load current characteristic. A minimum external soft-start capacitor can be estimated from: CSS_EXT + 1000pF > COUT * VOUT (10 -3[F / VS ]) Generally 0.1F is more than sufficient. Since the load current is already limited by the current mode control and current foldback circuitry during a short circuit, overcurrent latchoff operation is NOT always needed or desired, especially if the output has large capacitance or the load draws high current during start up. The latchoff feature can be overridden by a pull-up current greater than 5A but less than 80A to the RUN/SS pin. The additional current prevents the discharge of CSS during a fault and also shortens the soft-start period. Using a resistor from RUN/SS pin to VIN is a simple solution to defeat latchoff. Any pull-up network must be able to maintain RUN/SS above 4V maximum latchoff threshold and overcome the 4A maximum discharge current. Figure 3 shows a conceptual drawing of VRUN during start-up and short circuit.
VRUN/SS 4V 3.5V 3V 1.5V
SHORT-CIRCUIT LATCH ARMED t SOFT-START CLAMPING OF IL RELEASED VOUT 75%VO OUTPUT OVERLOAD HAPPENS SHORT-CIRCUIT LATCHOFF
SWITCHING STARTS
t
4602 F03
Figure 3. RUN/SS Pin Voltage During Startup and Short-Circuit Protection
VIN RRUN/SS VIN LTM4602 RUN/SS PGND SGND
RECOMMENDED VALUES FOR RRUN/SS VIN 4.5V TO 5.5V 10.8V TO 13.8V 16V TO 20V RRUN/SS 50k 150k 330k
4602 F04
Figure 4. Defeat Short-Circuit Latchoff with a Pull-Up Resistor to VIN
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LTM4602 APPLICATIONS INFORMATION
Enable The RUN/SS pin can be driven from logic as shown in Figure 5. This function allows the LTM4602 to be turned on or off remotely. The ON signal can also control the sequence of the output voltage.
RUN/SS ON LTM4602 PGND SGND 2N7002
4602 F05
EXTVCC Connection An internal low dropout regulator produces an internal 5V supply that powers the control circuitry and FET drivers. Therefore, if the system does not have a 5V power rail, the LTM4602 can be directly powered by VIN. The gate driver current through LDO is about 18mA. The internal LDO power dissipation can be calculated as: PLDO_LOSS = 18mA * (VIN - 5V) The LTM4602 also provides an external gate driver voltage pin EXTVCC. If there is a 5V rail in the system, it is recommended to connect EXTVCC pin to the external 5V rail. Whenever the EXTVCC pin is above 4.7V, the internal 5V LDO is shut off and an internal 50mA P-channel switch connects the EXTVCC to internal 5V. Internal 5V is supplied from EXTVCC until this pin drops below 4.5V. Do not apply more than 6V to the EXTVCC pin and ensure that EXTVCC < VIN. The following list summaries the possible connections for EXTVCC: 1. EXTVCC grounded. Internal 5V LDO is always powered from the internal 5V regulator. 2. EXTVCC connected to an external supply. Internal LDO is shut off. A high efficiency supply compatible with the MOSFET gate drive requirements (typically 5V) can improve overall efficiency. With this connection, it is always required that the EXTVCC voltage can not be higher than VIN pin voltage. Discontinuous Operation and FCB Pin
1.8V
Figure 5. Enable Circuit with External Logic
Output Voltage Tracking For the applications that require output voltage tracking, several LTM4602 modules can be programmed by the power supply tracking controller such as the LTC2923. Figure 6 shows a typical schematic with LTC2923. Coincident, ratiometric and offset tracking for VOUT rising and falling can be implemented with different sets of resistor values. See the LTC2923 data sheet for more details.
VIN 5V Q1 DC/DC 3.3V
VIN VIN RONB RONA VCC ON LTC2923 RAMPBUF RTB1 TRACK1 RTA1 RTB2 TRACK2 RTA2 GND FB2 RSET 66.5k
4602 F06
GATE
RAMP FB1 RSET 49.9k
LTM4602 VOSET VOUT
STATUS SDO
VIN VIN LTM4602 VOSET VOUT 1.5V
The FCB pin determines whether the internal bottom MOSFET remains on when the inductor current reverses. There is an internal 4.75k pull-down resistor connecting this pin to ground. The default light load operation mode is forced continuous (PWM) current mode. This mode provides minimum output voltage ripple. In the application where the light load efficiency is important, tying the FCB pin above 0.6V threshold enables discontinuous operation where the bottom MOSFET turns off when inductor current reverses. Therefore, the conduc-
Figure 6. Output Voltage Tracking with the LTC2923 Controller
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LTM4602 APPLICATIONS INFORMATION
tion loss is minimized and light load efficiency is improved. The penalty is that the controller may skip cycle and the output voltage ripple increases at light load. Paralleling Operation with Load Sharing Two or more LTM4602 modules can be paralleled to provide higher than 6A output current. Figure 7 shows the necessary interconnection between two paralleled modules. The OPTI-LOOP(R) current mode control ensures good current sharing among modules to balance the thermal stress. The new feedback equation for two or more LTM4602s in parallel is: 100k + RSET N VOUT = 0.6V * RSET where N is the number of LTM4602s in parallel. Thermal Considerations and Output Current Derating The power loss curves in Figures 8 and 13 can be used in coordination with the load current derating curves in Figures 9 to 12, and Figures 14 to 15 for calculating an approximate JA for the module with various heat
sinking methods. Thermal models are derived from several temperature measurements at the bench, and thermal modeling analysis. Application Note 103 provides a detailed explanation of the analysis for the thermal models, and the derating curves. Tables 3 and 4 provide a summary of the equivalent JA for the noted conditions. These equivalent JA parameters are correlated to the measured values, and improve with air-flow. The case temperature is maintained at 100C or below for the derating curves. This allows for 4W maximum power dissipation in the total module with top and bottom heat sinking, and 2W power dissipation through the top of the module with an approximate JC between 6C/W to 9C/W. This equates to a total of 124C at the junction of the device. The JA values in Tables 3 and 4 can be used to derive the derating curves for other output voltages. Safety Considerations The LTM4602 modules do not provide isolation from VIN to VOUT. There is no internal fuse. If required, a slow blow fuse with a rating twice the maximum input current should be provided to protect each unit from catastrophic failure.
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
VPULLUP 100k
PGOOD VIN VIN LTM4602 VOUT VOUT 12A MAX
PGND COMP VOSET SGND RSET
PGOOD COMP VOSET SGND VIN PGND LTM4602 VOUT
4602 F07
Figure 7. Parallel Two Modules with Load Sharing
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LTM4602 APPLICATIONS INFORMATION
2.0 1.8 1.6 POWER LOSS (W) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0.6 1.0 3.1 4.1 2.1 CURRENT (A) 5.1 6.1
4602 F08
7 6 5 CURRENT (A) CURRENT (A) 12V TO 1.5V LOSS 4 3 2 1 0 50 60 70 80 TEMPERATURE (C)
4602 F09
7 6 5 4 3 2 0LFM 200LFM 400LFM 90 100 1 0 50 60 70 80 TEMPERATURE (C)
4602 F10
5V TO 1.5V LOSS
0LFM 200LFM 400LFM 90 100
Figure 8. 1.5V Power Loss vs Load Current
7 6 5 CURRENT (A) 4 3 2 1 0 50 60 70 80 TEMPERATURE (C)
4602 F11
Figure 9. 5V to 1.5V, No Heat Sink
7 6 POWER LOSS (W) 5 CURRENT (A) 4 3 2
Figure 10. 5V to 1.5V, BGA Heat Sink
4.0 3.5 3.0 2.5 2.0 1.5 1.0
5V TO 3.3V LOSS 12V TO 3.3V LOSS 12V TO 3.3V (950kHz) LOSS
0LFM 200LFM 400LFM 90 100
1 0 50 60 70 80 TEMPERATURE (C)
0LFM 200LFM 400LFM 90 100
4602 F09
0.5 0 0.5 1.0 2.1 4.1 3.1 CURRENT (A) 5.1 6.1
4601 F13
Figure 11. 12V to 1.5V, No Heat Sink
Figure 12. 12v to 1.5V, BGA Heat Sink
Figure 13. 3.3V Power Loss vs Load Current
7 6 5 CURRENT (A) 4 3 2 1 0 50 60 70 80 TEMPERATURE (C)
4602 F14
7 6 5 CURRENT (A) 0LFM 200LFM 400LFM 90 100 4 3 2 1 0 50 60 70 80 TEMPERATURE (C)
4602 F15
0LFM 200LFM 400LFM 90 100
Figure 14. 5V to 3.3V, No Heat Sink
Figure 15. 5V to 3.3V, BGA Heat Sink
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LTM4602 APPLICATIONS INFORMATION
7 6 5 CURRENT (A) 4 3 2 1 0 50 0LFM 200LFM 400LFM 60 70 80 90 100
4602 F16
7 6 5 CURRENT (A) 4 3 2 1 0 50 0LFM 200LFM 400LFM 60 70 80 90 100
4602 F16
TEMPERATURE (C)
TEMPERATURE (C)
Figure 16. 12V to 3.3V, No Heat Sink
Table 3. 1.5V Output AIR FLOW (LFM) 0 200 400 0 200 400 HEAT SINK None None None BGA Heat Sink BGA Heat Sink BGA Heat Sink JA (C/W) 15.2 14 12 13.9 11.3 10.25
Figure 17. 12V to 3.3V, BGA Heat Sink
Table 4. 3.3V Output AIR FLOW (LFM) 0 200 400 0 200 400 HEAT SINK None None None BGA Heat Sink BGA Heat Sink BGA Heat Sink JA (C/W) 15.2 14.6 13.4 13.9 11.1 10.5
Layout Checklist/Example The high integration of the LTM4602 makes the PCB board layout very simple and easy. However, to optimize its electrical and thermal performance, some layout considerations are still necessary. * Use large PCB copper areas for high current path, including VIN, PGND and VOUT. It helps to minimize the PCB conduction loss and thermal stress. * Place high frequency ceramic input and output capacitors next to the VIN, PGND and VOUT pins to minimize high frequency noise. * Place a dedicated power ground layer underneath the unit. * To minimize the via conduction loss and reduce module thermal stress, use multiple vias for interconnection between top layer and other power layers. * Do not put vias directly on pads unless they are capped.
* Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND to PGND underneath the unit. Figure 18 gives a good example of the recommended layout. LTM4602 Frequency Adjustment The LTM4602 is designed to typically operate at 850kHz across most input and output conditions. The control architecture is constant on time valley mode current control. The fADJ pin is typically left open or decoupled with an optional 1000pF capacitor. The switching frequency has been optimized to maintain constant output ripple over the operating conditions. The equations for setting the operating frequency are set around a programmable constant on time. This on time is developed by a programmable current into an on board 10pF capacitor that establishes a ramp that is compared to a voltage threshold equal to the output voltage up to a 2.4V clamp. This ION current is equal to: ION = (VIN - 0.7V)/110k, with the 110k onboard resistor
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LTM4602 APPLICATIONS INFORMATION
VIN
CIN
PGND
VOUT
4600 F16
LOAD TOP LAYER
Figure 18. Recommended PCB Layout
to ~1.2MHz for 3.3V, and ~1.7MHz for 5V outputs due to Frequency = (DC/tON) When the switching frequency increases to 1.2MHz, then the time period tS is reduced to ~833 nanoseconds and at 1.7MHz the switching period reduces to ~588 nanoseconds. When higher duty cycle conversions like 5V to 3.3V and 12V to 5V need to be accommodated, then the switching frequency can be lowered to alleviate the violation of the 400ns minimum off time. Since the total switching period is tS = tON + tOFF, tOFF will be below the 400ns minimum off time. A resistor from the fADJ pin to ground can shunt current away from the on time generator, thus allowing for a longer on time and a lower switching frequency. 12V to 5V and 5V to 3.3V derivations are explained in the data sheet to lower switching frequency and accommodate these step-down conversions. Equations for setting frequency for 12V to 5V: ION = (VIN - 0.7V)/110k; ION = 103A frequency = (ION/[2.4V * 10pF]) * DC = 1.79MHz; DC = duty cycle, duty cycle is (VOUT/VIN) tS = tON + tOFF, tON = on-time, tOFF = off-time of the switching period; tS = 1/frequency tOFF must be greater than 400ns, or tS - tON > 400ns. tON = DC * tS 1MHz frequency or 1s period is chosen for 12V to 5V. tON = 0.41 * 1s 410ns tOFF = 1s - 410ns 590ns tON and tOFF are above the minimums with adequate guard band. Using the frequency = (ION/[2.4V * 10pF]) * DC, solve for ION = (1MHz * 2.4V * 10pF) * (1/0.41) 58A. ION current calculated from 12V input was 103A, so a resistor from fADJ to ground = (0.7V/15k) = 46A. 103A - 46A = 57A, sets the adequate ION current for proper frequency range for the higher duty cycle conversion of 12V to 5V. Input voltage range is limited to 9V to 16V. Higher input voltages can be used without the 15k on fADJ. The inductor ripple current gets too high above 16V, and the 400ns minimum off-time is limited below 9V.
4602fa
from VIN to fADJ. The on time is equal to tON = (VOUT/ION) * 10pF and tOFF = ts - tON. The frequency is equal to: Freq. = DC/tON. The ION current is proportional to VIN, and the regulator duty cycle is inversely proportional to VIN, therefore the step-down regulator will remain relatively constant frequency as the duty cycle adjustment takes place with lowering VIN. The on time is proportional to VOUT up to a 2.4V clamp. This will hold frequency relatively constant with different output voltages up to 2.4V. The regulator switching period is comprised of the on time and off time as depicted in Figure 19.
t (DC) DUTY CYCLE = ON ts t V DC = ON = OUT ts VIN DC FREQ = tON
4602 F19
tOFF
tON
PERIOD ts
Figure 19. LTM4602 Switching Period
The LTM4602 has a minimum (tON) on time of 100 nanoseconds and a minimum (tOFF) off time of 400 nanoseconds. The 2.4V clamp on the ramp threshold as a function of VOUT will cause the switching frequency to increase by the ratio of VOUT/2.4V for 3.3V and 5V outputs. This is due to the fact the on time will not increase as VOUT increases past 2.4V. Therefore, if the nominal switching frequency is 850kHz, then the switching frequency will increase
17
LTM4602 APPLICATIONS INFORMATION
Equations for setting frequency for 5V to 3.3V: ION = (VIN - 0.7V)/110k; ION = 39A frequency = (ION/[2.4V * 10pF]) * DC = 1.07MHz; DC = duty cycle, duty cycle is (VOUT/VIN) tS = tON + tOFF, tON = on-time, tOFF = off-time of the switching period; tS = 1/frequency tOFF must be greater than 400ns, or tS - tON > 400ns. tON = DC * tS ~450kHz frequency or 2.22s period is chosen for 5V to 3.3V. Frequency range is about 450kHz to 650kHz from 4.5V to 7V input. tON = 0.66 * 2.22s 1.46s tOFF = 2.22s - 1.46s 760ns tON and tOFF are above the minimums with adequate guard band. Using the frequency = (ION/[2.4V * 10pF]) * DC, solve for ION = (450kHz * 2.4V * 10pF) * (1/0.66) 16A. ION current calculated from 5V input was 39A, so a resistor from fADJ to ground = (0.7V/30.1k) = 23A. 39A - 23A = 16A, sets the adequate ION current for proper frequency range for the higher duty cycle conversion of 5V to 3.3V. Input voltage range is limited to 4.5V to 7V. Higher input voltages can be used without the 30.1k on fADJ. The inductor ripple current gets too high above 7V, and the 400ns minimum off-time is limited below 4.5V. In 12V to 3.3V applications, if a 35k resistor is added from the fADJ pin to ground, then a 2% efficiency gain will be achieved as shown in the 12V efficiency graph in the Typical Performance Characteristics. This is due to the lower transition losses in the power MOSFETs after lowering the switching frequency down from 1.3MHz to 950kHz.
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LTM4602 APPLICATIONS INFORMATION
5V to 3.3V at 5A
VIN 4.5V TO 7V C3 10F 25V C1 10F 25V EXTVCC FCB LTM4602 RUN/SOFT-START RUN/SS COMP SGND SVIN PGOOD PGND
4602 F20a
R1 30.1k C5 100pF VOUT VOSET RSET 22.1k 1% OPEN DRAIN C2 22F
VIN
fADJ
VOUT 3.3V AT 5A
EFFICIENCY = 94% AT 5A LOAD
+
C4 330F 6.3V
5V TO 3.3V AT 5A WITH fADJ = 30.1k
C1, C3: TDK C3216X5R1E106MT C2: TAIYO YUDEN, JMK316BJ226ML C4: SANYO POSCAP, 6TPE330MIL
12V to 5V at 5A
VIN 7V TO 20V C3 10F 25V C1 10F 25V EXTVCC FCB LTM4602 RUN/SOFT-START RUN/SS COMP SGND SVIN PGOOD PGND
4602 F20b
R1 15k C5 100pF VOUT VOSET RSET 13.7k 1% OPEN DRAIN
VIN
fADJ
VOUT 5V AT 5A
EFFICIENCY = 92.5% AT 5A LOAD C2 22F
+
C4 330F 6.3V
7V TO 20V AT 5A WITH fADJ = 15k
C1, C3: TDK C3216X5R1E106MT C2: TAIYO YUDEN, JMK316BJ226ML C4: SANYO POSCAP, 6TPE330MIL
Figure 20. VIN to VOUT Step-Down Ratio for 12VIN to 5VOUT and 5VIN to 3.3VOUT
VIN 5V TO 20V GND
+
CIN 150F BULK
CIN 10F x2 CER EXTVCC
VIN (MULTIPLE PINS) VOUT (MULTIPLE PINS) VOUT 6A COUT1 REFER TO TABLE 2
C3 100pF VOUT RSET 66.5k REFER TO TABLE 1
SVIN fADJ VOSET COMP FCB C4 OPT PGOOD SGND
+
COUT2 REFER TO TABLE 2
LTM4602
RUN/SS PGND (MULTIPLE PINS)
0.6V TO 5V REFER TO STEP-DOWN RATIO GRAPH GND
4602 F21
Figure 21. Typical Application, 5V to 20V Input, 0.6V to 5V Output, 6A Max
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LTM4602 TYPICAL APPLICATION
Parallel Operation and Load Sharing
VIN 4.5V TO 20V C7 10F 25V EXTVCC FCB LTM4602 RUN COMP SGND RUN/SOFT-START SVIN PGOOD PGND VOUT 2.5V 12A C4 220pF VOUT VOSET LTM4602 RUN COMP SGND SVIN PGOOD PGND
4602 TA02
VOUT = 0.6V * ([100k/N] + RSET)/RSET WHERE N = 2 VIN fADJ VOUT VOSET RSET 15.8k 1% C9 22F
+
C10 330F 4V
C1 10F 25V EXTVCC FCB
VIN
fADJ
C2 22F R1 100k
+
C5 330F 4V
C1, C7: TDK C3216X5R1E106MT C2, C9: TAIYO YUDEN, JMK316BJ226ML-T501 C5, C10: SANYO POSCAP, 4TPE330MI
Current Sharing Between Two LTM4602 Modules
6 12VIN 2.5VOUT 12AMAX INDIVIDUAL SHARE 4 IOUT2 2
IOUT1
0 0 6 TOTAL LOAD 12
4602 TA03
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20
LGA Package 104-Lead (15mm x 15mm)
(Reference LTM DWG # 05-05-1800)
1.9042 0.0000 4.4442 6.9865
19 20 10 11 21 14 22 23 28 24 35 44 55 56 67 70 68 71 69 58 59 66 57 60 45 46 48 47 49 36 37 38 29 30 31 15
6.9421
5.7158
4.4458
3.1758
1.9058 0.6358
0.6342
3.1742
6.9888
6 16 7 17 18
2
3
4
5
6.5475
1
5.7650 2.72 - 2.92 aaa Z 15 BSC X Y
9
5.2775
8
4.4950
13
4.0075
12
2.7375 4 PAD 1 CORNER
25
2.3600
26
27
1.4675
32
1.0900
33
34
PACKAGE DESCRIPTION
0.0000
0.3175 0.3175
39
40
41
42
43
1.2700
50
51
52
53
54
5.7142
15 BSC
2.5400
61
62
63
64
65
4.4450
88 89 92 93 90 91
72 77 78 81 79 80 82
73
74
75
76
MOLD CAP SUBSTRATE
5.7150 0.27 - 0.37
99 104 100 101 102 103
83
84
85
86
87
6.9850 2.45 - 2.55 DETAIL B 0.3175 0.3175 1.2700 3.8100 6.3500 bbb Z Z
94
95
96
97
98
3.8100
6.3500
5.0800
2.5400
1.2700
2.5400
0.0000
5.0800
aaa Z
SUGGESTED SOLDER PAD LAYOUT TOP VIEW
12.70 BSC
99 104 93 82 88 92 81 77 78 79 80 89 90 91 100 101 102 103
TOP VIEW
DETAIL B
0.11 - 0.27
94
95
96
97
98
PADS SEE NOTES T 3 R P
NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS 3 4 LAND DESIGNATION PER JESD MO-222, SPP-010
83
84
85
86
87
72
73
74
75
76
61 55 59 48 49 56 57 58 60
62
63 71
64
65
66
67
68
69
70
N M L K H G F E
21
50 44 35 24 36 37 38 45 46 47
51
52
53
54
DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PAD #1 IDENTIFIER IS A MARKED FEATURE OR A NOTCHED BEVELED PAD 5. PRIMARY DATUM -Z- IS SEATING PLANE 6. THE TOTAL NUMBER OF PADS: 104
13.97 BSC
39
40
41
42
43
33
34
32 28 23 22 14 15 29 30 31
J
26
27
25
12
13
8 10 20 6 7 16 17 18 19 11
D C B A eee M X Y
SYMBOL TOLERANCE aaa 0.15 bbb 0.10 eee 0.15
9
1
2
3
4
5
C(0.30) PAD 1 13 12 13.93 BSC 14 16 18 20 15 17 19 21 22
1
3
5
7
9
11
23
LTM4602
21
2
4
6
8
10
LGA104 0206
4602fa
BOTTOM VIEW
LTM4602 PACKAGE DESCRIPTION
Pin Assignment Tables (Arranged by Pin Number)
PIN NAME A1 A2 A3 VIN A4 A5 VIN A6 A7 VIN A8 A9 VIN A10 A11 VIN A12 A13 VIN A14 A15 fADJ A16 A17 SVIN A18 A19 EXTVCC A20 A21 VOSET A22 A23 PIN NAME J1 PGND J2 J3 J4 J5 J6 J7 J8 J9 J10 J11 J12 J13 J14 J15 J16 J17 J18 J19 J20 J21 J22 J23 PGOOD PIN NAME B1 VIN B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 B13 B14 B15 B16 B17 B18 B19 B20 B21 B22 B23 COMP PIN NAME K1 K2 K3 K4 K5 K6 K7 PGND K8 K9 PGND K10 K11 PGND K12 K13 PGND K14 K15 PGND K16 K17 PGND K18 K19 K20 K21 K22 K23 PIN NAME C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 VIN C11 C12 VIN C13 C14 VIN C15 C16 C17 C18 C19 C20 C21 C22 C23 PIN NAME L1 L2 PGND L3 L4 PGND L5 L6 PGND L7 L8 PGND L9 L10 PGND L11 L12 PGND L13 L14 PGND L15 L16 PGND L17 L18 PGND L19 L20 PGND L21 L22 PGND L23 PIN NAME D1 VIN D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 D19 D20 D21 D22 D23 SGND PIN NAME M1 M2 PGND M3 M4 PGND M5 M6 PGND M7 M8 PGND M9 M10 PGND M11 M12 PGND M13 M14 PGND M15 M16 PGND M17 M18 PGND M19 M20 PGND M21 M22 PGND M23 PIN NAME E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 VIN E11 E12 VIN E13 E14 VIN E15 E16 E17 E18 E19 E20 E21 E22 E23 PIN NAME N1 N2 PGND N3 N4 PGND N5 N6 PGND N7 N8 PGND N9 N10 PGND N11 N12 PGND N13 N14 PGND N15 N16 PGND N17 N18 PGND N19 N20 PGND N21 N22 PGND N23 PIN NAME F1 VIN F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 RUN/SS PIN NAME P1 P2 VOUT P3 P4 VOUT P5 P6 VOUT P7 P8 VOUT P9 P10 VOUT P11 P12 VOUT P13 P14 VOUT P15 P16 VOUT P17 P18 VOUT P19 P20 VOUT P21 P22 VOUT P23 PIN NAME G1 PGND G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 G14 G15 G16 G17 G18 G19 G20 G21 G22 G23 FCB PIN NAME R1 R2 VOUT R3 R4 VOUT R5 R6 VOUT R7 R8 VOUT R9 R10 VOUT R11 R12 VOUT R13 R14 VOUT R15 R16 VOUT R17 R18 VOUT R19 R20 VOUT R21 R22 VOUT R23 PIN NAME H1 H2 H3 H4 H5 H6 H7 PGND H8 H9 PGND H10 H11 PGND H12 H13 PGND H14 H15 PGND H16 H17 PGND H18 H19 H20 H21 H22 H23 PIN NAME T1 T2 VOUT T3 T4 VOUT T5 T6 VOUT T7 T8 VOUT T9 T10 VOUT T11 T12 VOUT T13 T14 VOUT T15 T16 VOUT T17 T18 VOUT T19 T20 VOUT T21 T22 VOUT T23 4602fa
22
LTM4602 PACKAGE DESCRIPTION
Pin Assignment Tables (Arranged by Pin Number)
PIN NAME G1 H7 H9 H11 H13 H15 H17 J1 K7 K9 K11 K13 K15 K17 L2 L4 L6 L8 L10 L12 L14 L16 L18 L20 L22 M2 M4 M6 M8 M10 M12 M14 M16 M18 M20 M22 N2 N4 N6 N8 N10 N12 N14 N16 N18 N20 N22 PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND P2 P4 P6 P8 P10 P12 P14 P16 P18 P20 P22 R2 R4 R6 R8 R10 R12 R14 R16 R18 R20 R22 T2 T4 T6 T8 T10 T12 T14 T16 T18 T20 T22 PIN NAME VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT VOUT A3 A5 A7 A9 A11 A13 B1 C10 C12 C14 D1 E10 E12 E14 F1 PIN NAME VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN A15 A17 A19 A21 B23 D23 F23 G23 J23 PIN NAME fADJ SVIN EXTVCC VOSET COMP SGND RUN/SS FCB PGOOD
4602fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTM4602 TYPICAL APPLICATION
1.8V, 6A Regulator
VIN 4.5V TO 20V C2 10F 25V C1 10F 25V EXTVCC FCB LTM4602 RUN COMP SGND SVIN PGOOD PGND
4602 TA04
VIN
fADJ VOUT VOSET
C5 100pF
VOUT 1.8V AT 6A C3 22F
+
R1 100k
C4 330F 4V
PGOOD RSET 49.9k 1% C1, C2: TDK C3216X5R1E106MT C3: TAIYO YUDEN, JMK316BJ226ML-T501 C4: SANYO POSCAP, 4TPE330MI
RELATED PARTS
PART NUMBER LTC2900 LTC2923 LT3825/LT3837 LTM4600 LTM4601 LTM4603 DESCRIPTION Quad Supply Monitor with Adjustable Reset Timer Power Supply Tracking Controller Synchronous Isolated Flyback Controllers 10A DC/DC Module 12A DC/DC Module with PLL, Output Tracking/ Margining and Remote Sensing 6A DC/DC Module with PLL and Output Tracking/ Margining and Remote Sensing COMMENTS Monitors Four Supplies; Adjustable Reset Timer Tracks Both Up and Down; Power Supply Sequencing No Optocoupler Required; 3.3V, 12A Output; Simple Design 10A Basic DC/DC Module Synchronizable, PolyPhase(R) Operation, LTM4601-1 Version has no Remote Sensing, Fast Transient Response Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote Sensing, Fast Transient Response
PolyPhase is a registered trademark of Linear Technology Corporation.
This product contains technology licensed from Silicon Semiconductor Corporation.
(R)
4602fa
24 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0807 REV A * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007

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