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SP7663
Wide Input Voltage Range 6A, 600kHz, Buck Regulator
FEATURES
4.75V to 22V Input Voltage Range using Single Supply 3V to 22V Input Voltage Range using Dual Supply % 0.8V Reference 6A Output Capability Current Limiting using Inductor DCR Built in Low RDS(ON) Power Switches 600 kHz Fixed Frequency Operation Over Temperature Protection Short Circuit Protection with Auto-Restart Wide BW Amp Allows Type II or III Compensation Programmable Soft Start Fast Transient Response HighEfficiency:Greaterthan95% Possible Nonsynchronous Start-Up into a Pre-Charged Output AvailableinRoHSCompliant,LeadFreePackaging: Small 7mm x 4mm DFN U.S. Patent #6,922,04
LX LX LX LX
26
PowerBlox
SP7663
TM
DFN PACKAGE 7mm x 4mm (Option 2) 1 BOTTOM VIEW Heatsink Pad 1 Connect to Lx PGND
25 24
23
2 PGND 3 PGND 4 PGND
VCC 2 2 UVIN 21 GND 20 GND 19 VIN 18 BST 17 LX 16 LX 15 LX 14
Pin 27
5 GND 6 VFB
Heatsink Pad 2 Connect to GND Pin 28 Heatsink Pad 3 Connect to VINP Pin 29
7 COMP 8 SS
9 GND 10 ISN 11 ISP 12 SWN 13 VINP
DESCRIPTION
TheSP7663isasynchronousstep-downswitchingregulatoroptimizedforhighefficiency.Thepartisdesigned for use with a single 4.75V to 22V single supply or 3V to 22V input if an external Vcc is provided. The SP7663 providesafullyintegratedbuckregulatorsolutionusingafixed600kHzfrequency,PWMvoltagemodearchitecture. Protection features include UVLO, thermal shutdown, output current limit and short circuit protection. The SP7663 is available in the space saving DFN package.
TYPICAL APPLICATION CIRCUIT
VOUT
VIN
12V
C2 22uF
C1 22uF
LX
L1 1.5uH, 5.5 mOhm R3 4.99k C4 R4 4.99k 0.1uF
3.30V, 0-6A
28
SWN PAD
GND PAD
GND
1 2 PGND PGND PGND PGND GND VFB COMP SS GND ISN ISP SWN VIN
27
LX LX
26 25 24 23 22 21 20 19 18 17 16 15 14
RZ3 3.09k
C5 100uF
CZ2 270pF CP1
RZ2 75k,1% 10pF
3 4 5 6 7
U1 SP7663
ISP
ISN
LX LX VCC UVIN GND GND VIN BST LX LX LX
CZ3 180pF R1 68.1k,1% R2
CVCC 4.7uF
GND
NC
21.5k,1%
CF1 100pF
CSS
47nF
8 9 10 11
ISN
C9
6.8nF
12 13
VIN PAD
6.8nF CBST
SD101AWS DBST
ISP LX
R13 3.3 Rs1
29
LX
Cs1
Rs2
Cs2
1 Ohm
2.2nF
1 Ohm
2.2nF
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections ofthespecificationsbelowisnotimplied.Exposuretoabsolutemaximumratingconditionsforextendedperiodsoftimemayaffectreliability. VCC ...................................................................................................7V ViN .................................................................................................25V BST................................................................................................ 30V LX-BST ...............................................................................-0.3V to 7V LX ........................................................................................-V to 30V All other pins .......................................................... -0.3V to VCC + 0.3V Storage Temperature ................................................... -65C to 50C Power Dissipation ........................................Internally Limited via OTP Lead Temperature (Soldering, 0 sec) .......................................300C ESD Rating ........................................................................... 2kVHBM Thermal Resistance JC............................................................ 5C/W
SpecificationsareforTAMB = TJ = 25C, and those denoted by apply over the full operating range, -40C< Tj< 25C. Unless otherwisespecified:4.5VELECTRICAL SPECIFICATIONS
CONDITIONS
VfB= 0.9V
PARAMETER
QUIESCENT CURRENT ViN Supply Current (No switching) ViN Supply Current (switching) BST Supply Current (No switching) BST Supply Current (switching) PROTECTION: UVLO
MIN
TYP
.5 8 0.2 3
MAX UNITS
3.0 20 0.4 6 mA mA
mA mA
V mV V
VfB= 0.9V
Vcc UVLO Start Threshold 4.00 Vcc UVLO Hysteresis UVIN Start Threshold UVIN Hysteresis UVIN Input Current 00 2.30 200
4.25 200 2.50 300
4.50 300 2.65 400 .0

mV A
UVIN=3.0V
ERROR AMPLIFIER REFERENCE ErrorAmplifierReference 0.792 0.800 0.808 0.784 0.800 0.86 70 -230 3.2 50 -50 50 3.5 -2.0 230 -70 200 3.8 V V
2XGainConfig.,Measure VfB; Vcc=5V
ErrorAmplifier Reference Over Line COMPSinkCurrent COMPSourceCurrent VfB Input Bias Current COMPClamp COMPClampTemp. Coefficient
VCC LINEAR REGULATOR

VfB=0.9V,COMP=0.9V VfB=0.9V,COMP=0.9V VfB=0.8V VfB=0.7V, TA=25C
A A
nA V mV/C
VCC Output Voltage
4.7 4.5 250
5.0 4.73 500
5.3
V

Dropout Voltage
750
mV
ViN = 6 to 23V, ILOAD = 0mA to 30mA ViN = 5V, 20mA Vin-Vout = Dropout voltage when Vcc regulated drops by 2%. IVCC = 30mA.
(c) 2007 Sipex Corporation
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
2
SpecificationsareforTAMB = TJ = 25C, and those denoted by apply over the full operating range, -40C< Tj< 25C. Unless otherwisespecified:4.5VELECTRICAL SPECIFICATIONS
PARAMETER
Ramp Amplitude RAMPOffset Ramp offset Temperature Coefficient GHMinimumPulseWidth MaximumControllable Duty Ratio MaximumDutyRatio Internal Oscillator Ratio TIMERS: SOFTSTART SSChargeCurrent: SSDischargeCurrent: Short Circuit Threshold Voltage
MIN TYP MAX UNITS
0.80 .7 .00 2.0 -2 50 92 00 50 -6 .0 600 -0 2.0 690 -4.0 3.0 97 80 .20 2.3 V V mV/C ns % % kHZ
CONDITIONS
CONTROL LOOP: PWM COMPARATOR, RAMP & LOOP DELAY PATH

Fault Present, SS=0.2V Valid for 20 cycles
A
mA
PROTECTION: SHORT CIRCUIT, OVERCURRENT & THERMAL 0.2 0.25 220 60 0.3 V ms

VfB=0.5V MeasuredISP-ISN
Hiccup Timeout Overcurrent Threshold 54 Voltage ISP,ISNCommonMode 0 Range Thermal Shutdown 35 Temperature Thermal Recovery Temperature Thermal Hysteresis
OUTPUT: POWER STAGE
66
3.6
mV
V C C C
Guaranteedbydesign
45 35 0
55
High Side Switch RDSON Synchronous Low Side Switch RDSON MaximumOutput Current
6
6.8 6.8
20.5 20.5
m m A
VGS=4.5V; IDrAiN=5A; TAMB=25C VGS=4.5V; IDrAiN=5A; TAMB=25C
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
3
CONTROLLER BLOCK DIAGRAM
VC C
C OMP SS V FB INT 1.6 V
A S Y NC . S TAR TUP C OMP A R A TOR GL HOLD OFF BS T
V FB VCC 10 uA S OFTS TA R T INP UT SS 0.1V
P W M LO O P
VC C Gm ER R OR A MP LIFIE R FA ULT RE S E T DOMINA NT R Q P OS R E F FAULT S QP W M
GH
VPOS
Gm
S Y NC HR O NO US DR I V E R
S WN GL
FA ULT
600 kHZ P GN D C LK C LOC K P ULS E GEN E R A TOR 2.8 V 1.3 V FAULT
R AMP =1V
V CC
R E FE R E NC E C OR E
0.8V R E F OK
PO W E R FA ULT 4.25 V ON 4.05 V OFF 145C O N 135C O FF VC C UV LO
THE R MA L S HUTDOW N
SET DOMINA NT S Q HIC C UP FAULT
0.25V VP OS 5V LINE A R R E GULA TOR V FB INT
S HOR TC IR C UIT DE TE C TION
R
GND 200ms D elay OV E R C UR R E NT DE TE C TION C OU NTE R C LK
V IN 60 mV R E F OK
C LR
140K UV IN 2.50 V ON 2.20 V O FF 50K VIN UV LO
IS P
IS N
T HE R MA L A ND O V E R C UR R E NT P R O T E C T IO N
UV LO C O MP A R AT O R S
Note: The SP7663 uses the Sipex PWM controller SP6136.
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SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
4
PIN DESCRIPTION
SP7663
DFN PACKAGE 7mm x 4mm (Option 2) LX 26 LX 25 LX 24 LX 23 VCC 22 UVIN 21 GND 20 GND 19 VIN 18 BST 17 LX 16 LX 15 LX 14 Heatsink Pad 3 Connect to VINP Pin 29 Heatsink Pad 2 Connect to GND Pin 28 Pin 27 1 PGND 2 PGND 3 PGND 4 PGND 5 GND 6 VFB 7 COMP 8 SS 9 GND 10 ISN 11 ISP 12 SWN 13 VINP
BOTTOM VIEW Heatsink Pad 1 Connect to Lx
Pin Pin # Name Description -4 PGND Groundconnectionforthesynchronousrectifier. GroundPin.ThecontrolcircuitryoftheICandlowerpowerdriverarereferencedtothis 5, 9, GND 9, 20 pin. Return separately from other ground traces to the (-) terminal of COut. Feedback Voltage and Short Circuit Detection pin. It is the inverting input of the Error Amplifier and serves as the output voltage feedback point for the Buck Converter. The output voltage is sensed and can be adjusted through an external resistor divider. Whenever VFB drops 0.25V below the positive reference, a short circuit fault is detected and the IC enters hiccup mode.
6
VFB
7
8 0 2 3
4-6, 23-26
OutputoftheErrorAmplifier.Itisinternallyconnectedtotheinvertinginputofthe COMP PWMcomparator.Anoptimalfiltercombinationischosenandconnectedtothis pin and either ground or VFB to stabilize the voltage mode loop. SoftStart.ConnectanexternalcapacitorbetweenSSandGNDtosetthesoftstart SS rate based on the 0A source current. The SS pin is held low via a mA (min) current during all fault conditions. ISN Current sense negative input. Rail-to-rail input for overcurrent detection. ISP SWN VINP LX BST VIN UVIN VCC Current sense positive input. Rail-to-rail input for overcurrent detection. LowersupplyrailfortheGHhigh-sidegatedriver.Connectthispintotheswitching node as close as possible to pins 23- 27. Do not connect this pin to pins 4 - 6. InputconnectiontothehighsideN-channelMOSFET. Connect an inductor between this pin and VOut. High side driver supply pin. Connect BST to the external boost diode and capacitor as shown in the Typical Application Circuit on page . The high side driver is connected between BST pin and SWN pin. ViNconnectionforinternalLDOandPWMController. UVLO input for ViN voltage. Connect a resistor divider between ViN and UVIN tosetminimumoperatingvoltage.Useresistorvaluesbelow20ktooverride internal resistor divider. Outputofinternalregulator.MaybeexterinallybiasedifVin<5V.
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator (c) 2007 Sipex Corporation
7 8 2 22
Feb2-07 Rev O
5
THEORY OF OPERATION General Overview The SP7663 is a fixed frequency, voltage mode, synchronous PWM regulator optimizedforhighefficiency.Theparthas beenspecificallydesignedforsinglesupply operation from a 5V to 22V input. The heart of the SP7663 is a wide bandwidth transconductanceamplifierdesignedtoaccommodate Type II and Type III compensation schemes. A precision 0.8V reference, present on the positive terminal of the error amplifier, permits the programming of the output voltage down to 0.8V via the VFB pin.Theoutputoftheerroramplifier,COMP, is compared to a .0V peak-to-peak ramp, whichisresponsiblefortrailingedgePWM control.ThisvoltagerampandPWMcontrol logic are governed by the internal oscillator thataccuratelysetsthePWMfrequencyto 600kHz. The SP7663 contains two unique control features that are very powerful in distributed applications. First, nonsynchronous driver control is enabled during startup, to prohibit the low side switch from pulling down the output until the high side switch has attempted to turn on. Second, a 00% duty cycle timeout ensures that the low side switch is periodically enhanced during extended periods at 00% duty cycle. This guarantees the synchronized refreshing of the BST capacitor during very large duty ratios. The SP7663 also contains a number of valuable protection features. Programmable VIN UVLO allows the user to set the exact value at which the conversion voltage can safely begin down-conversion, and an internal VCC UVLO which ensures that the controller itself has enough voltage to properly operate. Other protection features include thermal shutdown and short-circuit detection. In the event that either a thermal, short-circuit, or UVLO fault is detected, the SP7663 is forced into an idle state where the output drivers areheldoffforafiniteperiodbeforearestart is attempted.
Feb2-07 Rev O
Soft Start "Soft Start" is achieved when a power converter ramps up the output voltage while controlling the magnitude of the input supply source current. In a modern step down converter, ramping up the positive terminal oftheerroramplifiercontrolssoftstart.Asa result,excesssourcecurrentcanbedefined as the current required to charge the output capacitor. IViN = COut * (VOut / TSOft-StArt) The SP7663 provides the user with the option to program the soft start rate by tying a capacitor from the SS pin to GND.The selection of this capacitor is based on the 0A pull up current present at the SS pin and the 0.8V reference voltage. Therefore, theexcesssourcecanberedefinedas: IViN = COut * [VOut *0A / (CSS * 0.8V)]
Under Voltage Lock Out (UVLO) The SP7663 has two separate UVLO comparators to monitor the bias (Vcc) and Input (ViN) voltages independently. The Vcc UVLO is internally set to 4.25V. The ViN UVLO is programmable through UViN pin. When UVIN pin is greater than 2.5V the SP7663 is permitted to start up pending the removal of all other faults. A pair of internal resistors isconnectedtoUVINasshowninthefigure below. SP7663
VIN
R6 UVIN
140K
R7 GND
2.5V ON 2.2V OFF 50K
+
Internal and external bias of UVIN
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
6
THEORY OF OPERATION Therefore without external biasing the ViN start threshold is 9.5V. A small capacitor mayberequiredbetweenUVINandGNDto filteroutnoise.ForapplicationswithViN of 5V or 3.3V, connect UVIN directly to ViN. To program the ViN start threshold, use a pair of external resistors as shown. If external resistors are an order of magnitude smaller than internal resistors, then the ViN start thresholdisgivenby: ViN(start) = 2.5 V* (R6+R7)/R7 For example, if it is required to have a ViN startthresholdof7V,thenletR7=5Kand using the ViN start threshold equation we get R5=9.09K. Thermal and Short-Circuit Protection Because the SP7663 is designed to drive large output current, there is a chance that the power converter will become too hot. Therefore, an internal thermal shutdown (45C) has been included to prevent the IC from malfunctioning at extreme temperatures. A short-circuit detection comparator has also been included in the SP7663 to protect against an accidental short at the output of the power converter. This comparator constantly monitors the positive and negative terminals of the error amplifier, and if the VfB pin falls more than 250mV (typical) below the positive reference, a short-circuit fault is set. Because the SS pin overrides the internal 0.8V reference during soft start, the SP7663 is capable of detecting short-circuit faults throughout the duration of soft start as well as in regular operation. Over-Current Protection The Over-current protection feature can onlybeusedonoutputvoltages3.3volts. It is limited by the common mode rating of theoperationalamplifierusedtosensethe voltage across the inductor. Over-current is detected by monitoring a differential voltage
Feb2-07 Rev O
across the output inductor as shown in the nextfigure.
SP7663
SWN
L = 1.5uH, DCR = 9.2m
VOUT
R3 5.11K
R4 5.11K
ISP ISN CSP 6.8nF CS 0.1uF
Over-current detection circuit Inputs to an over-current detection comparator, set to trigger at 60 mV nominal, are connected to the inductor as shown. Since the average voltage sensed by the comparator is equal to the product of inductor current and inductor DC resistance (DCR), then IMAx = 60mV / DCR. Solving thisequationforthespecificinductorincircuit , IMAx = 9.2A. When IMAx is reached, a 20 ms time-out is initiated, during which top and bottom drivers are turned off. Following the time-out, a restart is attempted. If the fault condition persists, then the timeout is repeated (referred to as hiccup). Increasing the Current Limit If it is desired to set IMAx > {60mV / DCR} (in this case larger than 9.6A), then a resistor R9 shouldbeaddedasshowninthenextfigure. R9 forms a resistor divider and reduces the voltage seen by the comparator. (IMAx * DCR) Since:60mV = R9 {R3 + R4 + R9} SolvingforR9weget: R9 = [60mV * (R3 + R4)] [(IMAx * DCR) - 60mV]
(c) 2007 Sipex Corporation
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
7
THEORY OF OPERATION Asanexample:ifdesiredIMAx is 9A, then R9 = 26.4k. Asanexample:forIMAx of 5A and VOut of 3.3V, calculatedR8is1.1M.
SP7663
SWN L = 1.5uH, DCR = 9.2m
VOUT
SP7663
SWN L = 1.5uH, DCR = 9.2m
VOUT
R3 5.11K R9 26.4K CSP 6.8nF CS 0.1uF
R4 5.11K
R3 5.11K
R4 5.11K
ISP ISN
ISP ISN CSP 6.8nF CS 0.1uF R8 1.1M
Over-current detection circuit for Imax > 60mV / DCR Decreasing the Current Limit If it is required to set IMAx < {60mV / DCR, a resistor is added as shown in the following figure.R8increasesthenetvoltagedetected by the current-sense comparator. Voltage at the positive and negative terminal of comparatorisgivenby: VSP = VOut + (IMAx * DCR) VSN = VOut * {R8 / (R4 +R8)} Sincethecomparatoristriggeredat60mV: VSP-VSN = 60 mV Combining the above equations and solvingforR8: R8 = R4 * [VOut - 60mV + (IMAX* DCR)] 60mV - (IMAX * DCR)
Over-current detection circuit for Imax < {60mV / DCR} Handling of Faults Upon the detection of power (UVLO), thermal, or short-circuit faults, the SP7663 is forced into an idle state where the SS and COMPpinsarepulledlowandbothswitches are held off. In the event of UVLO fault, the SP7663 remains in this idle state until the UVLO fault is removed. Upon the detection of a thermal or short-circuit fault, an internal 20ms timer is activated. In the event of a short-circuit fault, a restart is attempted immediately after the 20ms timeout expires. Whereas, when a thermal fault is detected the 20ms delay continuously recycles and a restart cannot be attempted until the thermal fault is removed and the timer expires.
Error Amplifier and Voltage Loop The heart of the SP7663 voltage error loop is a high performance, wide bandwidth transconductance amplifier. Because of
(c) 2007 Sipex Corporation
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
8
APPLICATIONS INFORMATION theamplifier'scurrentlimited(+/-150A) transconductance, there are many ways to compensate the voltage loop or to control the COMPpinexternally.Ifasimple,single-pole, single-zero response is desired, then compensation can be as simple as an RC circuit toGround.Ifamorecomplexcompensation isrequired,thentheamplifierhasenough bandwidth(45at4MHz),andenoughgain (60dB) to run Type III compensation schemes with adequate gain and phase margins at crossover frequencies greater than 50kHz. The common mode output of the error amplifieris0.9Vto2.2V.Therefore,thePWM voltage ramp has been set between .V and 2.2V to ensure proper 0% to 00% duty cycle capability. The voltage loop also includes two other very important features. One is a nonsynchronous startup mode. Basically, the synchronousrectifiercannotturnonunless the high side switch has attempted to turn on or the SS pin has exceeded .7V. This feature prevents the controller from "dragging down" the output voltage during startup or in fault modes.
VBST GH Voltage VSWN V(VCC) GL Voltage 0V V(VIN) SWN Voltage -0V -V(Diode) V V(VIN)+V(VCC) BST Voltage V(VCC) TIME
ratios. In the event that the high side NFET is on for 20 continuous clock cycles, a reset isgiventothePWMflipflophalfwaythrough the 2stcycle.ThisforcesGLtoriseforthe cycle, in turn refreshing the BST capacitor. The boost capacitor is used to generate a high voltage drive supply for the high side switch, which is Vcc above ViN. Power MOSFETs The SP7663 contains a pair of integrated low resistance N-channel switches designed to drive up to 6A of output current. Care should be taken to de-rate the output current based on the thermal conditions in the system such as ambient temperature, airflow and heat sinking.Maximumoutputcurrentcouldbe limited by thermal limitations of a particular application by taking advantage of the integrated-over-temperature protective scheme employed in the SP7663. The SP7663 incorporates a built-in overtemperature protection to prevent internal overheating. Setting Output Voltages The SP7663 can be set to different output voltages. The relationship in the following formula is based on a voltage divider from the output to the feedback pin VfB, which is set to an internal reference voltage of 0.80V. Standard1%metalfilmresistorsofsurface mount size 0603 are recommended. VOut = 0.80V [R / R2 + ] =>
R2 = R / [ ( VOut / 0.80V ) - ]
The second feature is a 00% duty cycle timeout that ensures synchronized refreshing of the BST capacitor at very high duty
Feb2-07 Rev O
Where R1=10Kand forVOut = 0.80V setting, simply remove R2 from the board. Furthermore, one could select the value of the R and R2 combination to meet the exact output voltage setting by restricting the R resistance range such that 10K < R1 < 100Kforoverallsystemloopstability.
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
9
APPLICATIONS INFORMATION Inductor Selection There are many factors to consider in selecting the inductor including core material, inductance vs. frequency, current handling capability,efficiency,sizeandEMI.Inatypical SP7663 circuit, the inductor is chosen primarily for value, saturation current and DC resistance. Increasing the inductor value will decrease output voltage ripple, but degrade transient response. Low inductor values provide the smallest size, but cause large ripple currents,poorefficiencyandrequiremore output capacitance to smooth out the larger ripple current. The inductor must be able to handle the peak current at the switching frequency without saturating, and the copper resistance in the winding should be kept as low as possible to minimize resistive power loss. A good compromise between size, loss and cost is to set the inductor ripple current to be within 20% to 40% of the maximum output current. The switching frequency and the inductor operating point determine the inductor value asfollows: L =
.
and provide low core loss at the high switching frequency. Low cost powderediron cores have a gradual saturation characteristic but can introduce considerable AC core loss, especially when the inductor value is relatively low and the ripple current is high. Ferrite materials, although more expensive, have an abrupt saturation characteristic with the inductance dropping sharply when the peak design current is exceeded. Nevertheless, they are preferred at high switching frequencies because they present very low core loss while the designer is only required to prevent saturation. In general, ferrite or molypermalloy materials are a better choice for all but the most cost sensitive applications. Optimizing Efficiency The power dissipated in the inductor is equal to the sum of the core and copper losses. To minimize copper losses, the winding resistance needs to be minimized, but this usually comes at the expense of a larger inductor.Corelosseshaveamoresignificant contribution at low output current where the copper losses are at a minimum, and can typically be neglected at higher output currents where the copper losses dominate. Core loss information is usually available from the magnetics vendor. Proper inductor selection can affect the resulting power supplyefficiencybymorethan15%! The copper loss in the inductor can be calculatedusingthefollowingequation: PL(Cu) = I L(rMS) * rwiNDiNg where IL(rMS)istheRMSinductorcurrent thatcanbecalculatedasfollows: IL(rMS) = IOut(MAx) *
2
ViN(MAx) * s * Kr * IOut(MAx)
VOut * (ViN(MAx) - VOut)
where:
s = switching frequency
Kr = ratio of the AC inductor ripple current to the maximum output current Thepeak-to-peakinductorripplecurrentis: IPP =
.V
Out
ViN(MAx) * s *L
* (ViN(MAx) - VOut)
Once the required inductor value is selected, the proper selection of core material is based onpeakinductorcurrentandefficiencyrequirements. The core must be large enough not to saturate at the peak inductor current IPP IPeAk = IOut(MAx) + 2
( )
+ 3
.
IPP IOut(MAx)
2
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SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
0
APPLICATIONS INFORMATION Output Capacitor Selection The required ESR (Equivalent Series Resistance) and capacitance drive the selection of the type and quantity of the output capacitors. The ESR must be small enough that both the resistive voltage deviation due to a step change in the load current and the output ripple voltage do not exceed the tolerance limits expected on the output voltage. During an output load transient, the output capacitor must supply all the additional current demanded by the load until the SP7663 adjusts the inductor current to the new value. In order to maintain VOut,the capacitance must be large enough so that the output voltage is held up while the inductor current ramps to the value corresponding to the new load current. Additionally, the ESR in the output capacitor causes a step in the output voltage equal to the current. Because of the fast transient response and inherent 00% to 0% duty cycle capability provided by the SP7663 when exposed to output load transients, the output capacitor is typically chosen for ESR, not for capacitance value. The ESR of the output capacitor, combined with the inductor ripple current, is typically the main contributor to output voltage ripple. The maximum allowable ESR required to maintain a specifiedoutputvoltageripplecan be calculated by: ReSr VOut IPk-Pk VOut =
s = Switching Frequency
D = Duty Cycle COut = Output Capacitance Value
Input Capacitor Selection
(
IPP * ( - D)
s * COut
)
2
+ (IPP *ReSr)
2
The input capacitor should be selected for ripple current rating, capacitance and voltage rating. The input capacitor must meet the ripple current requirement imposed by the switching current. In continuous conduction mode, the source current of thehigh-sideMOSFETisapproximatelya square wave of duty cycle VOut/ViN.More accurately, the current wave form is trapezoidal,givenafiniteturn-onandturn-off, switchtransitionslope.Mostofthiscurrent is supplied by the input bypass capacitors.TheRMScurrenthandlingcapability of the input capacitors is determined at maximum output current and under the assumption that the peak-to-peak inductor ripplecurrentislow,itisgivenby:
ICiN(rMS) = IOut(MAx) * D(1 - D)
The worst case occurs when the duty cycle Dis50%andgivesanRMScurrentvalue equal to IOUT/2. Select input capacitors with adequate ripple current rating to ensure reliable operation. The power dissipated in the input capacitoris: PCiN = I CiN(rMS) * reSr(CiN) Thiscanbecomeasignificantpartofpower losses in a converter and hurt the overall energy transfer efficiency. The input voltage ripple primarily depends on the input
2
where:
VOut = Peak-to-Peak Output Voltage Ripple IPk-Pk = Peak-to-Peak Inductor Ripple Current The total output ripple is a combination of the ESR and the output capacitance value andcanbecalculatedasfollows:
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
APPLICATIONS INFORMATION capacitor ESR and capacitance. Ignoring the inductor ripple current, the input voltage ripplecanbedeterminedby: ViN = Loop Compensation Design The open loop gain of the whole system can be divided into the gain of the error amplifier,PWMmodulator,buckconverteroutput stage, and feedback resistor divider. In order to cross over at the desired frequency cut-off (FCO),thegainoftheerroramplifiermust compensate for the attenuation caused by the rest of the loop at this frequency. The goal of loop compensation is to manipulate loop frequency response such that its crossover gain at 0db, results in a slope of -20db/decade. The first step of compensation design is to pick the loop crossover frequency. High crossover frequency is desirable for fast transient response, but often jeopardizes the power supply stability. Crossover frequency should be higher than the ESR zero but less than /5 of the switching frequency or
IOut(MAx)*reSr(CiN) + IOut(MAx)*VOut*(ViN - VOut) V2iN * s * CiN
The capacitor type suitable for the output capacitors can also be used for the input capacitors. However, exercise extra caution when tantalum capacitors are used. Tantalum capacitors are known for catastrophic failure when exposed to surge current, and input capacitors are prone to such surge current when power supplies are connected "live" to low impedance power sources. Although tantalum capacitors have been successfully employed at the input, it is generally not recommended.
Type III Voltage Loop Compensation GAMP (s) Gain Block VREF (Volts) (SRz2Cz2+1)(SR1Cz3+1) SR1Cz2(SRz3Cz3+1)(SRz2Cp1+1) Notes: RESR = Output Capacitor Equivalent Series Resistance. RDC = Output Inductor DC Resistance. VRAMP_PP = SP7662 Internal Ramp Amplitude Peak-to-Peak Voltage. Condition: Cz2 >> Cp1 & R1 >> Rz3 Output Load Resistance >> RESR & RDC
PWM Stage GPWM Gain Block VIN VRAMP_PP
Output Stage GOUT (s) Gain Block (SRESRCOUT+ 1) [S^2LCOUT+S(RESR+RDC) COUT+1]
VOUT (Volts)
Voltage Feedback GFBK Gain Block R2 VFBK (Volts) (R1 + R2) or VREF VOUT
SP7663 Voltage Mode Control Loop with Loop Dynamic
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
2
APPLICATIONS INFORMATION 60kHz. The ESR zero is contributed by the ESR associated with the output capacitors andcanbedeterminedby:
P(LC) =
.
2* L * COut
Z(ESR) =
2* COut * ReSr
The next step is to calculate the complex conjugate poles contributed by the LC outputfilter,
Gain (dB)
When the output capacitors are of a Ceramic Type, the SP7663 Evaluation Board requires a Type III compensation circuit to give a phase boost of 80 in order to counteract the effects of an underdamped resonance of the output filteratthedoublepolefrequency.
Condition: C22 >> CP1, R1 >> RZ3
Error Amplifier Gain Bandwidth Product
20 Log (RZ2/R1)
1/6.28 (RZ2) (CP1)
1/6.28 (RZ3) (CZ3)
1/6.28 (R1) (CZ3)
1/6.28(R22) (CZ2)
1/6.28 (R1) (CZ2)
Frequency (Hz)
Bode Plot of Type III Error Amplifier Compensation.
CP1
RZ3
CZ3
CZ2 VFB RSET
RZ2
VOUT
R1 68.1k, 1%
+ + - 0.8V
COMP CF1
RSET =
54.48 (k) (VOUT -0.8)
Type III Error Amplifier Compensation Circuit
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
3
VIN
12V
VOUT
C2 22uF
LX
C1 22uF
L1 1.5uH, 5.5 m R3 4.99k C4 R4 4.99k .1uF
3.30V, 0-6A
28
SWN PAD
GND PAD
GND
1 PGND PGND PGND PGND GND VFB COMP SS GND ISN 11 ISP 12 13 SWN VIN LX 25 24 23 22 VCC UVIN GND GND VIN BST LX LX
VIN PAD
27
LX
26
RZ3
C5
2
3.09k
ISP ISN
100uF
CZ2
LX LX
RZ2 75k,1%
5 4
3
U1 SP7663
CZ3 CVCC 4.7uF
21 20 19 18 17 16 15
180pF
270pF CP1
6 7
R1 68.1k,1%
NC
CF1 100pF
8 9 10
CSS
47nF
ISN
C9
6.8nF
LX
14
6.8nF CBST R13 3.3
29
SD101AWS DBST
ISP
LX LX
Rs1 1 Ohm
Cs1 2.2nF
Rs2
Cs2
1 Ohm
2.2nF
Feb2-07 Rev O
Evaluation Board Schematic. Parts shown for 10 to 14Vin, 6Aout, Type III Compensation.
4
10pF
R2
GND
21.5k,1%
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs. Load at 16VIN
95 90
Efficiency (%)
85 80 75 70 65 60 0 2 3 Output Current (A) 4 5 6
Vout 3.3V Vout 2.5V Vout .8V
Efficiency vs. Load at 12VIN
95 90
Efficiency (%)
85 80 75 70 65 60 0 2 3 Output Current (A) 4 5 6
Vout 3.3V Vout 2.5V Vout .8V Vout .5V
Efficiency vs. Load at 5VIN
00 95
Efficiency (%)
90 85 80 75 70 65 60 0 2 3 Output Current (A) 4 5 6
Vo ut 3.3V Vo ut 2.5V Vo ut 1 .8V Vo ut 1 .5V Vo ut 1 .2V Vo ut .8V
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
5
TYPICAL PERFORMANCE CHARACTERISTICS
Vout Ripple
Vout Ripple
Output Ripple, No Load
Output Ripple, Iout=6A
Vout Vout Soft start Soft start
Vin
Iout 5A/div
Vin Iout 5A/div Start up response, Iout=6A
Start up Response, No Load
Vout Transient
Iout 2A/div
Load Step Response, Iout=3A -6A
Feb2-07 Rev O
Load Step Response, Iout=0A -6A
(c) 2007 Sipex Corporation
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
6
TYPICAL PERFORMANCE CHARACTERISTICS
Vout
Vout
Vin
Soft start
Iout 5A/div
Iout 5A/div
Output Current Limit Response
OCP Hiccup Response time Dead Short
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
7
PAckAgE: 26 Pin dfn
Feb2-07 Rev O
SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator
(c) 2007 Sipex Corporation
8
ORDERING INFORMATION
Part Number
Junction Temperature
Package
SP7663ER/TR..................................-40C to +25C............ ..............................26 Pin 7 X 4 DFN (Option 2) SP7663ER-L/TR...............................-40C to +25C.......................(Lead Free) 26 Pin 7 X 4 DFN (Option 2)
/TR = Tape and Reel Pack quantity is 3,000 26 pin DFN.
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas,CA95035 TEL:(408)934-7500 FAX:(408)935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. Feb2-07 Rev O SP7663 Wide Input Voltage Range 6A, 600kHz Buck Regulator (c) 2007 Sipex Corporation
9

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