General Description
The MAXM17515 is a fixed-frequency, step-down power
module in a thermally-efficient system-in-package (SiP)
package that operates from a 2.4V to 5.5V input
supply voltage and supports output currents up to 5A.
The device includes switch-mode power-supply controller,
dual n-channel MOSFET power switches, a fully shielded
inductor, as well as compensation components. The
device supports 0.75V to 3.6V programmable output
voltage. The high level of integration significantly reduces
design complexity, manufacturing risks, and offers a true
plug-and-play power-supply solution, reducing the time
to market.
The MAXM17515 is available in a thermally enhanced,
compact 28-pin, 10mm x 6.5mm x 2.8mm SiP
package and can operate over the -40°C to +125°C
industrial temperature range.
Applications
● FPGAandDSPPoint-of-LoadRegulator
● BaseStationPoint-of-LoadRegulator
● IndustrialControlEquipment
● Servers
● ATEEquipment
● MedicalEquipment
Benets and Features
● ReducesDesignComplexity,ManufacturingRisks,
and Time-to-Market
• CompleteIntegratedStep-DownPowerSupplyina
Single Package
• PassesEN55022(CISPR22)Class-BRadiated
andConductedEMIStandard
●SavesBoardSpaceinSpace-ConstrainedApplications
• Small Form Factor 6.5mm x 10mm x 2.8mm SiP
Package
• SimpliedPCBDesignwithasFewasFour
External Components
● OffersFlexibilityforPower-DesignOptimization
• 2.4Vto5.5VInputVoltageRange
• 0.75V to 3.6V Programmable Output Voltage
• 5A Output Current
• Fixed1MHzSwitchingFrequency
• EnableInput
• Power-GoodOutput
● ReducesPowerDissipation
• Upto94%Efciency
• Autoswitch,Light-Load,Pulse-SkippingMode
• HighImpedanceShutdown
• <1μAShutdownCurrent
● OperatesReliablyandReducesSystemDowntime
• Voltage-ControlledInternalSoft-Start
• Fault Protection
• Output Undervoltage/Overvoltage Protection
• Thermal-Fault Protection
• PeakCurrentLimit
• -40°C to +125°C Operation
Ordering Information appears at end of data sheet.
IN
IN
IN
IN
VCC
EN
GND GND GND
POK
FB
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
PGND
MAXM17515
VIN
5V
VOUT
1.1V, 5A
VCC 22µF
(OPTIONAL )
22µF
22.1kΩ
PGND
PGND
PGND
PGND
PGND
PGND
47.5kΩ
220µF
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efficiency Power Module
19-7429; Rev 1; 4/15
Typical Application Circuit
EVALUATION KIT AVAILABLE
INtoPGND .............................................................-0.3V to +6V
VCCtoGND ............................................................-0.3V to +6V
VCCtoIN ................................................................. -0.3V to +6V
ENtoGND ..............................................................-0.3V to +6V
FB,POKtoGND ...................................... -0.3V to (VCC + 0.3V)
OUT,EP3toGND ......................................-0.6V to (VIN + 0.3V)
PGNDtoGND ......................................................-0.3V to +0.3V
EP1toGND..........................................................-0.3V to +0.3V
EP2toPGND ......................................... -0.3V to + (VIN + 0.3V)
EP2toGND............................................ -0.6V to + (VIN + 0.3V)
ContinuousPowerDissipation(TA = +70°C)
28-PinSIP(derate37mW/°Cabove+70°C) ............2000mW
OperatingTemperatureRange ......................... -40°C to +125°C
Junction Temperature ...................................................... +125°C
StorageTemperatureRange ............................ -55°C to +150°C
LeadTemperature(soldering,10s) .................................+245°C
SiP
Junction-to-AmbientThermalResistance(qJA)...........25°C/W
Junction-to-CaseThermalResistance(qJC) .................6°C/W
(Note 1)
(VIN = VCC = VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.
See Typical Application Circuit.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INPUT SUPPLY (VIN)
INInputVoltageRange VIN
2.4 5.5 V
VIN = VCC 4.5 5.5
INUndervoltageThreshold Risingedge(100mVhysteresis) 2.05 2.19 2.4 V
INStandbySupplyCurrent IQVIN = VCC = 4.5V, no load 1 5.5 μA
VCC SUPPLY
VCCInputVoltageRange VCC 4.5 5.5 V
VCC Undervoltage Threshold Risingedge(160mVhysteresis) 3.9 4.2 4.5 V
VCC Shutdown Supply Current IVCC_SHD EN=GND,POKunconnected,measured
at VCC, TA = +25°C 0.1 1.0 μA
VCC Supply Current IVCC Regulatorenabled,noload,noswitching
(VFB = 1V) 62 135 μA
OUTPUT
Output Voltage Programmable
Range VOUT VIN = VCC = 5.2V, ILOAD = 2A
(see derating curve for VOUT > 2.5V) 0.754 3.6 V
UnityGainOutput-Voltage
Tolerance/FBaccuracy FB=OUT,noload 0.757 0.770 0.783 V
FBLoadRegulationAccuracy
(RDROOP) 2A<IOUT<5A,FB=OUT -7.5 -4.4 -1 mV/A
FBLineRegulationAccuracy FB=OUT,noload,2.4V<VIN < 5.5V 1.253 4.5 mV/V
FBInputBiasCurrent TA = -40°C to +125°C (Note 3) -0.1 -0.015 +0.1 μA
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
2
Note 1: PackagethermalresistanceswereobtainedusingthemethoddescribedinJEDECspecificationJESD51-7,usingafour-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Absolute Maximum Ratings
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.
Package Thermal Characteristics
Electrical Characteristics
(VIN = VCC = VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.
See Typical Application Circuit.) (Note 2)
Note 2: Limitsare100%testedatTA =+25°C.Maximumandminimumlimitsareguaranteedbydesignandcharacterizationover
temperature.
Note 3: DesignguaranteedbyATEcharacterization.Limitsarenotproductiontested.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
AverageOutputCurrentLimit VIN = 5V 5 8 A
EFFICIENCY
Efciency VIN = 5V, VOUT=1.1V,IOUT = 2A 86 %
VIN = 5V, VOUT=1.1V,IOUT = 5A 78
SWITCHING FREQUENCY
Switching Frequency fSW 0.9 11.1 MHz
SOFT-START
Soft-StartRampTime tSS 1.79 ms
Soft-StartFaultBlankingTime tSSLT 3 ms
POWER-GOOD OUTPUT (POK)
POKUpperTripThresholdand
Overvoltage-Fault Threshold Risingedge,50mVhysteresis 830 850 870 mV
POKLowerTripThreshold Falling edge, 50mV hysteresis 658 690 725 mV
POKLeakageCurrent IPOK TA = +25°C, VPOK = 5.5V 0.1 1 μA
POKPropagationDelayTime tPOK FBforced50mVbeyondPOKtripthreshold 2μs
POKOutputLowVoltage ISINK = 3mA 100 mV
Overvoltage-FaultLatchDelay
Time
FBforced50mVabovePOKuppertrip
threshold 2μs
Undervoltage-FaultLatchDelay
Time
FBforced50mVbelowPOKlowertrip
threshold, TUV 1.6 ms
LOGIC INPUTS
ENInputHighThreshold Rising,hysteresis=215mV(typ) 1.0 1.4 1.6 V
ENInputLeakageCurrent TA = +25°C 0.1 1 μA
THERMAL SHUTDOWN
Thermal-Shutdown Threshold TSHDN Hysteresis = 15°C +160 °C
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
3
Electrical Characteristics (continued)
(VCC = 5V, VIN = 3.3V - 5V, VOUT=0.9V-3.3V,IOUT = 0–5A, TA = +25°C, unless otherwise noted.)
60
65
70
75
80
85
90
95
100
100 1000 10000
EFFICIENCY (%)
OUTPUT CURRENT (mA)
EFFICIENCY
vs. OUTPUT CURRENT
toc01
VIN = 3.3V
VCC = 5.0V
VOUT = 0.9V
VOUT = 1.2V
VOUT = 1.8V
VOUT = 2.5V
60
65
70
75
80
85
90
95
100
100 1000 10000
EFFICIENCY (%)
OUTPUT CURRENT (mA)
EFFICIENCY
vs. OUTPUT CURRENT
toc02
VIN = 5.0V
VCC = 5.0V
VOUT = 0.9V
VOUT = 1.2V
VOUT = 1.8V
VOUT = 2.5V VOUT = 3.3V
LOAD REGULATION
(VOUT = 0.75V)
MAXM17515 toc03
OUTPUT CURRENT (A)
VOUT (V)
4.54.00.5 1.0 1.5 2.5 3.02.0 3.5
0.740
0.745
0.750
0.755
0.760
0.765
0.770
0.775
0.735
0 5.0
VOUT = 0.75V
VCC = 5.0V
VIN = 5.0V
VIN = 3.3V
LOAD REGULATION
(VOUT = 1.2V)
MAXM17515 toc04
OUTPUT CURRENT (A)
VOUT (V)
4.54.03.53.02.52.01.51.00.5
1.15
1.16
1.17
1.18
1.19
1.20
1.21
1.14
0 5.0
VOUT = 1.2V
VCC = 5.0V
VIN = 5.0V
VIN = 3.3V
LOAD REGULATION
(VOUT = 1.8V)
MAXM17515 toc05
OUTPUT CURRENT (A)
VOUT (V)
4.54.03.0 3.51.0 1.5 2.0 2.50.5
1.74
1.75
1.76
1.77
1.78
1.79
1.80
1.81
1.82
1.83
1.73
0 5.0
VOUT = 1.8V
VCC = 5.0V
VIN = 5.0V
VIN = 3.3V
LOAD REGULATION
(VOUT = 2.5V)
MAXM17515 toc06
OUTPUT CURRENT (A)
VOUT (V)
4.54.03.53.02.52.01.51.00.5
2.40
2.42
2.44
2.46
2.48
2.50
2.52
2.38
0 5.0
VOUT = 2.5V
VCC = 5.0V
VIN = 5.0V
VIN = 3.3V
OUTPUT-VOLTAGE RIPPLE
(VIN = 5V, VOUT = 1.2V, IOUT = 5A)
MAXM17515 toc07
VOUT
10mV/div
(AC-COUPLED)
1µs/div
INPUT VOLTAGE RIPPLE
VIN = 5V, VOUT = 1.2V, IOUT = 5A
50mV/div
(AC-
COUPLED)
toc08
1µs/div
VIN
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
MaximIntegrated
│
4
www.maximintegrated.com
Typical Operating Characteristics
(VCC = 5V, VIN = 3.3V - 5V, VOUT=0.9V-3.3V,IOUT = 0–5A, TA = +25°C, unless otherwise noted.)
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 5.0V, VOUT = 1.2V, IOUT = 2.5 TO 5A)
MAXM17515 toc10
IOUT
VOUT
2A/div
50mV/div
(AC-COUPLED)
10µs/div
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 3.3V, VOUT = 2.5V, IOUT = 2.5 TO 5A)
MAXM17515 toc11
IOUT
VOUT
2A/div
50mV/div
(AC-COUPLED)
10µs/div
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 5.0V, VOUT = 2.5V, IOUT = 2.5 TO 5A)
MAXM17515 toc12
IOUT
VOUT
2A/div
50mV/div
(AC-COUPLED)
10µs/div
STARTUP WAVEFORM
(VIN = 3.3V, VOUT = 1.2V, IOUT = 0A)
MAXM17515 toc13
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 3.3V, VOUT = 1.2V, IOUT = 2.5 TO 5A)
MAXM17515 toc09
IOUT
VOUT
2A/div
50mV/div
(AC-COUPLED)
10µs/div
SHUTDOWN WAVEFORM
(VIN = 3.3V, VOUT = 1.2V, IOUT = 30mA)
MAXM17515 toc14
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
MaximIntegrated
│
5
www.maximintegrated.com
Typical Operating Characteristics (continued)
(VCC = 5V, VIN = 3.3V - 5V, VOUT=0.9V-3.3V,IOUT = 0–5A, TA = +25°C, unless otherwise noted.)
STARTUP WAVEFORM
(VIN = 3.3V, VOUT = 1.2V, IOUT = 5A)
MAXM17515 toc15
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
SHUTDOWN WAVEFORM
(VIN = 3.3V, VOUT = 1.2V, IOUT = 5A)
MAXM17515 toc16
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
STARTUP WAVEFORM
(VIN = 5.0V, VOUT = 1.2V, IOUT = 0A)
MAXM17515 toc17
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
SHUTDOWN WAVEFORM
(VIN = 5.0V, VOUT = 1.2V, IOUT = 30mA)
MAXM17515 toc18
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
STARTUP WAVEFORM
(VIN = 5.0V, VOUT = 1.2V, IOUT = 5A)
MAXM17515 toc19
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
SHUTDOWN WAVEFORM
(VIN = 5.0V, VOUT = 1.2V, IOUT = 5A)
MAXM17515 toc20
VLX
VEN
VOUT
VPOK
5V/div
5V/div
2V/div
500mV/div
400µs/div
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
MaximIntegrated
│
6
www.maximintegrated.com
Typical Operating Characteristics (continued)
(VCC = 5V, VIN = 3.3V - 5V, VOUT=0.9V-3.3V,IOUT = 0–5A, TA = +25°C, unless otherwise noted.)
LOAD SHORT-CIRCUIT
(VIN = 5.0V, VOUT = 1.2V, IOUT = 0A)
MAXM17515 toc21
IOUT
VOUT
VPOK
VLX
5A/div
5V/div
1V/div
2V/div
400µs/div
LOAD SHORT-CIRCUIT
(VIN = 5.0V, VOUT = 1.2V, IOUT = 5A)
MAXM17515 toc22
IOUT
VOUT
VPOK
VLX
5A/div
5V/div
1V/div
2V/div
400µs/div
MAXM17515 toc23
AMBIENT TEMPERATURE (°C)
OUTPUT CURRENT (A)
11010090807060
1
2
3
4
5
6
0
50 120
VOUT = 3.3V
VOUT = 1.8V
VOUT = 1.1V
OUTPUT CURRENT
vs. AMBIENT TEMPERATURE
(VIN = 5.0V NO AIR FLOW)
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
MaximIntegrated
│
7
www.maximintegrated.com
Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1–3,
28 IN InputSupplyConnection.BypasstoGNDwitha22µFor2x10µFceramiccapacitor.Supplyrangeforthis
pinis4.5Vto5.5V.WhenVCCcanbesuppliedseparatelyfroma4.5Vto5.5Vsource,theINpincanthenbe
powered from a 2.4V to 5.5V supply.
4POK Open-DrainPower-GoodOutput.POKispulledlowifFBismorethan12%(typ)aboveorbelowthenominal
regulationthreshold.POKisheldlowinshutdown.POKbecomeshighimpedancewhenFBisinregulation
range.Pullthispinupwith10kΩ(typ)resistorvalue.
5–7 GND GND.ConnectPGNDandGNDtogetheratasinglepoint.
8 VCC
5VBiasSupplyInputfortheInternalSwitchingRegulatorDrivers.ForINfrom4.5Vto5.5V,VCC can be
connectedtotheINsupply.ForINsupplyvoltageslowerthantheaboverange,VCC should be powered from
a separate 5V ±10% supply and bypassed with a 1µF or greater ceramic capacitor.
9FB FeedbackInputfortheInternalStep-DownConverter.ConnectFBtoaresistivedividerbetweenOUTand
GNDtoadjustthetypicaloutputvoltagebetween0.765Vto3.6V.Keepequivalentdividerresistancelower
than50kΩ.
10 EN RegulatorEnableInput.WhenENispulledlow,theregulatorisdisabled.WhenENisdrivenhigh,the
regulator is enabled.
11, 12 N.C. No Connection
13–20 OUT RegulatorOutputPins.ConnectanoutputcapacitorbetweenOUTandPGNDwitha220µF(typ)POSCAP
low-ESRcapacitor.
21–27 PGND PowerGNDReturn.ConnecttoGND.
— EP1 ExposedPad1.ConnectthispadtothePGNDgroundplaneof1inby1incopperforcooling.
— EP2 ExposedPad2.ConnectthispadtothePCBforbetterthermalperformance,butdonotconnecttoanyothernode.
Minimizeareaofcopperisland.
— EP3 Exposed Pad 3. Connect this pad to the OUT pins and the copper area of 1in by 1in.
56 7 8 9 10 11 12 13 14
POK
GND
GND
GND
V
C C
FB
E N
N.C.
N.C.
O U T
O U T
OUT
OUT
OUT
OUT
O U T
O U T
PGND
PGND
PGND
PGND
PGND
PGND
PGND
IN
19
2021
22
23
242526
27
28
415
IN
IN
IN
1
2
3
16
17
18
MAXM17515
EP 2
EP 1 EP 3
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
8
Pin Description
Pin Conguration
OUT
IN
PGND
FB
POK
EN
V
CC
GND
1µH
2.2µF
2.2µF
0.1µF
MAXM17515
POK
LOGIC
CURRENT MODE
CONTROLLER
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
9
Functional Diagram
Design Procedure
Adjusting Output Voltage
TheMAXM17515producesanadjustable0.75Vto3.6V
output voltage from a 2.4V to 5.5V input voltage range by
usingaresistivefeedbackdividerfromOUTtoFB.The
device can deliver up to 5A output current up to an output
voltage of 2.5V at +70°C. The output current derates for
output voltages above 2.5V.
Adjustingtheoutputvoltageofthedevicerequiresaresis-
tive divider network from OUT to FB, according to the
equation below. From the initial output voltage, the load-
line regulation reduces the effective feedback voltage by
a typical 5mV/A as the output current increases.
OUT
UB
V
RR 1
0.765
kΩ,whereRBisinkΩ.
Input Voltage Range
The maximum value (VIN(MAX)) and minimum value
(VIN(MIN)) must accommodate the worst-case conditions
accountingfortheinputvoltagesoarsanddrops.Ifthere
is a choice at all, lower input voltages result in better
efficiency.Withamaximumdutycycleof87.5%,VOUT is
limited to 0.875 x VIN.
Input Capacitor Selection
The input capacitor must meet the ripple-current require-
ment(IRMS)imposedbytheswitchingcurrents.TheIRMS
requirements of the regulator can be determined by the
following equation:
RMS OUT
I I D (1 D)= × ×−
The worst-case RMS current requirement occurs when
operatingwithD=0.5.Atthispoint,theaboveequation
simplifiestoIRMS=0.5xIOUT.
The minimum input capacitor required can be calculated
by the following equation:
( )
( )
IN_AVG
IN IN SW
I (1 D)
CVf
×−
=∆×
where:
IIN_AVGis the average input current given by:
OUT
IN_Avg
IN
P
IV
=η×
D is the operating duty cycle, which is approximately
equal to VOUT/VINwhere:
∆VIN is the required input-voltage ripple,
fSW is the operating switching frequency,
POUT is the output power, which is equal to VOUTxIOUT,
ηistheefficiency.
For the device’s system (IN) supply, ceramic capaci-
tors are preferred due to their resilience to inrush surge
currents typical of systems, and due to their low parasitic
inductance, which helps reduce the high-frequency ring-
ing on the IN supply when the internal MOSFETs are
turned off. Choose an input capacitor that exhibits less
than+10°CtemperatureriseattheRMSinputcurrentfor
optimal circuit longevity.
Output Capacitor Selection
The output capacitor selection requires careful evalua-
tion of several different design requirements (e.g., stabil-
ity, transient response, and output ripple voltage) that
place limits on the output capacitance and the effective
series resistance (ESR). Based on these requirements,
acombinationoflow-ESRpolymercapacitors(lowercost
but higher output ripple voltage) and ceramic capacitors
(higher cost but low output ripple voltage) should be used
to achieve stability with low output ripple.
Loop Compensation
The gain portion of the loop gain is a result of error-
amplifier gain, current-sensing gain, and load with an
overall typical value at 1kHz of 36dB at VIN = 5V, and
46dBatVIN = 3V, with a typical limit to the gain-bandwidth
(GBW)productof120,000.Thecrossovershouldoccur
before this error-amplifier bandwidth limit of 120kHz
(gain = 1). The output capacitor and load introduces a
pole with the worst case at the maximum load (5A). If
the load pole location is further than a frequency where
thegainexceedstheGBW,thegaindropstartsearlierat
Figure 1. Adjusting Output Voltage
OUT
MAXM17515
V
OUT
FB
R
U
R
B
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
10
the location where the loop gain is limited. This situation
applies typically to an output voltage less than 1.8V, so
zerofrequencyfromtheESRisneededtoincreasethe
phase margin at the crossover frequency.
The recommended relationship between ESR and total
output capacitance values are shown in Table 1.Whena
low-ESRtypecapacitorisusedwithaceramiccapacitor,
a recommended value of 44µF to 100µF ceramic capaci-
tor should be used to make up the total capacitance value
withtherelationshipbetweenESRandtotaloutputcapac-
itance value, such that the zero frequency is between
32kHzand40kHz.Whenonlyalow-ESRtypecapacitor
isused,thezerofrequencyshouldbebetween62kHzand
80kHz.Optionally,asmall10µF–22µFceramiccapacitor
can be used to reduce output ripple.
Optionally, for an output greater than or equal to 1.8V,
an all-ceramic capacitor solution can be used with a
minimum capacitance value that locates the pole location
below1kHzwithresistiveload(5A),andwithasimplified
equation given by COUTMIN (µF) = 900/VOUT.
Output Ripple Voltage
Withpolymercapacitors,theESRdominatesanddeter-
mines the output ripple voltage. The step-down regulator’s
output ripple voltage (VRIPPLE) equals the total inductor
ripple current (ΔIL) multiplied by the output capacitor’s
ESR. Therefore, the maximum ESR to meet the output
ripple-voltage requirement is:
RIPPLE
ESR
L
V
RI
≤∆
where:
IN OUT OUT
LIN SW
VV V 1
IL Vf

−

∆= × ×




where fSWistheswitchingfrequencyandListheinduc-
tor (1µH).
The actual capacitance value required relates to the
physicalcase sizeneeded toachievethe ESRrequire-
ment, as well as to the capacitor chemistry. Thus, polymer
capacitorselectionisusuallylimitedbyESRandvoltage
rating rather than by capacitance value.
Withceramiccapacitors,theripplevoltageduetocapaci-
tance dominates the output ripple voltage. Therefore,
the minimum capacitance needed with ceramic output
capacitors is:
OUT SW
L
RIPPLE
I1
C8f V

∆
= ×

×

Alternatively,combiningceramics(forthelowESR)and
polymers (for the bulk capacitance) helps balance the out-
put capacitance vs. output ripple-voltage requirements.
Load-Transient Response
The load-transient response depends on the overall out-
put impedance over frequency, and the overall amplitude
andslewrateoftheloadstep.Inapplicationswithlarge,
fast-load transients (load step > 80% of full load and slew
rate > 10A/μs), the output capacitor’s high-frequency
response (ESL and ESR) needs to be considered. To
prevent the output voltage from spiking too low under a
load-transientevent,theESRislimitedbythefollowing
equation (ignoring the sag due to finite capacitance):
RIPPLESTEP
ESR
OUTSTEP
V
RI
≤∆
where VRIPPLESTEP is the allowed voltage drop during
load current transient, and IOUTSTEP is the maximum
load current step.
The capacitance value dominates the mid-frequency
output impedance and continues to dominate the load-
transient response as long as the load transient’s slew
rate is fewer than two switching cycles. Under these
Table 1. Output Capacitor Selection vs. ESR
TOTAL COUT (µF) LOW-ESR TYPE WITH CERAMIC-TYPE
ESR (mΩ)
LOW-ESR TYPE WITHOUT CERAMIC-TYPE
ESR (mΩ)
250 16–20 8–10
300 13–17 7–9
350 11–14 6, 7
400 10–12 5, 6
450 9–11 4–6
500 8–10 4, 5
550 7–9 4, 5
600 7, 8 3, 4
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
11
Idle Mode is a trademark of Maxim Integrated Products, Inc
conditions, the sag and soar voltages depend on the
output capacitance, inductance value, and delays in the
transientresponse.Lowinductorvaluesallowtheinductor
current to slew faster, replenishing charge removed from
or added to the output filter capacitors by a sudden load
step, especially with low differential voltages across the
inductor. The minimum capacitance needed to handle the
sag voltage (VSAG) that occurs after applying the load
current can be estimated by the following equation:
( )
( )
OUT_SAG SAG
2
STEP STEP sw
MAX
1
CV
L IOUT
1IOUT (t T)
2 VIN D VOUT
= ×


×∆


+ ∆ × −∆

×−



where:
D
MAX is the maximum duty factor (87.5%),
tSW is the switching period (1/fSW),
ΔT equals VOUT/VIN x tSW when in PWM mode, or
LxIIDLE/(VIN - VOUT)wheninIdleMode(1.5A).
The minimum capacitance needed to handle the over-
shoot voltage (VSOAR) that occurs after load removal
(due to stored inductor energy) can be calculated as:
( )
2
STEP
OUT_SOAR OUT SOAR
IOUT L
C2V V
∆
≈
When the device is operating under low duty cycle,
the output capacitor size is usually determined by the
COUT_SOAR.
Detailed Description
The MAXM17515 is a complete step-down switch-mode
power-supply solution that can deliver up to 5A output
current and up to 3.6V output voltage from a 2.4V to 5.5V
input voltage range. The device includes switch-mode
power-supply controller, dual n-channel MOSFET power
switches, and an inductor. The device uses a fixed-fre-
quency current-mode control scheme.
The device provides peak current-limit protection, output
undervoltage protection, output overvoltage protection,
and thermal protection. The device operates in skip
mode at light loads to improve the light-load efficiency.
Independentenableandanopen-drainpower-goodout-
put allow flexible system power sequencing. The fixed
voltage soft-start reduces the inrush current by gradually
ramping up the internal reference voltage.
Fixed-Frequency Current-Mode Controller
The heart of the current-mode PWM controller is a
multistage, open-loop comparator that compares the
output voltage-error signal with respect to the reference
voltage, the current-sense signal, and the slope-compen-
sation ramp (see the Functional Diagram). The device
uses a direct summing configuration, approaching ideal
cycle-to-cycle control over the output voltage without a
traditional error amplifier and the phase shift associated
with it.
Light-Load Operation
The device features an inherent automatic switchover
to pulse skipping (PFM operation) at light loads. 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 during the off-time. Once the current
through the low-side MOSFET drops below the zero-
crossing trip level, it turns off the low-side MOSFET. This
prevents the inductor from discharging the output capaci-
tors and forces the switching regulator to skip pulses
under light-load conditions to avoid overcharging the
output. Therefore, the controller regulates the valley of the
output ripple under light-load conditions. The switching
waveforms can appear noisy and asynchronous at light-
load pulse-skipping operation, but this is a normal operat-
ing condition that results in high light-load efficiency.
Idle Mode™ Current-Sense Threshold
InIdleMode,theon-timeofthestep-downcontrollerter-
minates when both the output voltage exceeds the feed-
back threshold, and the internal current-sense voltage
fallsbelowtheIdleModecurrent-sensethreshold(IIDLE =
1.5A). Another on-time cannot be initiated until the output
voltagedropsbelowthefeedbackthreshold.Inthismode,
thebehaviorappearslikePWMoperationwithoccasional
pulse skipping, where inductor current does not need to
reach the light-load level.
Power-On Reset (POR) and UVLO
Power-on reset (POR) occurs when VCC rises above
approximately 2.1V, resetting the undervoltage, over-
voltage, and thermal-shutdown fault latches. The VCC
inputundervoltage-lockout(UVLO)circuitrypreventsthe
switching regulators from operating if the 5V bias supply
(VCC)isbelowits4VUVLOthreshold.
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
12
Soft-Start
The internal step-down controller starts switching and
theoutputvoltagerampsupusingsoft-start.Ifthe VCC
biassupplyvoltagedropsbelowtheUVLOthreshold,the
controller stops switching and disables the drivers (LX
becomes high impedance) until the bias supply voltage
recovers.
Once the 5V VCC bias supply and VIN rise above their
respectiveinputUVLOthresholds,andENispulledhigh,
the internal step-down controller becomes enabled and
begins switching. The internal voltage soft-starts gradu-
ally increment the feedback voltage by approximately
25mV every 61 switching cycles, making the output volt-
age reach its nominal regulation voltage 1.79ms after the
regulatorisenabled(seetheSoft-StartWaveformsinthe
Typical Operating Characteristics section).
Power-Good Output (POK)
POKistheopen-drainoutputofthewindowcomparator
that continuously monitors the output for undervoltage
and overvoltage conditions. POK is actively held low in
shutdown (EN = GND). POK becomes high impedance
after the device is enabled and the output remains within
±10%ofthenominalregulationvoltagesetbyFB.POK
goes low once the output drops 12% (typ) below or rises
12% (typ) above its nominal regulation point, or the output
shuts down. For a logic-level POK output voltage, con-
nectanexternalpullupresistorbetweenPOKandVCC. A
10kΩpullupresistorworkswellinmostapplications.
Output Overvoltage Protection (OVP)
If the output voltage rises to 112% (typ) of its nominal
regulation voltage, the controller sets the fault latch, pulls
POK low, shuts down the regulator, and immediately
pulls the output to ground through its low-side MOSFET.
Turning on the low-side MOSFET with 100% duty cycle
rapidly discharges the output capacitors and clamps the
output to ground. However, this commonly undamped
response causes negative output voltages due to the
energystoredintheoutputLCattheinstantof0Vfault.If
the load cannot tolerate a negative voltage, place a power
Schottky diode across the output to act as a reverse-
polarityclamp.Iftheconditionthatcausedtheovervolt-
age persists (such as a shorted high-side MOSFET),
the input source also fails (short-circuit fault). Cycle VCC
below 1V or toggle the enable input to clear the fault latch
and restart the regulator.
Output Undervoltage Protection (UVP)
The device includes an output undervoltage-protection
(UVP) circuit that begins to monitor the output once the
startupblankingperiodhasended.Iftheoutputvoltage
drops below 88% (typ) of its nominal regulation voltage,
the regulator pulls the POK output low and begins the
UVP fault timer. Once the timer expires after 1.6ms, the
regulator shuts down, forcing the high-side MOSFET
off and disabling the low-side MOSFET once the zero-
crossing threshold has been reached. Cycle VCC below
1V, or toggle the enable input to clear the fault latch and
restart the regulator.
Thermal-Fault Protection
The device features a thermal-fault protection circuit.
Whenthejunctiontemperaturerisesabove+160°C(typ),
a thermal sensor activates the fault latch, pulls down the
POKoutput,andshutsdowntheregulator.ToggleENto
clear the fault latch, and restart the controllers after the
junctiontemperaturecoolsby15°C(typ).
Power Dissipation
The device output current needs to be derated if the out-
put voltage is above 2.5V or if the device needs to oper-
ate in high ambient temperature. The amount of current
derating depends upon the input voltage, output voltage,
and ambient temperature. The derating curves given in
the Typical Operating Characteristics section can be used
as a guide.
The maximum allowable power losses can be calculated
using the following equation:
JMAX A
MAX
JA
TT
PD
−
=q
where:
PDMAX is the maximum allowed power losses with
maximumallowedjunctiontemperature,
TJMAXisthemaximumallowedjunctiontemperature,
TA is operating ambient temperature,
qJAisthejunction-to-ambientthermalresistance.
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
13
PCB Layout Guidelines
CarefulPCBlayoutiscriticaltoachievinglowswitching
losses and clean, stable operation. Use the following
guidelinesforgoodPCBlayout:
● Keeptheinputcapacitorsascloseaspossibletothe
INandPGNDpins.
● Keeptheoutputcapacitorsascloseaspossibleto
theOUTandPGNDpins.
● ConnectallthePGNDconnectionstoaslargea
copper plane area as possible on the top layer.
● ConnectEP1tothePGNDandGNDplanesonthe
top layer.
● UsemultipleviastoconnectinternalPGNDplanesto
thetop-layerPGNDplane.
● DonotkeepanysoldermaskonEP1–EP3onbot-
tomlayer.Keepingsoldermaskonexposedpads
decreases the heat-dissipating capability.
● Keepthepowertracesandloadconnectionsshort.
This practice is essential for high efficiency. Using
thickcopperPCBs(2ozvs.1oz)canenhancefull-
loadefficiency.CorrectlyroutingPCBtracesisa
difficult task that must be approached in terms of
fractions of centimeters, where a single milliohm of
excess trace resistance causes a measurable
efficiency penalty. Figure 2. Layout Recommendation
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
PART TEMP RANGE MSL PIN-PACKAGE
MAXM17515ALI+T -40°C to +125°C 3 28 SiP
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
28 SiP L286510+1 21-0701 90-0445
V
OUT
56 7 8 10 11 12 13 14
2021
22
23
242526
27
28
415
1
2
316
17
18
EP2EP1 EP3
V
V
OUT
Figure 2
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
www.maximintegrated.com MaximIntegrated
│
14
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
thata“+”,“#”,or“-”inthepackagecodeindicatesRoHSstatus
only. Package drawings may show a different suffix character, but
thedrawingpertainstothepackageregardlessofRoHSstatus.
Chip Information
PROCESS:BiCMOS
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 11/14 Initialrelease —
1 4/15 TightenedFBaccuracyandaddedMSL3rating 2, 14
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAXM17515 5A, 2.4V to 5.5V Input,
High-Efciency Power Module
© 2014 MaximIntegratedProducts,Inc.
│
15
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.