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MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorTypical Operating Characteristics (continued)(VIN VEN/UVLO 24V, VSGND VPGND 0V, TA -40 C to 125 C, unless otherwise noted. Typical values are at TA 25 C. Allvoltages are referenced to GND, unless otherwise noted. The circuit values for different output-voltage applications are as in Table 1,unless otherwise noted.)toc1924.8POWER-UP AND DOWN THROUGH EN/UVLO(VIN 24V, VOUT 12V, IOUT 25mAPFM MODE, MODE OPEN)toc21POWER-UP AND DOWN THROUGH EN/UVLO(VIN 24V, VOUT 12V, IOUT 3APWM MODE, MODE SGND) toc20OUTPUT VOLTAGE vs. LOAD CURRENT(24V OUTPUT, PFM MODE, fSW 1MHz)24.7VEN/UVLOOUTPUT VOLTAGE (V)24.65V/divVEN/UVLO5V/div24.524.4VIN 48V24.324.1VIN 10V/divVRESET5V/divVRESETVIN 60V24.2110100LOAD CURRENT (mA)POWER-UP WITH 5V BIAS(VIN 24V, VOUT 12V, IOUT 0APWM MODE, MODE SGND)1000LOAD TRANSIENT(VIN 24V, VOUT 12V, IOUT 0A TO 1.5APWM MODE, MODE SGND)toc23toc225V/div4ms/div4ms/divLOAD TRANSIENT(VIN 24V, VOUT 12V, IOUT 1.5A TO 3APWM MODE, MODE vLOAD TRANSIENT(VIN 24V, VOUT 15V, IOUT 0A TO 1.5APWM MODE, MODE SGND)toc25LOAD TRANSIENT(VIN 24V, VOUT 15V, IOUT 1.5A TO 3APWM MODE, MODE SGND)toc26LOAD TRANSIENT(VIN 48V, VOUT 24V, IOUT 0A TO 1.5APWM MODE, MODE A/div400µs/divMaxim Integrated 8

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorTypical Operating Characteristics (continued)(VIN VEN/UVLO 24V, VSGND VPGND 0V, TA -40 C to 125 C, unless otherwise noted. Typical values are at TA 25 C. Allvoltages are referenced to GND, unless otherwise noted. The circuit values for different output-voltage applications are as in Table 1,unless otherwise noted.)LOAD TRANSIENT(VIN 48V, VOUT 24V, IOUT 1.5A TO 3APWM MODE, MODE SGND)toc28VOUTIOUTLOAD TRANSIENT(VIN 24V, VOUT 12V, IOUT 25mA TO 1.5ADCM MODE, MODE VCC)toc29200mV/div(ACCOUPLED)VOUT1A/divIOUTOUTPUT SHORT IN STEADY-STATE(VIN 24V, VOUT 12V, OUTPUT SHORTPWM MODE, MODE SGND)toc31LOAD TRANSIENT(VIN 24V, VOUT 12V, IOUT 25mA TO 1.5APFM MODE, MODE OUTVLX20V/divIOUT5A/div20ms/div1ms/divSTARTUP INTO SHORT(VIN 24V, VOUT 12V, OUTPUT SHORTPWM MODE, MODE SGND)toc32SYNC FREQUENCY AT 840KHZ(VIN 24V, VOUT 12V, IOUT 3APWM MODE, MODE LED)4µs/divMaxim Integrated 9

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorTypical Operating Characteristics (continued)(VIN VEN/UVLO 24V, VSGND VPGND 0V, TA -40 C to 125 C, unless otherwise noted. Typical values are at TA 25 C. Allvoltages are referenced to GND, unless otherwise noted. The circuit values for different output-voltage applications are as in Table 1,unless otherwise noted.)BODE PLOT(VIN 24V, VOUT 12V, IOUT 3A)80PHASE103104FREQUENCY (Hz)BODE PLOT(VIN 48V, VOUT 24V, IOUT 3A)120404020-20-40-4020GAIN0-20fCR 38.3kHz,PHASE MARGIN 61.8 103104FREQUENCY (Hz)105-40toc374.01201003.5VIN 24V, VOUT 12V6040402020GAIN00OUTPUT CURRENT (A)8060-4060OUTPUT CURRENTvs. AMBIENT 0GAIN (dB)0fCR 33.8kHz,PHASE MARGIN 60.8 toc3580PHASE( )20GAIN0GAIN (dB)1004020-40806040-20120PHASE( )GAIN (dB)60100PHASE( )toc34100BODE PLOT(VIN 24V, VOUT 15V, IOUT 3A)3.02.5VIN 24V, VOUT 12VVIN 48V, VOUT 12V2.0VIN 48V, VOUT 15V1.5-20fCR 40.0kHz,PHASE MARGIN 64.0 103www.maximintegrated.com104FREQUENCY (Hz)105-40VIN 48V, VOUT 24V1.0020406080100120AMBIENT TEMPERATURE ( C)Maxim Integrated 10

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorPin ConfigurationMODE/SYNCINPGNDDLOUT2625OUT N SiP9mm x 15mm x 4.32mmwww.maximintegrated.comMaxim Integrated 11

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorPin DescriptionPINNAMEFUNCTION1VCC5V LDO Output. The VCC is bypassed to PGND internally through a 2.2µF capacitor. Do not connect anyexternal components to the VCC pin.2RESETOpen-Drain RESET Output. The RESET output is driven low if FB drops below 92.5% of its set value.RESET goes high 1024 clock cycles after FB rises above 95.5% of its set value. See the RESET Outputsection for more details.3RT4SGND5CFCompensation Pin. Connect a 2.2pF capacitor from CF to FB.6FBFeedback Input. Connect FB to the center tap of an external resistor-divider from the OUT to SGND toset the output voltage.7SSSoft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time.8EN/UVLO9, 28IN10, 14-21,27PGND11EXTVCCExternal Power Supply Input for the Internal LDO. Applying a voltage between 4.7V and 24V at theEXTVCC pin bypasses the internal LDO and improves efficiency.12BSTBoost Flying Capacitor Node. Internally a 0.1μF is connected from BST to LX. Do not connect anyexternal components to the BST pin.13LX22-25OUT26DLSwitching Frequency Programming Pin. Connect a resistor from RT to SGND to set the regulator'sswitching frequency. Leave RT open for the default 450kHz frequency. See the Setting the SwitchingFrequency (RT) section for more details.Analog Ground.Enable/Undervoltage-Lockout Input. Connect a resistor from EN/UVLO to SGND to set the UVLOthreshold. By default, the module is enabled with the EN/UVLO pin open.Power-Supply Input. Decouple to PGND with a capacitor; place the capacitor close to the IN and PGNDpins.Power Ground.Switching Node. Leave unconnected; do not connect any external components to the LX pin.Regulator Output Pin. Connect a capacitor from OUT to PGND.Gate Drive for Low-Side MOSFET. Do not connect any external components to the DL pin.29MODE/SYNCPWM/PFM/DCM Mode-Selection Input. MODE pin configures the module to operate in PWM, PFM, orDCM modes of operation. Leave MODE unconnected for PFM operation (pulse skipping at light loads).Connect MODE to SGND for constant frequency PWM operation at all loads. Connect MODE to VCC forDCM operation. The device can be synchronized to an external clock using this pin. See the Mode Selection (MODE) and External Frequency Synchronization sections for more details.EP1, EP2,EP3—Exposed Pad. Create a large copper plane below the module connecting EP1, EP2, and EP3 to improveheat dissipation capability. PGND and SGND are shorted through this plane.www.maximintegrated.comMaxim Integrated 12

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorFunctional NT DESELECTIONLOGICERROR AMPLIFIER/LOOP /SYNCRESETLOGICMaxim Integrated 13

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorDetailed DescriptionThe MAXM17537 is a high-efficiency, high-voltage,synchronous step-down module with dual-integratedMOSFETs that operates over a 4.5V to 60V input, andsupports a programmable output voltage from 8V to 24V,delivering up to 3A current. Built-in compensation for theentire output-voltage range eliminates the need for external components. The feedback (FB) regulation accuracyover -40 C to 125 C is 1.5%.The device features a peak-current-mode control architecture. An internal transconductance-error amplifier produces an integrated error voltage at an internal node thatsets the duty cycle using a PWM comparator, a high-sidecurrent-sense amplifier, and a slope-compensation generator. At each rising edge of the clock, the high-sideMOSFET turns on and remains on until either the appropriate or maximum duty cycle is reached, or the peakcurrent limit is detected. During the high-side MOSFET’son-time, the inductor current ramps up. During the secondhalf of the switching cycle, the high-side MOSFET turnsoff and the low-side MOSFET turns on. The inductorreleases the stored energy as its current ramps downand provides current to the output. The device features aMODE/SYNC pin that can be used to operate the devicein PWM, PFM, or DCM control schemes and to synchronize the switching frequency to an external clock. Thedevice integrates adjustable-input undervoltage lockout,adjustable soft-start, open-drain RESET, auxiliary bootstrap LDO, and DL-to-OUT short-detection features.Mode Selection (MODE)The logic state of the MODE/SYNC pin is latched whenVCC and EN/UVLO voltages exceed the respective UVLOrising thresholds and all internal voltages are ready toallow LX switching. If the MODE/SYNC pin is open atpower-up, the device operates in PFM mode at lightloads. If the MODE/SYNC pin is grounded at power-up,the device operates in constant-frequency PWM modeat all loads. Finally, if the MODE/SYNC pin is connectedto VCC at power-up, the device operates in constant frequency DCM mode at light loads. State changes on theMODE/SYNC pin are ignored during normal operation.PWM Mode OperationIn PWM mode, the inductor current is allowed to go negative. PWM operation provides constant frequency operation at all loads, and is useful in applications sensitiveto changes in switching frequency. However, the PWMmode of operation gives lower efficiency at light loadscompared to PFM and DCM modes of operation.www.maximintegrated.comPFM Mode OperationThe PFM mode of operation disables negative inductorcurrent and additionally skips pulses at light loads for highefficiency. In PFM mode, the inductor current is forced toa fixed peak of 2A (typ) every clock cycle until the outputrises to 102.3% of the nominal voltage. Once the outputreaches 102.3% of the nominal voltage, both the highside and low-side FETs are turned off and the deviceenters hibernation mode until the load discharges theoutput to 101.1% of the nominal voltage. Most of the internal blocks are turned off in hibernation mode to minimizequiescent current. After the output falls below 101.1% ofthe nominal voltage, the device comes out of hibernationmode, turns on all internal blocks, and again commencesthe process of delivering pulses of energy to the outputuntil it reaches 102.3% of the nominal output voltage. Theadvantage of the PFM mode is higher efficiency at lightloads because of lower quiescent current drawn from thesupply. The disadvantage is that the output-voltage rippleis higher compared to PWM or DCM modes of operationand switching frequency is not constant at light loads.DCM Mode OperationDCM mode of operation features constant frequencyoperation down to lighter loads than PFM mode by notskipping pulses, but only disabling negative inductor current at light loads. DCM operation offers efficiency performance that lies between PWM and PFM modesLinear RegulatorThe MAXM17537 has two internal low-dropout (LDO)regulators that power VCC. During power-up, whenthe EN/UVLO pin voltage is above the true shutdownvoltage (0.8V), then the VCC is powered from INLDO.When VCC voltage is above the VCC UVLO thresholdand EXTVCC voltage is greater than 4.7V (typ), theVCC is powered from EXTVCC LDO. Only one of the twoLDOs is in operation at a time depending on the voltagelevel present at EXTVCC. Powering VCC from EXTVCCincreases efficiency at higher input voltages. EXTVCCvoltage should not exceed 24V.Typical VCC output voltage is 5V. Internally VCC isbypassed with a 2.2μF ceramic capacitor to PGND. Seethe Electrical Characteristics table for the current limitdetails for both the regulators. In applications where thebuck converter output is connected to the EXTVCC pin,if the output is shorted to ground, then the transfer fromEXTVCC LDO to INLDO happens seamlessly without anyimpact on the normal functionality.Maxim Integrated 14

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with Integrated InductorSetting the Switching Frequency (RT)The switching frequency of the MAXM17537 can be programmed from 100kHz to 2.2MHz by using a resistor connected from RT to SGND. The switching frequency (fSW)is related to the resistor connected at the RT pin (RRT) bythe following equation:R RT 19 10 3 1.7f SWwhere RRT is in kΩ and fSW is in kHz. Leaving the RTpin unconnected causes the device to operate at thedefault switching frequency of 450kHz. See the ElectricalCharacteristics table for RT resistor value recommendations for a few common frequencies.Operating Input Voltage RangeThe minimum and maximum operating input voltages fora given output voltage should be calculated as follows:VIN(MIN) VOUT I OUT(MAX) 0.091(1 f SW(MAX) 230 10 9VIN(MAX))() I OUT(MAX) 0.034VOUT f SW(MAX) t ON(MIN)where,VOUT Steady-state output voltage,IOUT(MAX) Maximum load current,fSW(MAX) Maximum switching frequency,tON(MIN) Worst-case minimum switch on-time (160ns).Also, for duty cycle 0.5;()VIN(MIN) (3.47 VOUT ) 5.36 10 5 f SW 0.936where fSW is the switching frequency in Hz.The component selection table, Table 1 provides theoperating input-voltage range and the optimum switchingfrequency range for the different selected output voltages.External Frequency Synchronizationlator frequency changes to the external clock frequency(from the original frequency based on the RT setting)after detecting 16 external clock edges. The converteroperates in PWM mode during synchronization operation. When the external clock is applied to the MODE/SYNC pin, the mode of operation changes to PWM fromthe initial state of PFM/DCM. When the external clock isremoved on-the-fly, then the internal oscillator frequencychanges to the RT set frequency and the converter stillcontinues to operate in PWM mode. The minimum external clock high pulse width should be greater than 50ns.See the MODE/SYNC pin description in the ElectricalCharacteristics table for details.DL-to-OUT Short DetectionIn the MAXM17537, the DL and OUT pins are adjacentto each other. To prevent damage to the low-side FET incase the DL pin is shorted to the OUT pins, the DL-toOUT short-detection feature has been implemented. If theMAXM17537 detects that the DL pin is shorted to the OUTpins before startup, the startup sequence is not initiatedand the output voltage is not soft-started.Overcurrent Protection (OCP)/HICCUP ModeThe MAXM17537 is provided with a robust overcurrentprotection (OCP) scheme that protects the modules underoverload and output short-circuit conditions. A cycle-bycycle peak current limit turns off the high-side MOSFETwhenever the high-side switch current exceeds an internal limit of 5.7A (typ). The module enters hiccup mode ofoperation either if one occurrence of the runaway currentlimit 6.7A (typ) is reached, or if the FB node goes below64.5% of its nominal regulation threshold after soft-startis complete. In hiccup mode, the module is protectedby suspending switching for a hiccup timeout period of32,768 switching cycles. Once the hiccup timeout periodexpires, soft-start is attempted again. Hiccup mode ofoperation ensures low power dissipation under outputoverload or short-circuit conditions. Note that when softstart is attempted under overload conditions, if feedbackvoltage does not exceed 64.5% of desired output voltage,the device switches at half the programmed switchingfrequency.The MAXM17537 is designed to support a maximum loadcurrent of 3A. The inductor ripple current is calculated asfollows:The internal oscillator of the MAXM17537 can be synchronized to an external clock signal on the MODE/SYNCpin. The external synchronization clock frequency mustVIN VOUT 0.111 I OUT VOUT 0.091 I OUT I be between 1.1 x fSW and 1.4 x fSW, where fSW is the freL f SW VIN 0.02 I OUT quency programmed by the RT resistor. When an externalclock is applied to the MODE/SYNC pin, the internal oscil-www.maximintegrated.comMaxim Integrated 15

MAXM175374.5V to 60V, 3A High-Efficiency, DC-DC Step-DownSiP Power Module with

a low-profile, thermally-efficient system-in-package (SiP). The device operates over a wide input-voltage range of 4.5V to 60V and delivers up to 3A continuous output cur-rent with excellent line and load regulation over an output-voltage range of 8V to 24V. The high level of integration significantly reduces design complexity and manufactur-