LTM4643 datasheet(10/30 Pages) AD

10 / 30 page

LTM4638

Rev. C

For more information www.analog.com

OPERATION

The LTM4638 is a standalone nonisolated switch mode

DC/DC power supply. It can deliver up to 15A DC output

current with few external input and output capacitors.

This module provides precisely regulated output voltage

adjustable between 0.6V to 5.5V via one external resistor

over a 3.1V to 20V input voltage range. The typical ap-

plication schematic is shown in Figure 23.

The LTM4638 contains an integrated constant on-time

valley current mode regulator, power MOSFETs, inductor,

and other supporting discrete components. The default

switching frequency is 600kHz. For switching noise-

sensitive applications, the switching frequency can be

adjusted by external resistors and the μModule regulator

can be externally synchronized to a clock within ±30% of

thesetfrequency.SeetheApplicationsInformationsection.

With current mode control and internal feedback loop

compensation, the LTM4638 module has sufficient stabil-

ity margins and good transient performance with a wide

range of output capacitors, even with all ceramic output

capacitors.

Current mode control provides cycle-by-cycle fast current

limiting. Internal output overvoltage and undervoltage

comparators pull the open-drain PGOOD output low if the

output feedback voltage exits a ±8% window around the

regulationpoint.ContinuousoperationisforcedduringOV

and UV condition except during start-up when the TRACK

pin is ramping up to 0.6V.

Furthermore,inordertoprotecttheinternalpowerMOSFET

devices against transient voltage spikes, the LTM4638

constantly monitors the VIN pin for an overvoltage condi-

tion. When VIN rises above 24.5V, the regulator suspends

operation by shutting off both power MOSFETs. Once VIN

drops below 21.5V, the regulator immediately resumes

normal operation. The regulator does not execute its

soft-start function when exiting an overvoltage condition.

Multiphase operation can be easily employed with the

synchronization and phase mode controls. Up to 6 phases

can be cascaded to run simultaneously with respect to

each other by programming the PHMODE pin to different

levels. The LTM4638 has MODE/CLKIN and CLKOUT pins

for PolyPhase operation of multiple devices or frequency

synchronization.

Pulling the RUN pin to GND forces the controller into its

shutdown state, turning off both power MOSFETs and

most of the internal control circuitry. At light load currents,

discontinuous mode (DCM) operation can be enabled to

achieve higher efficiency compared to continuous mode

(CCM) by pulling the MODE/CLKIN pin to GND. The

TRACK/SS pin is used for power supply tracking and

soft-start programming. See the Applications Informa-

tion section.

LTM4643 Datasheet(PDF) 10 Page - Analog Devices

LTM4643 Datasheet(HTML) 10 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Datasheet Descarga

Enlace URL