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LTM4612

4612f

OPERATION

Power Module Description

The LTM4612 is a standalone nonisolated switching mode

DC/DC power supply. It can deliver 5A of DC output

current with some external input and output capacitors.

This module provides precisely regulated output voltage

programmable via one external resistor from 3.3VDC to

15VDC over a 5V to 36V wide input voltage. The typical

application schematic is shown in Figure 18.

The LTM4612 has an integrated constant on-time current

mode regulator, ultralow RDS(ON) FETs with fast switch-

ing speed and integrated Schottky diodes. The typical

switching frequency is 850kHz at full load. With current

mode control and internal feedback loop compensation,

the LTM4612 module has sufﬁcient stability margins and

good transient performance under a wide range of operat-

ing conditions and with a wide range of output capacitors,

even all ceramic output capacitors.

Current mode control provides cycle-by-cycle fast current

limiting. Moreover, foldback current limiting is provided

in an overcurrent condition while VFB drops. Internal

overvoltage and undervoltage comparators pull the open-

drain PGOOD output low if the output feedback voltage exits

a ±10% window around the regulation point. Furthermore,

in an overvoltage condition, internal top FET M1 is turned

off and bottom FET M2 is turned on and held on until the

overvoltage condition clears.

Input ﬁlter and noise cancellation circuitry reduce the

noise coupling to I/O sides, and ensure the electromag-

netic interference (EMI) meets the limits of CISPR 22 and

CISPR 25.

Pulling the RUN pin below 1V forces the controller into its

shutdown state, turning off both M1 and M2. At low load

currents, discontinuous mode (DCM) operation can be

enabled to achieve higher efﬁciency compared to continu-

ous mode (CCM) by setting FCB pin higher than 0.6V.

When the DRVCC pin is connected to INTVCC, an integrated

5V linear regulator powers the internal gate drivers. If a

5V external bias supply is applied on DRVCC pin, then an

efﬁciency improvement will occur due to the reduced power

loss in the internal linear regulator. This is especially true

at the higher input voltage range.

The MPGM, MARG0, and MARG1 pins are used to sup-

port voltage margining, where the percentage of margin

is programmed by the MPGM pin, and the MARG0 and

MARG1 selected margining. The PLLIN pin provides fre-

quency synchronization of the device to an external clock.

The TRACK/SS pin is used for power supply tracking and

soft-start programming.

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