LTM4612 Ver la hoja de datos (PDF) - Linear Technology
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LTM4612 Datasheet PDF : 24 Pages
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LTM4612
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.
4612f
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