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LTM4614

4614fa

OPERATION

LTM4614 POWER MODULE DESCRIPTION

The LTM4614 is a standalone dual nonisolated switching

mode DC/DC power supply. It can deliver up to 4A of DC

output current for each channel with few external input

and output capacitors. This module provides two precisely

regulated output voltages programmable via one external

resistor for each channel from 0.8V DC to 5V DC over

a 2.375V to 5.5V input voltage. The typical application

schematic is shown in Figure 12.

The LTM4614 has two integrated constant frequency cur-

rent mode regulators, with built-in power MOSFETs with

fast switching speed. The typical switching frequency is

1.25MHz. With current mode control and internal feedback

loop compensation, these switching regulators have suf-

ﬁcient stability margins and good transient performance

under a wide range of operating conditions, and with a

wide range of output capacitors, even all ceramic output

capacitors.

Current mode control provides cycle-by-cycle fast cur-

rent limit. Besides, current limiting is provided in an

overcurrent condition with thermal shutdown. In addition,

internal overvoltage and undervoltage comparators pull the

open-drain PGOOD outputs low if the particular output

feedback voltage exits a ±7.5% window around the regu-

lation 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, or current limit is exceeded.

Pulling each speciﬁc RUN pin below 0.8V forces the spe-

ciﬁc regulator controller into its shutdown state, turning

off both M1 and M2 for each power stage. At low load

current, each regulator works in continuous current mode

by default to achieve minimum output voltage ripple.

The TRACK/SS pins are used for power supply tracking

and soft-start programming for each speciﬁc regulator.

See Applications Information section.

The LTM4614 is internally compensated to be stable over

the operating conditions. Table 4 provides a guideline for

input and output capacitance for several operating condi-

tions. The Linear Technology μModule Power Design Tool

will be provided for transient and stability analysis.

The FB pins are used to program the speciﬁc output volt-

age with a single resistor to ground.

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