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LTM4604

4604f

OPERATION

Power Module Description

The LTM4604 is a standalone non-isolated switch mode

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

current with few external input and output capacitors.

This module provides a precise regulated output voltage

programmable via one external resistor from 0.8V DC to

5.0V DC over a 2.375V to 5.5V input voltage. A typical

application schematic is shown in Figure 15.

The LTM4604 has an integrated constant frequency cur-

rent mode regulator 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, the LTM4604 module has sufﬁcient

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 current

limit. In addition, foldback current limiting is provided

in an overcurrent condition while VOUT drops. Internal

overvoltage and undervoltage comparators pull the open-

drain PGOOD output low if the output feedback voltage exits

a ±7.5% 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.

Pulling the RUN pin below 0.5V forces the controller into its

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

current, the module works in continuous current mode by

default to achieve minimum output voltage ripple.

The TRACK pin is used for power supply tracking. See the

Applications Information section.

The LTM4604 is internally compensated to be stable over

a wide operating range. Table 4 provides a guideline for

input and output capacitance for several operating condi-

tions. An excel loop analysis tool is provided for transient

and stability analysis.

The FB pin is used to program the output voltage with a

single resistor connected to ground.

LTM4604 Datasheet(PDF) 8 Page - Linear Technology