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LTM4648

4648f

For more information www.linear.com/LTM4648

operaTion

Power Module Description

The LTM4648 is a high performance single output stand-

alone nonisolated switching mode DC/DC power supply.

It can provide up to 10A output current with few exter-

nal input and output capacitors. This module provides

precisely regulated output voltage programmable via an

external resistor from 0.6VDC to 5VDC over a 2.375V to

5.5V input range. The typical application schematic is

shown in Figure 18.

The LTM4648 has an integrated constant-frequency cur-

rent mode regulator, power MOSFETs, inductor, and other

supporting discrete components. The typical switching

frequency is 450kHz. For switching noise-sensitive ap-

plications, it can be externally synchronized from 350kHz

to 650kHz. See the Applications Information section.

With current mode control and internal feedback loop

compensation, the LTM4648 module has sufficient stabil-

ity margins and good transient performance with a wide

range of output capacitors, especially with all ceramic

output capacitors.

Current mode control provides cycle-by-cycle fast current

limit in an overcurrent condition. An internal overvoltage

monitor protects the output voltage in the event of an

overvoltage >10%. The top MOSFET is turned off and the

bottom MOSFET is turned on until the output is cleared.

Pulling the RUN pin below 1.1V forces the regulator into a

shutdown state. The TRACK/SS pin is used for program-

ming the output voltage ramp and voltage tracking during

start-up. See the Application Information section.

The LTM4648 is internally compensated to be stable over

all operating conditions. Table 3 provides a guideline for

input and output capacitances for several operating con-

ditions. The Linear Technology µModule Power Design

Tool will be provided for transient and stability analysis.

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

single external resistor to ground.

A remote sense amplifier is provided in the LTM4648 for

accuratelysensingoutputvoltages≤3.3Vattheloadpoint.

Multiphase operation can be easily employed with the

synchronization inputs using an external clock source.

See application examples.

High efficiency at light loads can be accomplished with

selectableBurstModeoperationusingtheMODEpin.These

light load features will accommodate battery operation.

Efficiency graphs are provided for light load operation in

the Typical Performance Characteristics section.

A diode connected PNP transistor with base and collector

grounded is included in the module as a general purpose

single-ended temperature monitor. The temperature

monitor is intended to be used as a general temperature

monitor, see Applications Information section

The switching node pins are available for functional opera-

tion monitoring and a resistor-capacitor snubber circuit

can be careful placed on the switching node pin to ground

to dampen any high frequency ringing on the transition

edges.SeetheApplicationsInformationsectionfordetails.

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