LM5642XMT National Semiconductor, LM5642XMT Datasheet

LM5642XMT

Manufacturer Part Number

LM5642XMT

Description

IC,SMPS CONTROLLER,CURRENT-MODE,TSSOP,28PIN,PLASTIC

Manufacturer

National Semiconductor

Datasheets

1.LM5642MHX.pdf (28 pages)

2.LM5642XMT.pdf (28 pages)

Specifications of LM5642XMT

Rohs Compliant

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Download datasheet (805Kb)

LM5642/LM5642X

High Voltage, Dual Synchronous Buck Converter with

Oscillator Synchronization

General Description

The LM5642 series consists of two current mode syn-

chronous buck regulator controllers operating 180° out of

phase with each other at a normal switching frequency of

200kHz for the LM5642 and at 375kHz for the LM5642X.

Out of phase operation reduces the input RMS ripple current,

thereby significantly reducing the required input capacitance.

The switching frequency can be synchronized to an external

clock between 150kHz and 250kHz for the LM5642 and be-

tween 200 kHz and 500 kHz for the LM5642X. The two

switching regulator outputs can also be paralleled to operate

as a dual-phase, single output regulator.

The output of each channel can be independently adjusted

from 1.3V to 90% of Vin. An internal 5V rail is also available

externally for driving bootstrap circuitry.

Current-mode feedback control assures excellent line and

load regulation and wide loop bandwidth for excellent re-

sponse to fast load transients. Current is sensed across either

the Vds of the top FET or across an external current-sense

resistor connected in series with the drain of the top FET.

The LM5642 features analog soft-start circuitry that is inde-

pendent of the output load and output capacitance making the

soft-start behavior more predictable and controllable than tra-

ditional soft-start circuits.

Over-voltage protection is available for both outputs. A UV-

Delay pin is also available to allow delayed shut off time for

the IC during an output under-voltage event.

Typical Application Circuit

200601

Features

■

Applications

■

Two synchronous buck regulators

180° out of phase operation

200kHz fixed nominal frequency: LM5642

375kHz fixed nominal frequency: LM5642X

Synchronizable switching frequency from 150kHz to

250kHz for the LM5642 and 200kHz to 500kHz for the

LM5642X

4.5V to 36V input range

50µA Shutdown current

Adjustable output from 1.3V to 90% of Vin

0.04% (typical) line and load regulation accuracy

Current mode control with or without a sense resistor

Independent enable/soft-start pins allow simple sequential

startup configuration.

Configurable for single output parallel operation. (See

Figure 2)

Adjustable cycle-by-cycle current limit

Input under-voltage lockout

Output over-voltage latch protection

Output under-voltage protection with delay

Thermal shutdown

Self discharge of output capacitors when the regulator is

OFF

TSSOP and eTSSOP (Exposed PAD) packages

Embedded Computer Systems

Navigation Systems

Telecom Systems

Set-Top Boxes

WebPAD

Point Of Load Power Architectures

20060101

www.national.com

June 2007

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