4.5V - 36V

SS/ON1

SS/ON2

SYNC

UV_Delay

Vout1

Vout2

LM5642/LM5642X

LM5642, LM5642X

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SNVS219K – JUNE 2003 – REVISED APRIL 2013

LM5642/LM5642X High Voltage, Dual Synchronous Buck Converter with Oscillator

Synchronization

Check for Samples: LM5642, LM5642X

1

FEATURES

DESCRIPTION

The LM5642 series consists of two current mode

2

•

Two Synchronous Buck Regulators

synchronous buck regulator controllers operating

•

180° Out of Phase Operation

180° out of phase with each other at a normal

•

200 kHz Fixed Nominal Frequency: LM5642

switching frequency of 200kHz for the LM5642 and at

375kHz for the LM5642X.

•

375 kHz Fixed Nominal Frequency: LM5642X

•

Synchronizable Switching Frequency from 150

Out of phase operation reduces the input RMS ripple

current, thereby significantly reducing the required

kHz to 250 kHz for the LM5642 and 200 kHz to

input capacitance. The switching frequency can be

500 kHz for the LM5642X

synchronized to an external clock between 150 kHz

•

4.5V to 36V Input Range

and 250 kHz for the LM5642 and between 200 kHz

•

50 µA Shutdown Current

and 500 kHz for the LM5642X. The two switching

regulator outputs can also be paralleled to operate as

•

Adjustable Output from 1.3V to 90% of Vin

a dual-phase, single output regulator.

•

0.04% (Typical) Line and Load Regulation

Accuracy

The output of each channel can be independently

adjusted from 1.3V to 90% of Vin. An internal 5V rail

•

Current Mode Control with or without a Sense

is also available externally for driving bootstrap

Resistor

circuitry.

•

Independent Enable/Soft-start Pins Allow

Current-mode feedback control assures excellent line

Simple Sequential Startup Configuration.

and load regulation and wide loop bandwidth for

•

Configurable for Single Output Parallel

excellent response to fast load transients. Current is

Operation. (See Figure 4)

sensed across either the Vds of the top FET or

•

Adjustable Cycle-by-cycle Current Limit

across an external current-sense resistor connected

in series with the drain of the top FET.

•

Input Under-voltage Lockout

•

Output Over-voltage Latch Protection

The LM5642 features analog soft-start circuitry that is

independent

of

the

output

load

and

output

•

Output Under-voltage Protection with Delay

capacitance making the soft-start behavior more

•

Thermal Shutdown

predictable and controllable than traditional soft-start

•

Self Discharge of Output Capacitors when the

circuits.

Regulator is OFF

Over-voltage protection is available for both outputs.

•

TSSOP and HTSSOP (Exposed PAD) Packages

A UV-Delay pin is also available to allow delayed shut

off time for the IC during an output under-voltage

APPLICATIONS

event.

•

Embedded Computer Systems

Typical Application Circuit

•

Navigation Systems

•

Telecom Systems

•

Set-Top Boxes

•

WebPAD

•

Point Of Load Power Architectures

1

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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2

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PRODUCTION DATA information is current as of publication date.

Copyright © 2003–2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.