1FEATURES

2• Two Synchronous Buck Regulators

• 180° Out of Phase Operation

• 200 kHz Fixed Nominal Frequency: LM5642

• 375 kHz Fixed Nominal Frequency: LM5642X

• Synchronizable Switching Frequency from 150

kHz to 250 kHz for the LM5642 and 200 kHz to

500 kHz for the LM5642X

• 4.5V to 36V Input Range

• 50 μA 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 4)

• 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 HTSSOP (Exposed PAD) Packages

APPLICATIONS

• Embedded Computer Systems

• Navigation Systems

• Telecom Systems

• Set-Top Boxes

• WebPAD

• Point Of Load Power Architectures

DESCRIPTION

The LM5642 series consists of two current mode

synchronous 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 150 kHz

and 250 kHz for the LM5642 and between 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 response 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

independent of the output load and output

capacitance making the soft-start behavior more

predictable and controllable than traditional 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.