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.