1FEATURES
2• Two Synchronous Buck Regulators
• 180° Out of Phase Operation
• 4.5V to 30V Input Range
• Power Good Function Monitors Ch.1
• 37μA Shutdown Current
• 0.04% (typical) Line and Load Regulation Error
• 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 3).
• 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 package

APPLICATIONS
• Embedded Computer Systems
• High End Gaming Systems
• Set-top Boxes
• WebPAD

DESCRIPTION
The LM2642 consists of two current mode
synchronous buck regulator controllers with a
switching frequency of 300kHz.
The two switching regulator controllers operate 180°
out of phase. This feature reduces the input ripple
RMS current, thereby significantly reducing the
required input capacitance. 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 1.3 to VIN• maximum duty cycle. An internal 5V rail is also available externally for driving
bootstrap circuitry.
Current-mode feedback control assures excellent line
and load regulation and a 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. Current limit is
independently adjustable for each channel.
The LM2642 features analog soft-start circuitry that is
independent of the output load and output
capacitance. This makes the soft-start behavior more
predictable and controllable than traditional soft-start
circuits.
A PGOOD1 pin is provided to monitor the dc output
of channel 1. 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.