LM5642

LM5642 High Voltage, Dual Synchronous Buck Converter with Oscillator Synchronization September 2003 LM5642 High Voltage, Dual Synchronous Buck Converter with Oscillator Synchronization General Description The LM5642 consists of two current mode synchronous buck regulator controllers operating 180˚ out of phase with each other at a normal switching frequency of 200kHz. Out of phase operation reduces the input ripple RMS current, thereby significantly reducing the required input capacitance. The switching frequency can be synchronized to an external clock between 150kHz and 250kHz. 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 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 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 currentsense 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 UVDelay pin is also available to allow delayed shut off time for the I...