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LM5642 Datasheet(PDF) 1 Page - National Semiconductor (TI) |
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LM5642 Datasheet(HTML) 1 Page - National Semiconductor (TI) |
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1 / 24 page  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 cur- rent, thereby significantly reducing the required input capaci- tance. The switching frequency can be synchronized to an external clock between 150kHz and 250kHz. The two switch- ing 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 current- sense resistor connected in series with the drain of the top FET. The LM5642 features analog soft-start circuitry that is inde- pendent 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. Features n Two synchronous buck regulators n 180˚ out of phase operation n Synchronizable switching frequency from 150kHz to 250kHz n 4.5V to 36V input range n 50µA Shutdown current n Adjustable output from 1.3V to 90% of Vin n 0.04% (typical) line and load regulation error n Current mode control with or without a sense resistor n Independent enable/soft-start pins allow simple sequential startup configuration. n Configurable for single output parallel operation. (See Figure 2) n Adjustable cycle-by-cycle current limit n Input under-voltage lockout n Output over-voltage latch protection n Output under-voltage protection with delay n Thermal shutdown n Self discharge of output capacitors when the regulator is OFF n TSSOP package Applications n Embedded Computer Systems n Telecom Systems n Set-Top Boxes n WebPAD n Point Of Load Power Architectures Typical Application Circuit 20060101 September 2003 © 2003 National Semiconductor Corporation DS200601 www.national.com |
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