Part # LM2638 datasheet

Part Manufacturer: National Semiconductor

National Semiconductor

Part Description: LM2638 Motherboard Power Supply Solution with a 5-Bit Programmable Switching Controller and Two Linear Regulator Controllers

Part Details:

T LM2638 w May 1999 oLinear Motherboard LM2638 Regulator Motherboard Power Supply Solution with a 5-BitProgrammable Switching Controller and Two LinearRegulator Controllers General Description Both linear controllers have under voltage latch-off. Controllers Power The LM2638 provides a comprehensive embedded power Features supply solution for motherboards hosting high performanceMPUs such as PentiumTM II, M IITM, K6TM-2 and other similar n Provides 3 regulated voltages high performance MPUs. The LM2638 incorporates a 5-bit n Power Good flag and output enable Supply programmable, synchronous buck switching controller and n Charge pump pin two high-speed linear regulator controllers in a 24-pin SO Switching Section package. In a typical application, the switching controller n Synchronous rectification supplies the MPU core, and the linear regulator controllers n 5-bit DAC programmable down to 1.3V supply the GTL+ bus and the clock or graphics chip core. A n Typical ±1% DAC tolerance Solution charge pump pin helps provide the necessary voltage to n Switching frequency: 50 kHz to 1 MHz power the linear sections when 12V is shut off during systemstandby such as STR mode. n Over-voltage protection n Two methods of over-current protection Switching Section -- The switching regulator controller fea-tures an Intel-compatible, 5-bit programmable output volt- n Adaptive non-overlapping FET gate drives age, over-current and over-voltage protection, a power good n Soft start without external capacitor with signal, and a logic-controlled output enable. There are two Linear Section user-selectable over-current protection methods. One pro- n N-FET and NPN drive capability vides accurate over-current protection with the use of an ex- n Ultra fast response speed ternal sense resistor. The other saves cost by taking advan- n Under voltage latch-off at 0.63V a tage of the r of the high-side FET. When there is an DS_ON n Output voltages default to 1.5V and 2.5V yet adjustable 5-Bit

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LM2638.pdf Datasheet