LM2638 Datasheet | Texas Instruments

FEATURES - 2345 Provides 3 regulated voltages - Power Good flag and output enable - Charge pump pin - Switching Section - Synchronous rectification - 5-bit DAC programmable down to 1.3V - Typical ±1% DAC tolerance - Switching frequency: 50 k Hz to 1 MHz - Over-voltage protection - Two methods of over-current protection - Adaptive non-overlapping FET gate drives - Soft start without external capacitor - Linear Section - N-FET and NPN drive capability - Ultra fast response speed - Under voltage latch-off at 0.63V - Output voltages default to 1.5V and 2.5V yet adjustable APPLICATIONS - Embedded power supplies for motherboards - Triple DC/DC power supplies - Programmable high current DC/DC power supply DESCRIPTION The LM2638 provides a prehensive embedded power supply solution for motherboards hosting high performance MPUs such as Pentium™ II, M II™, K6™-2 and other similar high performance MPUs. The LM2638 incorporates a 5-bit programmable, synchronous buck switching controller and two high-speed linear regulator controllers in a 24-pin SO package. In a typical application, the switching controller supplies the MPU core, and the linear regulator controllers supply the GTL+ bus and the clock or graphics chip core. A charge pump pin helps provide the necessary voltage to power the linear sections when 12V is shut off during system standby such as STR mode. Switching Section - The switching regulator controller features an Intel-patible, 5-bit programmable output voltage, over-current and over-voltage protection, a power good signal, and a logic-controlled output enable. There are two user-selectable over-current protection methods. One provides accurate over-current protection with the use of an external sense resistor. The other saves cost by taking advantage of the r DS_ON of the highside FET. When there is an over voltage, the controller turns off the high side FET and turns on the low side. Linear Section - The two linear regulator controllers feature wide control...