MAX799

19-0221; Rev 4; 9/05 KIT ATION EVALU E L B AVAILA Step-Down Controllers with Synchronous Rectifier for CPU Power ____________________________Features ♦ 96% Efficiency ♦ 4.5V to 30V Input Range ♦ 2.5V to 6V Adjustable Output ♦ Preset 3.3V and 5V Outputs (at up to 10A) ♦ Multiple Regulated Outputs ♦ +5V Linear-Regulator Output ♦ Precision 2.505V Reference Output ♦ Automatic Bootstrap Circuit ♦ 150kHz/300kHz Fixed-Frequency PWM Operation ♦ Programmable Soft-Start ♦ 375µA Typ Quiescent Current (V IN = 12V, V OUT = 5V) ♦ 1µA Typ Shutdown Current _______________General Description The MAX796/MAX797/MAX799 high-performance, stepdown DC-DC converters with single or dual outputs provide main CPU power in battery-powered systems. These buck controllers achieve 96% efficiency by using synchronous rectification and Maxim’s proprietary Idle Mode™ control scheme to extend battery life at full-load (up to 10A) and no-load outputs. Excellent dynamic response corrects output transients caused by the latest dynamic-clock CPUs within five 300kHz clock cycles. Unique bootstrap circuitry drives inexpensive N-channel MOSFETs, reducing system cost and eliminating the crowbar switching currents found in some PMOS/NMOS switch designs. The MAX796/MAX799 are specially equipped with a secondary feedback input (SECFB) for transformer-based dual-output applications. This secondary feedback path improves cross-regulation of positive (MAX796) or nega tive (MAX799) auxiliary outputs. The MAX797 has a logi...