MAX796

19-0221; Rev 3a; 11/97 UALS IT MAN TION K A ET U E L H A S A EV W DAT FOLLO Step-Down Controllers with Synchronous Rectifier for CPU Power ____________________________Features o 96% Efficiency o 4.5V to 30V Input Range o 2.5V to 6V Adjustable Output o o o o o o o o o 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 (VIN = 12V, VOUT = 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 negative (MAX799) auxiliary outputs...