The MAX786 is a system-engineered power-supply controller for notebook computers or similar batterypowered equipment. It provides two high-performance step-down (buck) pulse-width modulators (PWMs) for +3.3V and +5V. Other features include dual, low-dropout, micropower linear regulators for CMOS/RTC back-up, and two precision low-batterydetection comparators. High efficiency (95% at 2A; greater than 80% at loads from 5mA to 3A) is achieved through synchronous rectification and PWM operation at heavy loads, and Idle ModeTM operation at light loads. The MAX786 uses physically small components, thanks to high operating frequencies (300kHz/200kHz) and a new current-mode PWM architecture that allows for output filter capacitors as small as 30F per ampere of load. Line- and loadtransient responses are terrific, with a high 60kHz unitygain crossover frequency allowing output transients to be corrected within four or five clock cycles. Low system cost is achieved through a high level of integration and the use of low-cost, external N-channel MOSFETs.