Dual-Output Power Supply Controller for Notebook Computers

The MAX786 is a system-engineered power-supply controller for notebook computers or similar battery-powered 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-battery-detection 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 Mode™ 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 30µF per ampere of load. Line- and load-transient responses are terrific, with a high 60kHz unity-gain 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.

Other features include low-noise, fixed-frequency PWM operation at moderate to heavy loads, and a synchronizable oscillator for noise-sensitive applications such as electromagnetic pen-based systems and communicating computers. The MAX786 is a monolithic, BiCMOS IC available in fine-pitch, surface-mount SSOP packages.

Applications

* Communication Systems * Notebook Computers * Pen-Entry Systems * Portable Data Terminals

* Dual PWM Buck Controllers (+3.3V and +5V)

* Two Precision Comparators or Level Translators

* 95% Efficiency

* 420µA Quiescent Current, 70µA in Standby (linear regulators alive)

* 25µA Shutdown Current (+5V linear alive)

* 5.5V to 30V Input Range

* Small SSOP Package

* Fixed Output Voltages:

* 3.3V (standard)

* 3.45V (High-Speed Pentium®)

* 3.6V (PowerPC®)