Triple-Output Power Supply Controller for Notebook Computers

The MAX782 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, and dual PCMCIA VPP outputs powered by an integral flyback winding controller. Other functions include dual, low-dropout, micropower linear regulators for CMOS/RTC backup, and three 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. It 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 response 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. The integral flyback winding controller provides a low-cost, +15V high-side output that regulates even in the absence of a load on the main output.

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 MAX782 is a monolithic BiCMOS IC available in fine-pitch, SSOP surface-mount packages.

Applications

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

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

* Dual PCMCIA VPP Outputs (0V/5V/12V)

* Three Precision Comparators or Level Translators

* 95% Efficiency

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

* 5.5V to 30V Input Range

* Small SSOP Package

* Fixed Output Voltages Available:

* 3.3 (standard)

* 3.45 (High-Speed Pentium™)

* 3.6 (PowerPC™)