The MAX783 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/+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 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 MAX783 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 that allows 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 MAX783 is similar to the MAX782, except the flyback winding is on the 3.3V inductor instead of the 5V inductor, the VPP outputs can be optionally programmed to 3.3V, and the device may be completely shut down.
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