The MAX1559 is a complete power-management chip for low-cost personal digital assistants (PDAs) and portable devices operating from a 1-cell lithium-ion (Li+) or 3-cell NiMH battery. It includes all the regulators, outputs, and voltage monitors necessary for small PDAs while requiring a bare minimum of external components. Featured are four linear regulators, a DC-DC boost converter for LCD bias, a microprocessor reset output, and low-battery shutdown in a miniature QFN package. For a compatible Li+ charger for both USB and AC adapter inputs, refer to the MAX1551*.
The four linear regulators feature PMOS pass elements for efficient low-dropout operation. A MAIN LDO supplies 3.3V at 500mA. A signal-detect (SD) card-slot output supplies 3.3V at 400mA. The COR1 LDO outputs 1V at 250mA, and the COR2 LDO supplies 1.8V at 30mA. The SD output and COR2 LDO have pin-controlled shutdown. For other output-voltage combinations, contact Maxim.
The DC-DC boost converter features an on-board MOSFET and True Shutdown™ when off. This means that during shutdown, input power is disconnected from the inductor so that the boost output falls to 0V rather than remaining one diode drop below the input voltage.
A µP reset output clears when the MAIN LDO achieves regulation to ensure an orderly start. Thermal shutdown protects the die from overheating.
The MAX1559 operates from a 3.1V to 5.5V supply and consumes 50mA of no-load supply current. It is packaged in a 1.3W, 16-pin thin QFN with a power pad on the underside of the package. The MAX1559 is specified for operation from -40°C to +85°C.
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