5-Output PMICs with DC-DC Core Supply for Low-Cost PDAs

The MAX8594/MAX8594A complete power-management chips for low-cost personal digital assistants (PDAs) operates from a 1-cell lithium-ion (Li+) or 3-cell NiMH battery. They include all regulators, outputs, and voltage monitors necessary for small portable devices while requiring a bare minimum of external components. Featured are three linear regulators, a boost DC-DC converter for LCD bias, an efficient 4MHz buck DC-DC converter for core power, a microprocessor (µP) reset output, and low-battery shutdown in a 0.8mm high thin QFN package.

The COR1 buck DC-DC converter supplies a pin-selectable output at 400mA. All linear regulators feature PMOS pass elements for efficient low-dropout operation. A MAIN LDO supplies 3.3V at 500mA. A securedigital (SD) card slot output supplies 3.3V at 500mA, and a COR2 LDO supplies 1.8V at 50mA. Each output has its own logic-controlled enable. For other output voltage combinations, contact Maxim.

An LCD bias boost DC-DC converter features an onboard MOSFET and True Shutdown™ when off. This means that during shutdown, input power is disconnected from the inductor so the boost output falls to 0V rather than remaining one diode drop below the input voltage. A µP reset output clears 20ms (typ) after the COR1 output achieves regulation to ensure an orderly start. In addition, the COR1 regulator is not started until the 3.3V main output is in regulation. Also included are a 1% accurate reference and low-battery monitor. Thermal shutdown protects the die from overheating.

The MAX8594/MAX8594A operate from a 3.1V to a 5.5V supply voltage and consume 46µA no-load supply current. They are packaged in a tiny, 4mm x 4mm, 24-pin thin QFN capable of dissipating 1.67W. The devices are specified for operation from -40°C to +85°C.

Applications

* Cell Phones/Cordless Phones * Handheld Devices * MP3 Players * Organizers * PDAs