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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.
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