1A, 97% Efficiency, 30µA Quiescent Current

Step-Up Converter with True Shutdown

8

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Detailed Description

The MAX8815A current-mode step-up DC-DC switching

converter uses a fixed-frequency PWM architecture with

True Shutdown. In normal mode, the converter switches

when needed, consuming only 30µA of quiescent cur-

rent. In forced-PWM mode (FPWM), the converter

switches every cycle at a constant frequency, thus

enabling noise filtering. The MAX8815A is highly effi-

cient, with an internal switch and synchronous rectifier.

Shutdown reduces the quiescent current to less than

0.1µA. Low quiescent current and high efficiency make

this device ideal for powering portable equipment.

The MAX8815A step-up DC-DC switching converter typ-

ically generates a 3.3V to 5V output voltage from a 1.2V

to 5.5V battery input voltage. The converter operates in

bootstrapped mode with the output powering the device

once the output voltage is ≥ 3V. The current limit is set at

2.5A to deliver 1A at 5V from a 2.5V input, or 500mA at

5V using a 2-cell 1.8V input. Internal soft-start limits the

inrush current to less than 500mA under no-load condi-

tions during startup.

The MAX8815A switches at a 2MHz frequency, allow-

ing for tiny external components. Internal compensation

further reduces the external component count in cost

and space-sensitive applications. The MAX8815A is

optimized for use in DSC and other applications requir-

ing low quiescent current for maximum battery life.

Figures 1a and 1b show the typical application circuits.

ON

SKIPB

POUT

BATT

LX

FB

OUTS

GND

ON

ON

3V

ON

ON

PGND

CONTROL

2MHz

OSCILLATOR

REFERENCE

EP

+

-

STARTUP

OSCILLATOR

MAX8815A

Functional Diagram