AAT3258ITS-3.0-R-T1 datasheet(11/16 Pages) AAT

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LDO Regulator Applications

Input Capacitor

Typically, a 1µF or larger capacitor is recommend-

ed for C

IN in most applications.

A C

IN capacitor is

not required for basic LDO regulator operation.

However, if the AAT3258 is physically located more

than three centimeters from an input power source,

a C

IN capacitor will be needed for stable operation.

IN should be located as closely to the device VIN

pin as practically possible. C

IN values greater than

1µF will offer superior input line transient response

and will assist in maximizing the highest possible

power supply ripple rejection.

Ceramic, tantalum, or aluminum electrolytic capaci-

tors may be selected for C

IN. There is no specific

capacitor ESR requirement for C

IN.

However, for

300mA LDO regulator output operation, ceramic

capacitors are recommended for C

IN due to their

inherent capability over tantalum capacitors to with-

stand input current surges from low impedance

sources such as batteries in portable devices.

Output Capacitor

For proper load voltage regulation and operational

stability, a capacitor is required between pins V

OUT

and GND.

The C

OUT

capacitor connection to

the LDO regulator ground pin should be made as

direct as practically possible for maximum device

performance.

The AAT3258 has been specifically designed to func-

tion with very low ESR ceramic capacitors. For best

performance, ceramic capacitors are recommended.

Typical output capacitor values for maximum output

current conditions range from 1µF to 10µF.

Applications utilizing the exceptionally low output

noise and optimum power supply ripple rejection

characteristics of the AAT3258 should use 2.2µF or

greater for C

OUT. If desired, COUT may be increased

without limit.

In low output current applications where output

load is less than 10mA, the minimum value for

OUT can be as low as 0.47µF.

AAT3258

300mA LDO Linear Regulator with µP Reset

3258.2006.03.1.6

The microprocessor reset section monitors the supply

voltage to a microprocessor and asserts a reset sig-

nal whenever the V

DET voltage falls below a factory-

programmed threshold. This threshold is accurate

within +/-1.5% at 25°C. The reset signal remains

asserted for a minimum of 150ms after V

DET has risen

above the threshold, as shown in Figure 1.

To assure the maximum possible performance is

obtained from the AAT3258, please refer to the fol-

lowing application recommendations.

Figure 1: Reset Signal Assertion.

RESET

DET

RDY

AAT3258ITS-3.0-R-T1 Datasheet(PDF) 11 Page - Advanced Analog Technology, Inc.

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