AAT3216 Datasheet, PDF(9/16 Page) List of Unclassifed Manufacturers

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AAT3216 Datasheet, PDF (9/16 Pages) List of Unclassifed Manufacturers – 150mA MicroPower™ LDO with PowerOK

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AAT3216

150mA MicroPowerâ¢ LDO with PowerOK

Applications Information

To assure the maximum possible performance is

obtained from the AAT3216, please refer to the fol-

lowing application recommendations.

Input Capacitor

Typically a 1ÂµF or larger capacitor is recommend-

ed for CIN in most applications. A CIN capacitor is

not required for basic LDO regulator operation.

However, if the AAT3216 is physically located more

than 3 centimeters from an input power source, a

CIN capacitor will be needed for stable operation.

CIN should be located as close to the device VIN pin

as practically possible. CIN values greater than

1ÂµF 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 CIN. There is no specific

capacitor ESR requirement for CIN. However, for

150mA LDO regulator output operation, ceramic

capacitors are recommended for CIN 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 VOUT

and GND. The COUT capacitor connection to

the LDO regulator ground pin should be made as

direct as practically possible for maximum device

performance.

The AAT3216 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 1ÂµF to 10ÂµF.

Applications utilizing the exceptionally low output

noise and optimum power supply ripple rejection

characteristics of the AAT3216 should use 2.2ÂµF or

greater for COUT. If desired, COUT may be increased

without limit.

In low output current applications where output

load is less then 10mA, the minimum value for

COUT can be as low as 0.47ÂµF.

3216.2004.01.0.94

Capacitor Characteristics

Ceramic composition capacitors are highly recom-

mended over all other types of capacitors for use

with the AAT3216. Ceramic capacitors offer many

advantages over their tantalum and aluminum elec-

trolytic counterparts. A ceramic capacitor typically

has very low ESR, is lower cost, has a smaller PCB

footprint and is non-polarized. Line and load tran-

sient response of the LDO regulator is improved by

using low ESR ceramic capacitors. Since ceramic

capacitors are non-polarized, they are not prone to

incorrect connection damage.

Equivalent Series Resistance (ESR): ESR is a

very important characteristic to consider when

selecting a capacitor. ESR is the internal series

resistance associated with a capacitor, which

includes lead resistance, internal connections, size

and area, material composition and ambient tem-

perature. Typically capacitor ESR is measured in

milliohms for ceramic capacitors and can range to

more than several ohms for tantalum or aluminum

electrolytic capacitors.

Ceramic Capacitor Materials: Ceramic capaci-

tors less than 0.1ÂµF are typically made from NPO

or COG materials. NPO and COG materials are

typically tight tolerance very stable over tempera-

ture. Larger capacitor values are typically com-

posed of X7R, X5R, Z5U and Y5V dielectric mate-

rials. Large ceramic capacitors, typically greater

then 2.2ÂµF are often available in the low cost Y5V

and Z5U dielectrics. These two material types are

not recommended for use with LDO regulators

since the capacitor tolerance can vary more than

Â±50% over the operating temperature range of the

device. A 2.2ÂµF Y5V capacitor could be reduced to

1ÂµF over temperature, this could cause problems

for circuit operation. X7R and X5R dielectrics are

much more desirable. The temperature tolerance

of X7R dielectric is better than Â±15%.

Capacitor area is another contributor to ESR.

Capacitors which are physically large in size will have

a lower ESR when compared to a smaller sized

capacitor of an equivalent material and capacitance

value. These larger devices can improve circuit tran-

sient response when compared to an equal value

capacitor in a smaller package size.

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