AAT3220IGY-3.3-T1 查看數據表（PDF） - Skyworks Solutions

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AAT3220IGY-3.3-T1

150mA NanoPower LDO Linear Regulator

Skyworks Solutions 

DATA SHEET

AAT3220

150mA NanoPowerTM LDO Linear Regulator

Applications Information

To assure the maximum possible performance is obtained

from the AAT3220, please refer to the following applica-

tion recommendations.

Input Capacitor

Typically, a 1µF or larger capacitor is recommended for

CIN in most applications. A CIN capacitor is not required for

basic LDO regulator operation. However, if the AAT3220

is physically located any distance more than one or two

centimeters from the 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 1µF will offer superior input line tran-

sient response and will assist in maximizing the highest

possible power supply ripple rejection.

Ceramic, tantalum, or aluminum electrolytic capacitors

may be selected for CIN. There is no specific capacitor

ESR requirement for CIN. For 150mA LDO regulator out-

put operation, ceramic capacitors are recommended for

CIN due to their inherent capability over tantalum capac-

itors to withstand input current surges from low-imped-

ance sources such as batteries in portable devices.

Output Capacitor

For proper load voltage regulation and operational sta-

bility, a capacitor is required between pins VOUT and GND.

The COUT capacitor connection to the LDO regulator

ground pin should be as direct as practically possible for

maximum device performance. The AAT3220 has been

specifically designed to function with very low ESR

ceramic capacitors. Although the device is intended to

operate with low ESR capacitors, it is stable over a very

wide range of capacitor ESR, thus it will also work with

some higher ESR tantalum or aluminum electrolytic

capacitors. However, for best performance, ceramic

capacitors are recommended.

The value of COUT typically ranges from 0.47µF to 10µF;

however, 1µF is sufficient for most operating conditions.

If large output current steps are required by an applica-

tion, then an increased value for COUT should be consid-

ered. The amount of capacitance needed can be calcu-

lated from the step size of the change in the output load

current expected and the voltage excursion that the load

can tolerate.

The total output capacitance required can be calculated

using the following formula:

Where:

COUT =

∆I

∆V

∙ 15µF

DI = maximum step in output current

DV = maximum excursion in voltage that the load can

tolerate.

Note that use of this equation results in capacitor values

approximately two to four times the typical value needed

for an AAT3220 at room temperature. The increased

capacitor value is recommended if tight output tolerances

must be maintained over extreme operating conditions

and maximum operational temperature excursions. If

tantalum or aluminum electrolytic capacitors are used,

the capacitor value should be increased to compensate

for the substantial ESR inherent to these capacitor types.

Capacitor Characteristics

Ceramic composition capacitors are highly recommend-

ed over all other types of capacitors for use with the

AAT3220. Ceramic capacitors offer many advantages

over their tantalum and aluminum electrolytic counter-

parts. A ceramic capacitor typically has very low ESR, is

lower cost, has a smaller PCB footprint, and is non-

polarized. Line and load transient response of the LDO

regulator is improved by using low ESR ceramic capaci-

tors. Since ceramic capacitors are non-polarized, they

are less prone to damage if incorrectly connected.

Equivalent Series Resistance: ESR is a very impor-

tant characteristic to consider when selecting a capaci-

tor. ESR is the internal series resistance associated with

a capacitor that includes lead resistance, internal con-

nections, capacitor size and area, material composition,

and ambient temperature. Typically, capacitor ESR is

measured in milliohms for ceramic capacitors and can

range to more than several ohms for tantalum or alumi-

num electrolytic capacitors.

Ceramic Capacitor Materials: Ceramic capacitors less

than 0.1µF are typically made from NPO or C0G materi-

als. NPO and C0G materials generally have tight toler-

ance and are very stable over temperature. Larger

capacitor values are usually composed of X7R, X5R,

Z5U, or Y5V dielectric materials. Large ceramic capaci-

tors (i.e., greater than 2.2µF) are often available in low-

cost Y5V and Z5U dielectrics. These two material types

are not recommended for use with LDO regulators since

the capacitor tolerance can vary by more than ±50%

over the operating temperature range of the device. A

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202250A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 7, 2012

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