AAT3221IGV-2.7-T1 - AnalogicTech

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

Preliminary Information

3221.2002.03.0.941

PowerLinear™

General Description

The AAT3221 and AAT3222 PowerLinear™

NanoPower Low Dropout Linear Regulators are

ideal for portable applications where extended bat-

tery life is critical. This device features extremely

low quiescent current which is typically 1.1µA.

Dropout voltage is also very low, typically less than

200mV at the maximum output current of 150mA.

The AAT3221/2 has an Enable pin feature, which

when asserted will enter the LDO regulator into a

shutdown mode removing power from its load and

offering extended power conservation capabilities

for portable battery powered applications.

The AAT3221/2 has output short circuit and over

current protection. In addition, the device also has

an over temperature protection circuit, which will

shutdown the LDO regulator during extended over-

current events. It is available with active high or

active low enable input.

The AAT3221 and AAT3222 are available in space

saving 5-pin SOT23 packages. The AAT3221 is

also available in the 8-pin SC70JW package. The

device is rated over a -40°C to 85°C temperature

range. Since only a small, 1µF ceramic output

capacitor is recommended, often the only space

used is that occupied by the AAT3221/2 itself. The

AAT3221/2 is truly a compact and cost effective volt-

age conversion solution.

The AAT3221/2 is similar to the AAT3220 with the

exception that it offers further power savings with

its enable pin.

Features

• 1.1 µA Quiescent Current

• Low Dropout: 200 mV (typical)

• Guaranteed 150 mA Output

• High accuracy: ±2%

• Current limit protection

• Over-Temperature protection

• Extremely Low power shutdown mode

• Low Temperature Coefficient

• Factory programmed output voltages

• 1.8V to 3.5V

• Stable operation with virtually any output

capacitor type

• Active high or low Enable pin

• 5-pin SOT23 or 8-pin SC70JW packages

• 4kV ESD

Applications

• Cellular Phones

• Notebook Computers

• Portable Communication Devices

• Handheld Electronics

• Remote Controls

• Digital Cameras

• PDAs

Typical Application

AAT3221/2

INPUT

GND

OUT

OUTPUT

GNDGND

ENABLE

(ENABLE)

CIN

1µF

COUT

1µF

(EN)

Pin Descriptions

Pin Configuration

AAT3221 AAT3221 AAT3222

SOT23-5 SC70JW-8 SOT23-5

(Top View) (Top View) (Top View)

3NC

OUT

EN (EN)

GND

(EN) EN

1 2

GND

OUT

3NC

OUT

(EN) EN 4

GND

Pin #

AAT3221 AAT3222

SOT23-5 SC70JW-8 Symbol Function

1 2 2 IN Input pin

2 5, 6, 7, 8 1 GND Ground connection pin

3 4 5 EN (EN) Enable Input. Logic compatible enable with

active high or active low option available; see

Ordering Information and Applications

Information for details.

4 3 4 NC Not Connected

5 1 3 OUT Output pin - should be decoupled with 1µF or

greater capacitor

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

23221.2002.03.0.94

Absolute Maximum Ratings (TA=25°C unless otherwise noted)

Note: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at con-

ditions other than the operating conditions specified is not implied. Only one Absolute Maximum rating should be applied at any one time.

Thermal Information

Note 1: Mounted on a demo board.

Recommended Operating Conditions

Symbol Description Rating Units

VIN Input Voltage (VOUT+0.34) to 5.5 V

T Ambient Temperature Range -40 to +85 °C

Symbol Description Rating Units

ΘJA Thermal Resistance (SOT23-5 or SC70JW-8)1150 °C/W

PDPower Dissipation (SOT23-5 or SC70JW-8)1667 mW

Symbol Description Value Units

VIN Input Voltage -0.3 to 6 V

VEN EN (EN) to GND Voltage -0.3 to 6 V

VENIN(MAX) Maximum EN (EN) to Input Voltage 0.3 V

IOUT Maximum DC Output Current PD/(VIN-VO)mA

TJOperating Junction Temperature Range -40 to 150 °C

TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

3221.2002.03.0.943

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

43221.2002.03.0.94

Electrical Characteristics (VIN=VOUT(NOM)+1V, IOUT=1mA, COUT=1µF, TA=25°C unless otherwise noted)

Note 1: VDO is defined as VIN - VOUT when VOUT is 98% of nominal.

Symbol Description Conditions Min Typ Max Units

VOUT DC Output Voltage Tolerance -2.0 2.0 %

VOUT=2.8V -1.4 1.4

IOUT Output Current VOUT > 1.2 V 150 mA

ISC Short Circuit Current VOUT < 0.4 V 350 mA

IQGround Current VIN = 5 V, no load 1.1 2.5 µA

ISD Shutdown Current EN = inactive 20 nA

∆VOUT/VOUT Line Regulation VIN = 4.0-5.5 V 0.15 0.4 %/V

VOUT = 1.8 1.0 1.65

VOUT = 2.0 0.9 1.58

VOUT = 2.3 0.8 1.45

VOUT = 2.4 0.8 1.40

VOUT = 2.5 0.8 1.35

∆VOUT/VOUT Load Regulation IL=1 to 100mA VOUT = 2.7 0.7 1.25 %

VOUT = 2.8 0.7 1.20

VOUT = 2.85 0.7 1.20

VOUT = 3.0 0.6 1.15

VOUT = 3.3 0.5 1.00

VOUT = 3.5 0.5 1.00

VOUT = 1.8 290 340

VOUT = 2.0 265 315

VOUT = 2.3 230 275

VOUT = 2.4 220 265

VOUT = 2.5 210 255

VDO Dropout Voltage1IOUT = 100mA VOUT = 2.7 200 240 mV

VOUT = 2.8 190 235

VOUT = 2.85 190 230

VOUT = 3.0 190 225

VOUT = 3.3 180 220

VOUT = 3.5 180 220

VEN(L) EN Input Low Voltage 0.8 V

VEN(H) EN Input High Voltage VIN = 2.7 V to 3.6 V 2.0 V

VIN = 5 V 2.4 V

IEN(SINK) EN Input leakage VON = 5.5 V 0.01 1 µA

PSRR Power Supply Rejection Ratio 100 Hz 50 dB

TSD Over Temp Shutdown Threshold 140 °C

THYS Over Temp Shutdown Hysteresis 20 °C

eNOutput Noise 350 µVRMS

TCOutput Voltage Temp. Coefficient 80 PPM/°C

AAT3221/2

150mA NanoPower LDO Linear Regulator

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Typical Characteristics

(Unless otherwise noted, VIN = VOUT + 1V, TA= 25 C, COUT = 5.6 F ceramic, IOUT = 100mA)

PSRR with 10mA Load

1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Frequency (Hz)

PSRR (dB)

Supply Current vs. Input Voltage

0123 456

Input ( V )

Input (µA) with No Load

80°C

-30°C

25°C

Drop-out Voltage vs. Output Current

100

200

300

40 0

0255075100125150

Output (mA)

Drop-out (mV )

80°C

-30°C

25°C

Output Voltage vs. Input Voltage

2.99

3.01

3.02

3.03

3.5 4 4.5 5 5.5

Input ( V )

Output (V)

1mA

10mA

40mA

Output Voltage v. Input Voltage

2.5

2.6

2.7

2.8

2.9

3.1

2.7 2.9 3.1 3.3 3.5

Input (V)

Output (V)

1mA

10mA

40mA

Output Voltage vs. Output Current

2.97

2.98

2.99

3.01

3.02

3.03

020406080100

Output (mA)

Output (V)

80°C

25°C

-30°C

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

63221.2002.03.0.94

(Unless otherwise noted, VIN = VOUT + 1V, TA= 25°C, COUT = 5.6µF ceramic, IOUT = 100mA)

Load Transient - 1 mA / 80 mA

-10 1 2 3

Time (ms)

Output (V)

160

240

320

Output (mA)

Output

Load Transient - 1 mA / 40 mA

-10 123

Time (ms)

Output (V)

160

240

320

Output (m A)

Output

Line Response with 100mA Load

2.6

2.8

3.2

3.4

3.6

3.8

-200 0 200 400 600 800

Time (µs)

Output Voltage (V )

Input Voltage ( V )

Input

Output

Line Response with 10mA Load

2.6

2.8

3.2

3.4

3.6

3.8

-200 0 200 400 600 800

Time (µs)

Output Voltage ( V )

Input Voltage ( V )

Input

Output

Line Response with 1mA Load

2.6

2.8

3.2

3.4

3.6

3.8

-200 0 200 400 600 800

Time (µs)

Output Voltage ( V )

Input Voltage ( V )

Input

Output

Noise Spectrum

-30

-20

-10

1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

Frequency (Hz)

Noise (dB µV/rt Hz)

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

3221.2002.03.0.947

(Unless otherwise noted, VIN = VOUT + 1V, TA= 25°C, COUT = 5.6µF ceramic, IOUT = 100mA)

Turn On with 100mA Load

-10 12

Time (ms)

Output (V)

-1

Enable ( V )

Output

Enable

Power Up with 100mA Load

-10 12

Time (ms)

Output (V)

-3

-2

-1

Input ( V )

Output

Enable

Turn On with 10mA Load

-10 12

Time (ms)

Output (V)

-1

Enable ( V )

Output

Enable

Power Up with 10mA Load

-10 12

Time (ms)

Output (V)

-3

-2

-1

Input (V)

Output

Enable

Turn On with 1mA Load

-10 12

Time (ms)

Output (V)

-1

Enable ( V )

Output

Enable

Power Up with 1mA Load

-10 12

Time (ms)

Output (V)

-3

-2

-1

Input (V)

Output

Enable

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

83221.2002.03.0.94

Functional Block Diagram

Over-Current

Protection

Over-Temp

Protection

VREF

OUT

GND

Functional Description

The AAT3221 and AAT3222 are intended for LDO

regulator applications where output current load

requirements range from No Load to 150mA. The

advanced circuit design of the AAT3221/2 has been

optimized for very low quiescent or ground current

consumption making it ideal for use in power man-

agement systems for small battery operated

devices. The typical quiescent current level is just

1.1µA. The AAT3221/2 also contains an enable cir-

cuit, which has been provided to shutdown the LDO

regulator for additional power conservation in

portable products. In the shutdown state the LDO

draws less than 1µA from input supply.

The LDO also demonstrates excellent power sup-

ply ripple rejection (PSRR), and load and line tran-

sient response characteristics. The AAT3221/2 is a

truly high performance LDO regulator especially

well suited for circuit applications which are sensi-

tive to load circuit power consumption and extend-

ed battery life.

The LDO regulator output has been specifically

optimized to function with low cost, low ESR

ceramic capacitors. However, the design will allow

for operation with a wide range of capacitor types.

The AAT3221/2 has complete short circuit and

thermal protection. The integral combination of

these two internal protection circuits give the

AAT3221/2 a comprehensive safety system to

guard against extreme adverse operating condi-

tions. Device power dissipation is limited to the

package type and thermal dissipation properties.

Refer to the thermal considerations section for

details on device operation at maximum output

load levels.

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

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Applications Information

To assure the maximum possible performance is

obtained from the AAT3221/2, please refer to the

following application 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 AAT3221/2 is physically located any

distance more than a centimeter or two 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 val-

ues greater than 1µF will offer superior input line

transient response and will assist in maximizing the

power supply ripple rejection.

Ceramic, tantalum or aluminum electrolytic capaci-

tors may be selected for CIN as there is no specific

capacitor ESR requirement. For 150mA LDO reg-

ulator output operation, ceramic capacitors are rec-

ommended for CIN due to their inherent capability

over tantalum capacitors to withstand input current

surges from low impedance sources such as bat-

teries 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 per-

formance. The AAT3221/2 has been specifically

designed to function with very low ESR ceramic

capacitors. Although the device is intended to oper-

ate with these 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 perform-

ance, 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

application, then an increased value for COUT

should be considered. The amount of capacitance

needed can be calculated from the step size of the

change in output load current expected and the

voltage excursion that the load can tolerate.

The total output capacitance required can be cal-

culated using the following formula:

COUT = ∆I × 15µF

∆V

Where:

∆I = maximum step in output current

∆V = 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 AAT3221/2 at room tempera-

ture. The increased capacitor value is recommend-

ed if tight output tolerances must be maintained over

extreme operating conditions and maximum opera-

tional temperature excursions. If tantalum or alu-

minum 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 recom-

mended over all other types of capacitors for use

with the AAT3221/2. Ceramic capacitors offer

many advantages over their tantalum and alu-

minum electrolytic counterparts. A ceramic capac-

itor 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 capacitors.

Since ceramic capacitors are non-polarized, they

are less prone to damage if connected incorrectly.

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,

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 aluminum electrolytic capacitors.

Ceramic Capacitor Materials: Ceramic capacitors

less than 0.1µF are typically made from NPO or

COG materials. NPO and COG materials are typi-

cally tight tolerance and very stable over tempera-

ture. Larger capacitor values are typically composed

of X7R, X5R, Z5U and Y5V dielectric materials.

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

10 3221.2002.03.0.94

Large ceramic capacitors, typically greater than

2.2µF are often available in the low cost Y5V and Z5U

dielectrics. These two material types are not recom-

mended for use with LDO regulators since the capac-

itor tolerance can vary more than ±50% over the

operating temperature range of the device. A 2.2µF

Y5V capacitor could be reduced to 1µF over the full

operating temperature range. This can cause prob-

lems for circuit operation and stability. X7R and X5R

dielectrics are much more desirable. The tempera-

ture tolerance of X7R dielectric is better than ±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 equivalent material and capaci-

tance value. These larger devices can also improve

circuit transient response when compared to an

equal value capacitor in a smaller package size.

Consult capacitor vendor data sheets carefully when

selecting capacitors for use with LDO regulators.

Enable Function

The AAT3221/2 features an LDO regulator enable /

disable function. This pin (EN) is compatible with

CMOS logic. Active high or active low options are

available (see Ordering Information). For a logic high

signal, the EN control level must be greater then 2.4

volts. A logic low signal is asserted when the voltage

on the EN pin falls below 0.6 volts. For example, the

active high version 3221/2 will turn on when a logic

high is applied to the EN pin. If the enable function is

not needed in a specific application, it may be tied to

the respective voltage level to keep the LDO regula-

tor in a continuously on state; e.g. the active high ver-

sion 3221/2 will tie VIN to EN to remain on.

Short Circuit Protection and Thermal

Protection

The AAT3221/2 is protected by both current limit

and over temperature protection circuitry. The

internal short circuit current limit is designed to acti-

vate when the output load demand exceeds the

maximum rated output. If a short circuit condition

were to continually draw more than the current limit

threshold, the LDO regulator's output voltage will

drop to a level necessary to supply the current

demanded by the load. Under short circuit or other

over current operating conditions, the output volt-

age will drop and the AAT3221/2's die temperature

will increase rapidly. Once the regulator's power

dissipation capacity has been exceeded and the

internal die temperature reaches approximately

140°C the system thermal protection circuit will

become active. The internal thermal protection cir-

cuit will actively turn off the LDO regulator output

pass device to prevent the possibility of over tem-

perature damage. The LDO regulator output will

remain in a shutdown state until the internal die

temperature falls back below the 140°C trip point.

The interaction between the short circuit and ther-

mal protection systems allow the LDO regulator to

withstand indefinite short circuit conditions without

sustaining permanent damage.

No-Load Stability

The AAT3221/2 is designed to maintain output volt-

age regulation and stability under operational no-

load conditions. This is an important characteristic

for applications where the output current may drop

to zero. An output capacitor is required for stability

under no load operating conditions. Refer to the

output capacitor considerations section for recom-

mended typical output capacitor values.

Thermal Considerations and High

Output Current Applications

The AAT3221/2 is designed to deliver a continuous

output load current of 150mA under normal operat-

ing conditions. The limiting characteristic for the

maximum output load safe operating area is essen-

tially package power dissipation and the internal pre-

set thermal limit of the device. In order to obtain high

operating currents, careful device layout and circuit

operating conditions need to be taken into account.

The following discussions will assume the LDO reg-

ulator is mounted on a printed circuit board utilizing

the minimum recommended footprint and the print-

ed circuit board is 0.062inch thick FR4 material with

one ounce copper.

At any given ambient temperature (TA) the maxi-

mum package power dissipation can be deter-

mined by the following equation:

PD(MAX) = [TJ(MAX) - TA] / ΘJA

Constants for the AAT3221/2 are TJ(MAX), the maxi-

mum junction temperature for the device which is

125°C and ΘJA = 150°C/W, the package thermal

resistance. Typically, maximum conditions are cal-

culated at the maximum operating temperature

where TA= 85°C, under normal ambient conditions

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

3221.2002.03.0.9411

TA= 25°C. Given TA= 85°, the maximum package

power dissipation is 267mW. At TA= 25°C°, the

maximum package power dissipation is 667mW.

The maximum continuous output current for the

AAT3221/2 is a function of the package power dis-

sipation and the input to output voltage drop across

the LDO regulator. Refer to the following simple

equation:

IOUT(MAX) < PD(MAX) / (VIN - VOUT)

For example, if VIN = 5V, VOUT = 2.5V and TA= 25°,

IOUT(MAX) < 267mA. The output short circuit protec-

tion threshold is set between 150mA and 300mA. If

the output load current were to exceed 267mA or if

the ambient temperature were to increase, the inter-

nal die temperature will increase. If the condition

remained constant and the short circuit protection

did not activate, there would be a potential damage

hazard to LDO regulator since the thermal protection

circuit will only activate after a short circuit event

occurs on the LDO regulator output.

To figure what the maximum input voltage would be

for a given load current refer to the following equa-

tion. This calculation accounts for the total power

dissipation of the LDO Regulator, including that

caused by ground current.

PD(MAX) = (VIN - VOUT)IOUT + (VIN x IGND)

This formula can be solved for VIN to determine

the maximum input voltage.

VIN(MAX) = (PD(MAX) + (VOUT x IOUT)) / (IOUT + IGND)

The following is an example for an AAT3221/2 set

for a 2.5 volt output:

From the discussion above, PD(MAX) was deter-

mined to equal 667mW at TA= 25°C.

VOUT = 2.5 volts

IOUT = 150mA

IGND = 1.1µA

VIN(MAX)=(667mW+(2.5Vx150mA))/(150mA +1.1µA)

VIN(MAX) = 6.95V

Thus, the AAT3221/2 can sustain a constant 2.5V

output at a 150mA load current as long as VIN is ≤

6.95V at an ambient temperature of 25°C. 5.5V is

the maximum input operating voltage for the

AAT3221/2, thus at 25°C, the device would not have

any thermal concerns or operational VIN(MAX) limits.

This situation can be different at 85°C. The follow-

ing is an example for an AAT3221/2 set for a 2.5

volt output at 85°C:

From the discussion above, PD(MAX) was deter-

mined to equal 267mW at TA= 85°C.

VOUT = 2.5 volts

IOUT = 150mA

IGND = 1.1µA

VIN(MAX)=(267mW+(2.5Vx150mA))/(150mA +1.1µA)

VIN(MAX) = 4.28V

Higher input to output voltage differentials can be

obtained with the AAT3221/2, while maintaining

device functions in the thermal safe operating area.

To accomplish this, the device thermal resistance

must be reduced by increasing the heat sink area

or by operating the LDO regulator in a duty cycled

mode.

For example, an application requires VIN = 5.0V

while VOUT = 2.5V at a 150mA load and TA= 85°C.

VIN is greater than 4.28V, which is the maximum

safe continuous input level for VOUT = 2.5V at

150mA for TA= 85°C. To maintain this high input

voltage and output current level, the LDO regulator

must be operated in a duty cycled mode. Refer to

the following calculation for duty cycle operation:

PD(MAX) is assumed to be 267mW

IGND = 1.1µA

IOUT = 150mA

VIN = 5.0 volts

VOUT = 2.5 volts

%DC = 100(PD(MAX) / ((VIN - VOUT)IOUT + (VIN x IGND))

%DC=100(267mW/((5.0V-2.5V)150mA+(5.0Vx1.1µA))

%DC = 71.2%

For a 150mA output current and a 2.5 volt drop

across the AAT3221/2 at an ambient temperature

of 85°C, the maximum on time duty cycle for the

device would be 71.2%.

The following family of curves shows the safe oper-

ating area for duty cycled operation from ambient

room temperature to the maximum operating level.

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

12 3221.2002.03.0.94

High Peak Output Current Applications

Some applications require the LDO regulator to

operate at continuous nominal levels with short

duration high current peaks. The duty cycles for

both output current levels must be taken into

account. To do so, one would first need to calcu-

late the power dissipation at the nominal continu-

ous level, then factor in the addition power dissipa-

tion due to the short duration high current peaks.

For example, a 2.5V system using a AAT3221/

2IGV-2.5-T1 operates at a continuous 100mA load

current level and has short 150mA current peaks.

The current peak occurs for 378µs out of a 4.61ms

period. It will be assumed the input voltage is 5.0V.

First, the current duty cycle percentage must be

calculated:

% Peak Duty Cycle: X/100 = 378ms/4.61ms

% Peak Duty Cycle = 8.2%

The LDO Regulator will be under the 100mA load

for 91.8% of the 4.61ms period and have 150mA

peaks occurring for 8.2% of the time. Next, the

continuous nominal power dissipation for the

100mA load should be determined then multiplied

by the duty cycle to conclude the actual power dis-

sipation over time.

PD(MAX) = (VIN - VOUT)IOUT + (VIN x IGND)

PD(100mA) = (5.0V - 2.5V)100mA + (5.0V x 1.1mA)

PD(100mA) = 250mW

PD(91.8%D/C) = %DC x PD(100mA)

PD(91.8%D/C) = 0.918 x 250mW

PD(91.8%D/C) = 229.5mW

Device Duty Cycle vs. VDROP

VOUT = 2.5V @ 85 degrees C

0.5

1.5

2.5

3.5

0 10 2030 405060 7080 90100

Duty Cycle (%)

Voltage Drop (V)

200mA

150mA

100mA

Device Duty Cycle vs. VDROP

VOUT = 2.5V @ 50 degrees C

0.5

1.5

2.5

3.5

0 102030405060708090100

Duty Cycle (%)

Voltage Drop (V)

200mA

150mA

Device Duty Cycle vs. VDROP

VOUT = 2.5V @ 25 degrees C

0.5

1.5

2.5

3.5

0 102030405060708090100

Duty Cycle (%)

Voltage Drop (V)

200mA

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

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The power dissipation for a 100mA load occurring

for 91.8% of the duty cycle will be 229.5mW. Now

the power dissipation for the remaining 8.2% of the

duty cycle at the 150mA load can be calculated:

PD(MAX) = (VIN - VOUT)IOUT + (VIN x IGND)

PD(150mA) = (5.0V - 2.5V)150mA + (5.0V x 1.1mA)

PD(150mA) = 375mW

PD(8.2%D/C) = %DC x PD(150mA)

PD(8.2%D/C) = 0.082 x 375mW

PD(8.2%D/C) = 30.75mW

The power dissipation for a 150mA load occurring

for 8.2% of the duty cycle will be 20.9mW. Finally,

the two power dissipation levels can summed to

determine the total true power dissipation under the

varied load.

PD(total) = PD(100mA) + PD(150mA)

PD(total) = 229.5mW + 30.75mW

PD(total) = 260.25mW

The maximum power dissipation for the AAT3221/2

operating at an ambient temperature of 85°C is

267mW. The device in this example will have a total

power dissipation of 260.25mW. This is within the

thermal limits for safe operation of the device.

Printed Circuit Board Layout

Recommendations

In order to obtain the maximum performance from

the AAT3221/2 LDO regulator, very careful attention

must be considered in regard to the printed circuit

board layout. If grounding connections are not prop-

erly made, power supply ripple rejection and LDO

regulator transient response can be compromised.

The LDO Regulator external capacitors CIN and

COUT should be connected as directly as possible

to the ground pin of the LDO Regulator. For maxi-

mum performance with the AAT3221/2, the ground

pin connection should then be made directly back

to the ground or common of the source power sup-

ply. If a direct ground return path is not possible

due to printed circuit board layout limitations, the

LDO ground pin should then be connected to the

common ground plane in the application layout.

Ordering Information

Output Voltage Enable Package Marking Part Number

Bulk Tape and Reel

1.8V Active high SOT23-5 N/A AAT3221IGV-1.8-T1

2.0V Active high SOT23-5 N/A AAT3221IGV-2.0-T1

2.3V Active high SOT23-5 N/A AAT3221IGV-2.3-T1

2.4V Active high SOT23-5 N/A AAT3221IGV-2.4-T1

2.5V Active high SOT23-5 N/A AAT3221IGV-2.5-T1

2.7V Active high SOT23-5 N/A AAT3221IGV-2.7-T1

2.8V Active high SOT23-5 N/A AAT3221IGV-2.8-T1

2.85V Active high SOT23-5 N/A AAT3221IGV-2.85-T1

3.0V Active high SOT23-5 N/A AAT3221IGV-3.0-T1

3.3V Active high SOT23-5 N/A AAT3221IGV-3.3-T1

3.5V Active high SOT23-5 N/A AAT3221IGV-3.5-T1

1.8V Active high SC70JW-8 N/A AAT3221IJS-1.8-T1

2.0V Active high SC70JW-8 N/A AAT3221IJS-2.0-T1

2.3V Active high SC70JW-8 N/A AAT3221IJS-2.3-T1

2.4V Active high SC70JW-8 N/A AAT3221IJS-2.4-T1

2.5V Active high SC70JW-8 N/A AAT3221IJS-2.5-T1

2.7V Active high SC70JW-8 N/A AAT3221IJS-2.7-T1

2.8V Active high SC70JW-8 N/A AAT3221IJS-2.8-T1

2.85V Active high SC70JW-8 N/A AAT3221IJS-2.85-T1

3.0V Active high SC70JW-8 N/A AAT3221IJS-3.0-T1

3.3V Active high SC70JW-8 N/A AAT3221IJS-3.3-T1

3.5V Active high SC70JW-8 N/A AAT3221IJS-3.5-T1

1.8V Active high SOT23-5 N/A AAT3222IGV-1.8-T1

2.0V Active high SOT23-5 N/A AAT3222IGV-2.0-T1

2.3V Active high SOT23-5 N/A AAT3222IGV-2.3-T1

2.4V Active high SOT23-5 N/A AAT3222IGV-2.4-T1

2.5V Active high SOT23-5 N/A AAT3222IGV-2.5-T1

2.7V Active high SOT23-5 N/A AAT3222IGV-2.7-T1

2.8V Active high SOT23-5 N/A AAT3222IGV-2.8-T1

2.85V Active high SOT23-5 N/A AAT3222IGV-2.85-T1

3.0V Active high SOT23-5 N/A AAT3222IGV-3.0-T1

3.3V Active high SOT23-5 N/A AAT3222IGV-3.3-T1

3.5V Active high SOT23-5 N/A AAT3222IGV-3.5-T1

2.8V Active low SOT23-5 N/A AAT3221IGV-2.8-2 T1

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

14 3221.2002.03.0.94

AAT3221/2

150mA NanoPower™ LDO Linear Regulator

3221.2002.03.0.9415

Package Information

SOT23-5

SC70JW-8

Θ1

eee

E1 Θ

0.048REF

Dim Millimeters Inches

Min Max Min Max

A 0.95 1.45 0.037 0.057

A1 0.05 0.15 0.002 0.006

A2 0.90 1.30 0.035 0.051

b 0.35 0.50 0.014 0.019

c 0.08 0.20 0.003 0.078

D 2.84 3.00 0.112 0.112

E 1.50 1.70 0.059 0.067

e 1.90 0.0748

H 2.60 3.00 0.102 0.118

L 0.35 0.55 .0137 .0216

S 0.47 0.55 0.019 .0216

S1 .95 0.037

Θ 0° 10° 0° 10°

Dim Millimeters Inches

Min Max Min Max

E 2.10 BSC 0.083 BSC

E1 1.75 2.00 0.069 0.079

L 0.23 0.40 0.009 0.016

A 1.10 0.043

A1 0 0.10 0.004

A2 0.70 1.00 0.028 0.039

D 2.00 BSC 0.079 BSC

e 0.50 BSC 0.020 BSC

b 0.15 0.30 0.006 0.012

c 0.10 0.20 0.004 0.008

Θ 08º08º

Θ1 4º 10º 4º 10º

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AAT3221/2

150mA NanoPower™ LDO Linear Regulator

16 3221.2002.03.0.94

Advanced Analogic Technologies, Inc.

1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086

Phone (408) 524-9684

Fax (408) 524-9689