DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
General Description
Features
The AAT3223 PowerLinear NanoPower low dropout (LDO)
linear regulator is ideal for portable applications where
extended battery life is critical. This device features
extremely low quiescent current, typically 1.1µA. Dropout
voltage is also very low, typically 190mV at 100mA. The
AAT3223 has an enable pin which, when pulled low, will
put the LDO regulator into shutdown mode, removing
power from its load and offering extended power conservation capabilities for portable battery-powered applications. The AAT3223 also has a Power-OK (POK) feature
which monitors the LDO output voltage and will alert the
system if the output falls out of regulation.
•
•
•
•
•
•
•
•
•
The AAT3223 has output short-circuit and over-current
protection. In addition, the device has an over-temperature protection circuit, which will shut down the LDO
regulator during extended over-current events.
The AAT3223 is available in a Pb-free, space-saving 6-pin
SOT23 package and is rated over the -40°C to +85°C
temperature range.
The AAT3223 is similar to the AAT3221 with the exception that it offers the additional Power-OK function
through the POK pin.
•
•
•
•
•
1.1µA Quiescent Current
250mA Output Current
Low Dropout: 190mV (typical)
High Accuracy: ±2%
Current Limit Protection
Over-Temperature Protection
Extremely Low Power Shutdown Mode
Low Temperature Coefficient
Stable Operation With Virtually Any Output Capacitor
Type
Power-OK Signal Output
Active High Enable Pin
4kV ESD
Factory-Programmed Output Voltages
6-pin SOT23 Package
Applications
•
•
•
•
•
•
•
Cellular Phones
Digital Cameras
Handheld Electronics
Notebook Computers
PDAs
Portable Communication Devices
Remote Controls
Typical Application
VIN
IN
AAT3223
1µF
ON/OFF
GND
OUT
EN
100k
POK
GND
VOUT
1µF
POK
GND
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1
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Pin Descriptions
Pin #
Symbol
1
2
3
4
5
IN
GND
OUT
N/C
EN
6
POK
Function
Input pin. It is recommended to bypass this pin with a 1µF capacitor.
Ground connection pin.
Output pin. This pin should be decoupled with a 1µF or larger capacitor.
Not connected.
Enable input. Active high, logic level compatible.
Power-OK output pin. This pin is pulled to ground during a power failure; it is normally high impedance and should have a 100kW pull-up resistor connected to OUT.
Pin Configuration
SOT23-6
(Top View)
2
IN
1
6
POK
GND
2
5
EN
OUT
3
4
N/C
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DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Absolute Maximum Ratings1
Symbol
VIN
VEN
VENIN(MAX)
IOUT
TJ
TLEAD
Description
Input Voltage
EN to GND Voltage
Maximum EN to Input Voltage
Maximum DC Output Current
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec.)
Value
Units
-0.3 to 6
V
0.3
PD/(VIN - VO)
-40 to 150
300
mA
°C
Thermal Information2
Symbol
QJA
PD
Description
Thermal Resistance
Power Dissipation3
Rating
Units
150
667
°C/W
mW
Rating
Units
(VOUT + VDO) to 5.5
-40 to +85
V
°C
Recommended Operating Conditions
Symbol
VIN
T
Description
Input Voltage
Ambient Temperature Range
4
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied.
2. Mounted on a demo board.
3. Derate 6.7mW/°C above 25°C.
4. To calculate minimum input voltage, use the following equation: VIN(MIN) = VOUT(MAX) + VDO(MAX) as long as VIN ³ 2.5V.
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DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Electrical Characteristics
VIN = VOUT(NOM) + 1V, IOUT = 1mA, COUT = 1µF, TA = 25°C, unless otherwise noted.
Symbol
Description
Conditions
VOUT
IOUT
ISC
IQ
IQ-OFF
DVOUT/VOUT
DC Output Voltage Tolerance
Output Current
Short-Circuit Current
Ground Current
Off-Supply Current
Line Regulation
VOUT > 1.2V
VOUT < 0.4V
VIN = 5V, No Load
VIN = 5V, EN = Inactive
VIN = 4.0V to 5.5V
DVOUT/VOUT
VDO
PSRR
TSD
THYS
eN
TC
POK
POKTH
POKHYS
IPOK
VPOK
TPOK
EN
VIH
VIL
IEN(SINK)
Load Regulation
IOUT = 1 to 100mA
Dropout Voltage1, 2
IOUT = 100mA
Power Supply Rejection Ratio
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Output Noise
Output Voltage Temperature Coefficient
100Hz
POK Trip Threshold
Falling
POK
POK
POK
POK
Hysteresis
Off-Current
Low Voltage
Delay
EN Input Threshold High
EN Input Threshold Low
EN Input Leakage
Min
Typ
-2.0
250
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
=
=
=
=
=
=
400
1.1
0.01
0.15
0.7
0.6
0.5
2.8V
3.0V
3.3V
2.8V
3.0V
3.3V
25°C
-40°C to +85°C
190
180
50
140
20
350
80
87.5
86
90.5
Max
Units
2.0
%
mA
2.5
1
0.4
1.20
1.15
1.00
235
225
220
%/V
%
mV
dB
°C
µVRMS
PPM/°C
93.5
95
% VOUT
1.5
VPOK = 5.5V, TA = 25°C
IPOK = 1mA
VOUT Rising
VIN = 2.5V to 5.5V
VON = 5.5V
100
200
1.5
2
0.01
0.5
1
1. VDO is defined as VIN - VOUT when VOUT is 98% of nominal.
2. For VOUT < 2.3V, VDO = 2.5V - VOUT.
4
µA
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nA
mV
ms
V
µA
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Typical Characteristics
Unless otherwise noted, VIN = VOUT + 1V, TA = 25°C, CIN = COUT = 1µF ceramic.
Output Voltage vs. Input Voltage
3.03
3.1
3.02
3
Output Voltage (V)
Output Voltage (V)
Output Voltage vs. Output Current
3.01
-30°C
3
25°C
2.99
80°C
2.98
1mA
2.9
40mA
2.8
2.7
10mA
2.6
2.5
2.97
0
20
40
60
80
2.7
100
Output Current (mA)
Dropout Voltage (mV)
Output Voltage (V)
1mA
10mA
40mA
3
4
4.5
5
300
80°C
200
25°C
-30°C
100
0
5.5
Input Voltage (V)
0
25
50
75
100
125
150
Output Current (mA)
Input Current vs. Input Voltage
PSRR With 10mA Load
60
2.0
1.8
80°C
1.6
1.4
PSRR (dB)
Input (µA) with No Load
3.5
40 0
2.99
3.5
3.3
Dropout Voltage vs. Output Current
3.03
3.01
3.1
Input Voltage (V)
Output Voltage vs. Input Voltage
3.02
2.9
25°C
1.2
1.0
0.8
-30°C
0.6
0.4
40
20
0.2
0.0
0
1
2
3
4
5
0
1.E+01
6
Input Voltage (V)
1.E+02
1.E+03
1.E+04
1.E+05
Frequency (Hz)
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5
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Typical Characteristics
Unless otherwise noted, VIN = VOUT + 1V, TA = 25°C, CIN = COUT = 1µF ceramic.
Line Response With 1mA Load
3.8
20
3.6
Output Voltage (V)
30
10
0
-10
-20
-30
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
4
3.2
3
3
2.8
3.6
3.2
3
2
Output
2.8
Output Voltage (V)
Output Voltage (V)
5
4
1
0
200
400
600
3
80
Output Voltage (V)
Output Voltage (V)
2
Output
2.8
0
200
1
400
600
0
800
0
320
240
Output
3
160
80
2
3
0
-1
0
1
2
Time (ms)
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Output Current (mA)
160
2
6
3
4
Output Current (mA)
Output
2
4
Load Transient - 1mA / 80mA
240
Time (ms)
5
Time (µs)
320
1
0
800
Input
4
0
600
3.2
Load Transient - 1mA / 40mA
-1
400
6
3.4
2.6
-200
0
800
Time (µs)
3
200
Input Voltage (V)
3.8
Input Voltage (V)
Input
6
3.4
2.6
-200
0
Line Response With 100mA Load
3.8
3
1
Time (µs)
Line Response With 10mA Load
3.6
2
Output
Frequency (Hz)
5
Input
3.4
2.6
-200
1.E+06
6
Input Voltage (V)
Noise (dB µV/rtHz)
Noise Spectrum
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Typical Characteristics
Unless otherwise noted, VIN = VOUT + 1V, TA = 25°C, CIN = COUT = 1µF ceramic.
Turn-On With 1mA Load
Power-Up With 1mA Load
OUT (1V/div)
IN (1V/div)
POK (1V/div)
OUT (1V/div)
POK (1V/div)
-1
0
1
2
3
4
EN (1V/div)
-1
5
0
1
2
3
4
5
Time (ms)
Time (ms)
Turn-On With 10mA Load
Power-Up With 10mA Load
IN (1V/div)
OUT (1V/div)
POK (1V/div)
OUT (1V/div)
POK (1V/div)
-1
0
1
2
3
EN (1V/div)
4
5
-1
0
1
2
Time (ms)
3
4
5
Time (ms)
Power-Up With 100mA Load
Turn-On With 100mA Load
IN (1V/div)
OUT (1V/div)
POK (1V/div)
OUT (1V/div)
POK (1V/div)
-1
0
1
2
Time (ms)
3
4
EN (1V/div)
5
-1
0
1
2
3
4
5
Time (ms)
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7
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Typical Characteristics
Unless otherwise noted, VIN = VOUT + 1V, TA = 25°C, CIN = COUT = 1µF ceramic.
Power-Off from 100mA Load
Current Limit Response
OUT (1V/div)
-1
0
1
2
OUT (1V/div)
POK (1V/div)
POK (1V/div)
EN (1V/div)
IOUT (200mA/div)
3
4
-200
5
0
200
400
600
800
Time (ms)
Time (µs)
EN Threshold vs. Input Voltage
EN Threshold (V)
1.50
1.25
-30°C
1.00
0.75
25°C
80°C
0.50
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
8
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1000
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Functional Block Diagram
IN
OUT
Over-Current
Protection
Over-Temperature
Protection
EN
POK
+
Error
Amplifier
-
+
1ms
Delay
91%
VREF
Voltage
Reference
GND
Functional Description
The AAT3223 is intended for LDO regulator applications
where output current load requirements range from no
load to 250mA. The advanced circuit design of the
AAT3223 has been optimized for very low quiescent or
ground current consumption, making it ideal for use in
power management systems in small battery-operated
devices. The typical quiescent current level is just 1.1µA.
The AAT3223 also contains an enable circuit, which has
been provided to shut down the LDO regulator for additional power conservation in portable products. In the
shutdown state, the LDO draws less than 1µA from the
input supply.
The Power-OK function has been incorporated to allow
notification to application circuits when the output voltage falls out of regulation. If the output voltage falls
below the regulation threshold limit, which is compared
to a level set by the internal voltage reference, the POK
pin is pulled to ground through an N-channel MOSFET.
The LDO also demonstrates excellent power supply ripple rejection, and load and line transient response characteristics. The AAT3223 is a high performance LDO
regulator that is especially well suited for circuit applications that are sensitive to load circuit power consumption
and extended battery life.
The LDO regulator output has been specifically optimized
to function with low-cost, low equivalent series resistance
(ESR) ceramic capacitors; however, the design will allow
for operation over a wide range of capacitor types.
The AAT3223 has complete short-circuit and thermal
protection. The integral combination of these two internal protection circuits gives the AAT3223 a comprehensive safety system to guard against extreme adverse
operating conditions. Device power dissipation is limited
to the package type and thermal dissipation properties.
Refer to the Thermal Considerations section of this
datasheet for details on device operation at maximum
output current loads.
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9
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Applications Information
To assure the maximum possible performance is obtained
from the AAT3223, please refer to the following application recommendations.
The total output capacitance required can be calculated
using the following formula:
COUT =
∆I
∙ 15µF
∆V
Input Capacitor
Where:
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
AAT3223 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 closely to the device VIN pin as
practically possible. CIN values greater than 1µF will offer
superior input line transient response and will assist in
maximizing the power supply ripple rejection.
DI = maximum step in output current
DV = maximum excursion in voltage that the load can
tolerate
Ceramic, tantalum, or aluminum electrolytic capacitors
may be selected for CIN, as there is no specific capacitor
ESR requirement. For 250mA LDO regulator output
operation, ceramic capacitors are recommended for CIN
due to their inherent capability over tantalum capacitors
to withstand 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 AAT3223
has been specifically designed to function with very low
ESR ceramic capacitors. Although the device is intended
to operate with these low ESR capacitors, it is stable
over a 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 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.
10
Note that use of this equation results in capacitor values
approximately two to four times the typical value needed
for an AAT3223 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 recommended over all other types of capacitors for use with the
AAT3223. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is
lower cost, has a smaller PCB footprint, and is nonpolarized. 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 incorrectly connected.
Equivalent Series Resistance
ESR is a very important characteristic to consider when
selecting a capacitor. ESR is the internal series resistance associated with a capacitor that 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 C0G materials. NPO and C0G materials generally have tight tolerance and are very stable over temperature. Larger capacitor values are usually composed
of X7R, X5R, Z5U, or Y5V dielectric materials. Large
ceramic capacitors (i.e., greater than 2.2µF) are often
available in low-cost Y5V and Z5U dielectrics. These two
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DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
material types are not recommended for use with LDO
regulators since the capacitor 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
problems for circuit operation and stability. X7R and X5R
dielectrics are much more desirable. The temperature
tolerance of X7R dielectric is better than ±15%.
Capacitor area is another contributor to ESR. Capacitors
that are physically large in size will have a lower ESR
when compared to a smaller sized capacitor of equivalent
material and capacitance 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 datasheets carefully when
selecting capacitors for use with LDO regulators.
Enable Function
The AAT3223 features an LDO regulator enable / disable
function. This pin (EN) is compatible with CMOS logic.
For a logic high signal, the EN control level must be
greater than 2.0V. A logic low signal is asserted when
the voltage on the EN pin falls below 0.5V. For example,
the active high version AAT3223 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 regulator in
a continuously on state; e.g., the active high version
AAT3223 will tie VIN to EN to remain on.
Power-OK Function
The Power-OK (POK) function is a very useful basic
active low error flag. When the AAT3223 output voltage
level is within regulation limits, the POK output pin is a
high impedance and should be tied high to the LDO output through a high value resistor (100kW is a good resistor value for this purpose). An internal comparator has
a reference threshold set to trigger at 10% of the nominal AAT3223 output voltage. If the output voltage level
drops below this preset threshold, the POK function will
become active and turn on an open-drain N-channel
MOSFET to pull the POK output pin to ground. There is
a fixed 1ms delay circuit between the POK comparator
output and the N-channel MOSFET gate. The purpose of
the delay is to prevent a false triggering of the POK output during device turn-on or during very short duration
load transient events. If necessary, additional POK flag
delay can be added by placing a capacitor in parallel with
the POK pull-up resistor. The additional delay time will
be set by the RC time constant, the pull-up resistor, and
parallel capacitor values.
When the AAT3223 is in the shutdown state with the EN
pin low, the POK pin becomes low impedance. The LDO
output will be discharged through the high value POK
pull-up resistor. When entering the shutdown state,
there is no delay associated with the POK output; the
open-drain device turns on immediately.
This offers the added advantage of having a hard application turn-off when the LDO regulator is turned off. This
additional function has no adverse effect on regulator
turn-on time.
Short-Circuit and Thermal Protection
The AAT3223 is protected by both current limit and overtemperature protection circuitry. The internal short-circuit current limit is designed to activate 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 would drop to a level necessary to supply
the current demanded by the load. Under short-circuit or
other over-current operating conditions, the output voltage would drop and the AAT3223’s die temperature
would rapidly increase. 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 circuit will actively turn off the
LDO regulator output pass device to prevent the possibility of over-temperature 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 thermal
protection systems allows the LDO regulator to withstand indefinite short-circuit conditions without sustaining permanent damage.
No-Load Stability
The AAT3223 is designed to maintain output voltage
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 section of
this datasheet for recommended typical output capacitor values.
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11
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Thermal Considerations
and High Output Current Applications
The AAT3223 is designed to deliver a continuous output
load current up to 250mA under normal operating conditions. The limiting characteristic for the maximum output
load safe operating area is essentially package power
dissipation and the internal preset thermal limit of the
device. In order to obtain high operating currents, careful device layout and circuit operating conditions must be
taken into account. The following discussions will assume
the LDO regulator is mounted on a printed circuit board
utilizing the minimum recommended footprint and the
printed circuit board is 0.062-inch thick FR4 material
with one ounce copper.
At any given ambient temperature (TA), the maximum
package power dissipation can be determined by the following equation:
PD(MAX) =
TJ(MAX) - TA
ΘJA
Constants for the AAT3223 are TJ(MAX), the maximum
junction temperature for the device which is 125°C, and
QJA = 150°C/W, the package thermal resistance. Typically,
maximum conditions are calculated at the maximum
operating temperature where TA = 85°C, under normal
ambient conditions TA = 25°C. Given TA = 85°C, 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 AAT3223
is a function of the package power dissipation 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 = 3.0V and TA = 25°C,
IOUT(MAX) < 333.5mA. The output short-circuit protection
threshold is set between 300mA and 450mA. If the output
load current were to exceed 333.5mA or if the ambient
temperature were to increase, the internal die temperature would increase. If the condition remained constant
and the short-circuit protection did not activate, there
would be a potential damage hazard to the LDO regulator
since the thermal protection circuit will only activate after
a short-circuit event occurs on the LDO regulator output.
12
To determine the maximum input voltage for a given
load current, refer to the following equation. This calculation accounts for the total power dissipation of the LDO
regulator, including that caused by ground current.
PD(MAX) = (VIN - VOUT)IOUT + (VIN · IGND)
This formula can be solved for VIN to determine the maximum input voltage.
VIN(MAX) =
PD(MAX) + (VOUT ∙ IOUT)
IOUT + IGND
The following is an example for an AAT3223 set for a
3.0V output:
VOUT
= 3.0V
IOUT
= 150mA
IGND
= 1.1µA
VIN(MAX) =
667mW + (3.0V ∙ 150mA)
150mA + 1.1µA
= 7.45V
From the discussion above, PD(MAX) was determined to
equal 667mW at TA = 25°C.
Thus, the AAT3223 can sustain a constant 3.0V output at
a 150mA load current as long as VIN is ≤7.45V at an
ambient temperature of 25°C. 5.5V is the maximum
input operating voltage for the AAT3223, 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 following is an
example for an AAT3223 set for a 3.0V output at 85°C:
VOUT
= 3.0V
IOUT
= 150mA
IGND
= 1.1µA
VIN(MAX) =
267mW + (3.0V ∙ 150mA)
150mA + 1.1µA
= 4.78V
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DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
From the discussion above, PD(MAX) was determined to
equal 267mW at TA = 85°C.
IGND
= 1.1µA
IOUT
= 150mA
VIN
= 5.0V
VOUT = 3.0V
%DC =
PD(MAX)
(VIN - VOUT) ∙ IOUT + (VIN ∙ IGND)
267mW
%DC =
(5.0V - 3.0V) ∙ 150mA + (5.0V ∙ 1.1µA)
4
250mA
3.5
Voltage Drop (V)
For example, an application requires VIN = 5.0V while VOUT
= 3.0V at a 150mA load and TA = 85°C. VIN is greater than
4.78V, which is the maximum safe continuous input level
for VOUT = 3.0V 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:
(VOUT = 3.0V @ 25°C)
3
2.5
300mA
2
1.5
1
0.5
0
0
10
20
30
50
60
70
80
90
100
Device Duty Cycle vs. VDROP
(VOUT = 3.0V @ 50°C)
4
200mA
3.5
3
2.5
2
300mA
1.5
250mA
1
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
%DC = 89%
Device Duty Cycle vs. VDROP
PD(MAX) was assumed to be 267mW.
(VOUT = 3.0V @ 85°C)
For a 150mA output current and a 2V drop across the
AAT3223 at an ambient temperature of 85°C, the maximum on-time duty cycle for the device would be 89%.
4
Voltage Drop (V)
The following family of curves shows the safe operating
area for duty-cycled operation from ambient room temperature to the maximum operating level.
40
Duty Cycle (%)
Voltage Drop (V)
Higher input-to-output voltage differentials can be
obtained with the AAT3223, 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.
Device Duty Cycle vs. VDROP
200mA
3.5
100mA
150mA
3
2.5
2
1.5
250mA
1
300mA
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
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13
DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
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 calculate the power dissipation at the nominal continuous level, then factor in the addition power dissipation
due to the short duration, high-current peaks.
For example, a 2.8V system using a AAT3223IGU-2.8-T1
operates at a continuous 100mA load current level and
has short 250mA 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 and then multiplied by the duty cycle to conclude the actual power dissipation over time.
PD(MAX) = (VIN - VOUT)IOUT + (VIN · IGND)
PD(100mA) = (5.0V - 2.8V)100mA + (5.0V · 1.1µA)
PD(100mA) = 225.5mW
PD(91.8%D/C) = %DC · PD(100mA)
PD(91.8%D/C) = 0.918 · 225.5mW
PD(91.8%D/C) = 207mW
The power dissipation for a 100mA load occurring for
91.8% of the duty cycle will be 207mW. Now the power
dissipation for the remaining 8.2% of the duty cycle at
the 150mA load can be calculated:
14
PD(MAX) = (VIN - VOUT)IOUT + (VIN · IGND)
PD(250mA) = (5.0V - 2.8V)250mA + (5.0V · 1.1µA)
PD(250mA) = 550mW
PD(8.2%D/C) = %DC · PD(250mA)
PD(8.2%D/C) = 0.082 · 550mW
PD(8.2%D/C) = 45.1mW
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(250mA)
PD(total) = 207mW + 45.1mW
PD(total) = 252.1mW
The maximum power dissipation for the AAT3223 operating at an ambient temperature of 85°C is 267mW. The
device in this example will have a total power dissipation
of 252.1mW. 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
AAT3223 LDO regulator, careful attention should be given
to the printed circuit board layout. If grounding connections are not properly 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 maximum performance with
the AAT3223, the ground pin connection should then be
made directly back to the ground or common of the
source power supply. 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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3223
250mA NanoPowerTM LDO Linear Regulator with Power-OK
Ordering Information
Output Voltage
Enable
Package
Marking1
Part Number (Tape and Reel)2
3.0V
3.3V
Active high
Active high
SOT23-6
SOT23-6
GEXYY
GQXYY
AAT3223IGU-3.0-T1
AAT3223IGU-3.3-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
SOT23-6
2.85 ± 0.15
1.90 BSC
2.80 ± 0.20
0.15 ± 0.07
4° ± 4°
10° ± 5°
All dimensions in millimeters.
1.20 ± 0.25
1.10 ± 0.20
0.075 ± 0.075
1.575 ± 0.125
0.95 BSC
0.40 ± 0.10 × 6
0.60 REF
0.45 ± 0.15
GAUGE PLANE
0.10 BSC
1. XYY = assembly and date code.
2. Sample stock is generally held on all part numbers listed in BOLD.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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