Analogic AAT3223 250ma nanopowerâ ¢ ldo linear regulator with power-ok Datasheet

AAT3223
250mA NanoPower™ 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 PowerOK (POK) feature which monitors the LDO output
voltage and will alert the system if the output falls
out of regulation.
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The AAT3223 has output short-circuit and overcurrent protection. In addition, the device has an
over-temperature protection circuit, which will shut
down the LDO regulator during extended over-current events.
PowerLinear™
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
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.
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The AAT3223 is similar to the AAT3221 with the
exception that it offers the additional Power-OK
function through the POK pin.
Cellular Phones
Digital Cameras
Handheld Electronics
Notebook Computers
PDAs
Portable Communication Devices
Remote Controls
Typical Application
VIN
IN
AAT3223
1µF
ON/OFF
GND
3223.2006.03.1.5
OUT
EN
100k
POK
GND
VOUT
1µF
POK
GND
1
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
Pin Descriptions
Pin #
Symbol
Function
1
IN
2
GND
Ground connection pin.
3
OUT
Output pin. This pin should be decoupled with a 1µF or larger capacitor.
4
N/C
Not connected.
5
EN
Enable input. Active high, logic level compatible.
6
POK
Input pin. It is recommended to bypass this pin with a 1µF capacitor.
Power-OK output pin. This pin is pulled to ground during a power failure; it
is normally high impedance and should have a 100kΩ 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
3223.2006.03.1.5
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
Absolute Maximum Ratings1
TA = 25°C, unless otherwise noted.
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
-0.3 to 6
0.3
PD/(VIN - VO)
-40 to 150
300
V
V
V
mA
°C
°C
Rating
Units
150
667
°C/W
mW
Rating
Units
(VOUT + VDO) to 5.5
-40 to +85
V
°C
Thermal Information2
Symbol
ΘJA
PD
Description
Thermal Resistance
Power Dissipation3
Recommended Operating Conditions
Symbol
VIN
T
Description
4
Input Voltage
Ambient Temperature Range
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. Only one Absolute Maximum Rating should be applied at any one time.
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 ≥ 2.5V.
3223.2006.03.1.5
3
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
Electrical Characteristics
VIN = VOUT(NOM) + 1V, IOUT = 1mA, COUT = 1µF, TA = 25°C, unless otherwise noted.
Symbol
VOUT
IOUT
ISC
IQ
IQ-OFF
∆VOUT/VOUT
∆VOUT/VOUT
VDO
PSRR
TSD
THYS
eN
TC
Description
DC Output Voltage Tolerance
Output Current
Short-Circuit Current
Ground Current
Off-Supply Current
Line Regulation
Load Regulation
Dropout Voltage1, 2
Power Supply Rejection Ratio
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
Output Noise
Output Voltage Temperature
Coefficient
Conditions
Min
VOUT > 1.2V
VOUT < 0.4V
VIN = 5V, No Load
VIN = 5V, EN = Inactive
VIN = 4.0V to 5.5V
VOUT
VOUT
VOUT
IL = 1 to 100mA
VOUT
VOUT
VOUT
VOUT
VOUT
IOUT = 100mA
VOUT
VOUT
VOUT
100Hz
Typ
-2.0
250
0.15
=
=
=
=
=
=
=
=
=
=
=
1.8V
2.7V
2.8V
2.85V
3.0V
3.3V
2.7V
2.8V
2.85V
3.0V
3.3V
400
1.1
0.01
0.4
1.0
0.7
0.7
0.7
0.6
0.5
200
190
190
190
180
50
Max
Units
2.0
%
mA
mA
µA
µA
2.5
1
%/V
1.65
1.25
1.20
1.20
1.15
1.00
240
235
230
225
220
%
mV
dB
140
°C
20
°C
350
µVRMS
80
PPM/°C
POK
POKTH
POKHYS
IPOK
VPOK
TPOK
EN
VIH
VIL
IEN(SINK)
25°C
-40°C to +85°C
POK Trip Threshold
Falling
POK
POK
POK
POK
VPOK = 5.5V, TA = 25°C
IPOK = 1mA
VOUT Rising
Hysteresis
Off-Current
Low Voltage
Delay
EN Input Threshold High
EN Input Threshold Low
EN Input Leakage
87.5
86
90.5
93.5
95
1.5
VIN = 2.5V to 5.5V
VIN = 2.5V to 5.5V
VON = 5.5V
100
200
1.5
2
0.01
0.5
1
% of
VOUT
nA
mV
ms
V
µA
1. VDO is defined as VIN - VOUT when VOUT is 98% of nominal.
2. For VOUT < 2.3V, VDO = 2.5V - VOUT.
4
3223.2006.03.1.5
AAT3223
250mA NanoPower™ 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
2.9
Output Current (mA)
Dropout Voltage (mV)
Output Voltage (V)
3.5
Dropout Voltage vs. Output Current
3.03
1mA
10mA
3.01
40mA
3
40 0
300
80°C
200
25°C
-30°C
100
0
2.99
3.5
4
4.5
5
0
5.5
25
50
75
100
125
150
Output Current (mA)
Input Voltage (V)
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
3.3
Input Voltage (V)
Output Voltage vs. Input Voltage
3.02
3.1
25°C
1.2
1.0
0.8
0.6
-30°C
40
20
0.4
0.2
0.0
0
1
2
3
4
Input Voltage (V)
3223.2006.03.1.5
5
6
0
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
Frequency (Hz)
5
AAT3223
250mA NanoPower™ 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
1.E+02
1.E+03
1.E+04
1.E+05
4
3.2
3
3
2
Output
2.8
1
0
6
3.8
5
3.6
3.4
4
3.2
3
3
2
Output
2.8
1
0
200
400
600
5
Input
3.4
4
3.2
3
3
2
Output
2.8
2.6
-200
0
800
6
1
0
0
800
600
80
2
0
2
3
Output Voltage (V)
160
320
240
Output
3
160
80
2
Output Current (mA)
Output
3
4
Output Current (mA)
240
Time (ms)
400
Load Transient - 1mA / 80mA
320
1
200
Time (µs)
4
0
Input Voltage (V)
Input
Load Transient - 1mA / 40mA
Output Voltage (V)
0
800
600
Line Response With 100mA Load
Time (µs)
6
400
Line Response With 10mA Load
3.6
-1
200
Time (µs)
Input Voltage (V)
Output Voltage (V)
3.4
Frequency (Hz)
3.8
2.6
-200
5
Input
2.6
-200
1.E+06
Output Voltage (V)
-30
1.E+01
6
Input Voltage (V)
Noise (dB µV/rt Hz )
Noise Spectrum
0
-1
0
1
2
3
Time (ms)
3223.2006.03.1.5
AAT3223
250mA NanoPower™ 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
Power-Up With 10mA Load
Turn-On With 10mA Load
IN (1V/div)
OUT (1V/div)
POK (1V/div)
OUT (1V/div)
POK (1V/div)
0
1
2
3
EN (1V/div)
4
5
-1
0
1
2
3
4
Time (ms)
Time (ms)
Power-Up With 100mA Load
Turn-On With 100mA Load
IN (1V/div)
POK (1V/div)
POK (1V/div)
0
1
2
Time (ms)
3223.2006.03.1.5
3
4
5
OUT (1V/div)
OUT (1V/div)
-1
5
Time (ms)
Time (ms)
-1
4
EN (1V/div)
5
-1
0
1
2
3
4
5
Time (ms)
7
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
Typical Characteristics
Unless otherwise noted, VIN = VOUT + 1V, TA = 25°C, CIN = COUT = 1µF ceramic.
Current Limit Response
Power-Off from 100mA Load
OUT (1V/div)
-1
0
1
2
OUT (1V/div)
POK (1V/div)
POK (1V/div)
EN (1V/div)
IOUT (200mA/div)
3
4
5
-200
0
200
400
600
800
1000
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
3223.2006.03.1.5
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
Functional Block Diagram
IN
OUT
Over-Current
Protection
Over-Temperature
Protection
POK
+
Error
Amplifier
EN
-
-
+
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.
3223.2006.03.1.5
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.
9
AAT3223
250mA NanoPower™ 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.
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 calculated using the following formula:
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 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.
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.
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 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
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
10
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 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 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.
3223.2006.03.1.5
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
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 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.
resistor (100kΩ 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.
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
3223.2006.03.1.5
Short-Circuit and Thermal Protection
The AAT3223 is protected by both current limit and
over-temperature 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
11
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
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 noload 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.
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 ΘJA = 150°C/W, the package thermal
12
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 = 2.8V and TA =
25°C, IOUT(MAX) < 267mA. The output short-circuit
protection threshold is set between 300mA and
450mA. If the output load current were to exceed
267mA 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.
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 x IGND)
This formula can be solved for VIN to determine the
maximum input voltage.
VIN(MAX) =
PD(MAX) + (VOUT × IOUT)
IOUT + IGND
3223.2006.03.1.5
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
The following is an example for an AAT3223 set for
a 2.8V output:
VOUT
= 2.9V
IOUT
= 250mA
IGND
= 1.1µA
VIN(MAX) =
667mW + (2.8V × 150mA)
150mA + 1.1µA
VIN(MAX) = 9.11V
From the discussion above, PD(MAX) was determined to equal 667mW at TA = 25°C.
Thus, the AAT3223 can sustain a constant 2.8V
output at a 150mA load current as long as VIN is
≤9.11V 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 2.8V
output at 85°C:
VOUT
= 2.9V
IOUT
= 150mA
IGND
= 1.1µA
VIN(MAX) =
267mW + (2.8V × 150mA)
150mA + 1.1µA
VIN(MAX) = 4.58V
From the discussion above, PD(MAX) was determined to equal 267mW at TA = 85°C.
3223.2006.03.1.5
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.
For example, an application requires VIN = 5.0V
while VOUT = 2.8V at a 150mA load and TA = 85°C.
VIN is greater than 4.58V, which is the maximum
safe continuous input level for VOUT = 2.8V 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:
IGND = 1.1µA
IOUT
= 150mA
VIN
= 5.0V
VOUT = 2.8V
%DC = 100
PD(MAX)
(VIN - VOUT)IOUT + (VIN × IGND)
%DC = 100
267mW
(5.0V - 2.8V)150mA + (5.0V × 1.1µA)
%DC = 80.9%
PD(MAX) was assumed to be 267mW.
For a 150mA output current and a 2.2V drop across
the AAT3223 at an ambient temperature of 85°C,
the maximum on-time duty cycle for the device
would be 80.9%.
The following family of curves shows the safe
operating area for duty-cycled operation from
ambient room temperature to the maximum operating level.
13
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
+
Device Duty Cycle vs. VDROP
High Peak Output Current Applications
(VDROP = 2.8V @ 25°C)
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.
4
250mA
Voltage Drop (V)
3.5
3
2.5
300mA
2
1.5
1
0.5
0
0
10
20
30
40
50
60
70
80
90
100
Duty Cycle (%)
First, the current duty cycle percentage must be
calculated:
Device Duty Cycle vs. VDROP
(VDROP = 2.8V @ 50°C)
4
200mA
Voltage Drop (V)
3.5
% Peak Duty Cycle: X/100 = 378ms/4.61ms
% Peak Duty Cycle = 8.2%
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 (%)
(VDROP = 2.8V @ 85°C)
200mA
100mA
150mA
3
= (VIN - VOUT)IOUT + (VIN x IGND)
= (5.0V - 2.8V)100mA + (5.0V x 1.1µA)
= 225.5mW
PD(91.8%D/C) = %DC x PD(100mA)
PD(91.8%D/C) = 0.918 x 225.5mW
PD(91.8%D/C) = 207mW
4
3.5
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)
PD(100mA)
PD(100mA)
Device Duty Cycle vs. VDROP
Voltage Drop (V)
For example, a 2.8V system using a AAT3223IGU2.8-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.
2.5
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:
2
1.5
250mA
1
300mA
0.5
0
0
10
20
30
40
50
60
Duty Cycle (%)
70
80
90
100
PD(MAX)
PD(250mA)
PD(250mA)
= (VIN - VOUT)IOUT + (VIN x IGND)
= (5.0V - 2.8V)250mA + (5.0V x 1.1µA)
= 550mW
PD(8.2%D/C) = %DC x PD(250mA)
PD(8.2%D/C) = 0.082 x 550mW
PD(8.2%D/C) = 45.1mW
14
3223.2006.03.1.5
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
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.
3223.2006.03.1.5
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.
15
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
Ordering Information
Output Voltage
Enable
1.8V
2.7V
2.8V
2.85V
3.0V
3.3V
Active
Active
Active
Active
Active
Active
Package
Marking1
Part Number (Tape and Reel)2
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
EGXYY
GGXYY
EHXYY
GFXYY
GEXYY
GQXYY
AAT3223IGU-1.8-T1
AAT3223IGU-2.7-T1
AAT3223IGU-2.8-T1
AAT3223IGU-2.85-T1
AAT3223IGU-3.0-T1
AAT3223IGU-3.3-T1
high
high
high
high
high
high
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
SOT23-6
2.85 ± 0.15
1.90 BSC
2.80 ± 0.20
1.20 ± 0.25
0.15 ± 0.07
4° ± 4°
1.10 ± 0.20
0.075 ± 0.075
1.575 ± 0.125
0.95 BSC
10° ± 5°
0.40 ± 0.10 × 6
0.60 REF
0.45 ± 0.15
GAUGE PLANE
0.10 BSC
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on all part numbers listed in BOLD.
16
3223.2006.03.1.5
AAT3223
250mA NanoPower™ LDO
Linear Regulator with Power-OK
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights,
or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold
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830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
3223.2006.03.1.5
17
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