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300mA MicroPowerTM LDO with PowerOK General Description
The AAT3237 MicroPowerTM Low Dropout Linear Regulator is ideally suited for portable applications where low noise, extended battery life and small size are critical. The AAT3237 has been specifically designed for low output noise performance, fast transient response and high power supply rejection ratio (PSRR). Other features include low quiescent current, typically 70A, and low dropout voltage which is typically less than 400mV at full output current. The device is output short circuit protected and has a thermal shutdown circuit for additional protection under extreme conditions. The AAT3237 also features a low-power shutdown mode for extended battery life. A Power-OK opendrain output signals when VOUT is in regulation. The AAT3237 is available in a space saving 6-pin SOT23 or 8-pin SC70JW package in 13 factory programmed voltages of 1.2V, 1.5V, 1.8V, 2.0V, 2.3V, 2.5V, 2.7V, 2.8V, 2.85V, 2.9V, 30.V, 3.3V, or 3.5V.
AAT3237
Features
* * * * * * * * * * * * * *
PowerLinear TM SmartSwitchTM
Low Dropout - 400mV at 300mA Guaranteed 300mA Output High accuracy 1.5% 70A Quiescent Current High Power Supply Ripple Rejection PowerOK (POK) Output Fast line and load transient response Short circuit protection Over-Temperature protection Uses Low ESR ceramic capacitors Shutdown mode for longer battery life Low temperature coefficient 13 Factory programmed output voltages SOT23 6-pin or SC70JW 8-pin package
Applications
* * * * * * Cellular Phones Notebook Computers Desktop Computers Portable Communication Devices Personal Portable Electronics Digital Cameras
Typical Application
VIN IN OUT VOUT
AAT3237
ON/OFF EN GND 1F 2.2F POK
POK
GND
GND
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300mA MicroPowerTM LDO with PowerOK Pin Descriptions
Pin #
SOT23-6 SC70JW-8
AAT3237
Symbol
IN GND EN
Function
Input voltage pin - should be decoupled with 1F or greater capacitor. Ground connection pin Enable pin - this pin should not be left floating. When pulled low the PMOS pass transistor turns off and all internal circuitry enters low-power mode, consuming less than 1A. Power-OK Output. This open-drain output is low when OUT is out of regulation. Connect a pull up resistor from POK to OUT. Output pin - should be decoupled with 2.2F ceramic capacitor.
1 2, 5 3
5, 6 8 7
4 6
1 2, 3, 4
POK OUT
Pin Configuration
SOT23-6 (Top View) SC70JW-8 (Top View)
IN GND EN
1
6
OUT GND POK
2
5
3
4
POK OUT OUT OUT
1 2 3 4
8 7 6 5
GND EN IN IN
2
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300mA MicroPowerTM LDO with PowerOK Absolute Maximum Ratings
Symbol
VIN, POK VENIN(MAX) IOUT TJ TLEAD
AAT3237
(TA=25C unless otherwise noted) Value
6 0.3 PD/(VIN-VO) -40 to 150 300
Description
Input Voltage, POK Maximum EN to Input Voltage DC Output Current Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec)
Units
V V mA C C
Note: 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.
Thermal Information
Symbol
JA PD
Description
Maximum Thermal Resistance1 (SOT23-6, SC70JW-8) Maximum Power Dissipation1 (SOT23-6, SC70JW-8)
Rating
150 667
Units
C/W mW
Note 1: Mounted on a demo board.
Recommended Operating Conditions
Symbol
VIN T
Description
Input Voltage 2 Ambient Temperature Range
Rating
(VOUT+VDO) to 5.5 -40 to +85
Units
V C
Note 2: To calculate minimum input voltage, use the following equation: VIN(MIN) = VOUT(MAX) + VDO(MAX) as long as VIN 2.5V.
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300mA MicroPowerTM LDO with PowerOK Electrical Characteristics
(VIN=VOUT(NOM)+1V for VOUT options greater than 1.5V. VIN= 2.5V for VOUT1.5V. IOUT=1mA, COUT=2.2F, CIN=1f, TA= -40 to 85C unless otherwise noted. Typical values are TA=25C) Symbol
VOUT IOUT VDO ISC IQ ISD VOUT/VOUT*VIN VOUT(line) VOUT(load) VEN(L) VEN(H) IEN VPOK VPOKHYS VPOK(OL) IPOK PSRR TSD THYS eN TC
AAT3237
Description
Output Voltage Tolerance Output Current Dropout Voltage 1, 2 Short Circuit Current Ground Current Shutdown Current Line Regulation 3 Dynamic Line Regulation Dynamic Load Regulation Enable Threshold Low Enable Threshold High Leakage Current on Enable Pin POK Trip Threshold POK Hysteresis POK Output Voltage Low POK Output Leakage Current Power Supply Rejection Ratio
Conditions
IOUT = 1mA to 300mA
Min Typ Max
TA=25C -1.5 TA=-40 to 85C -2.5 300 400 600 70 1.5 2.5 600 125 1 0.09 5 60 0.6 1.5
Units
% % mA mV mA A A %/V mV mV V V A % of VOUT % of VOUT V A dB C C Vrms/rtHz ppm/C
VOUT > 1.2V IOUT = 300mA VOUT < 0.4V VIN = 5V, No load, EN = VIN VIN = 5V, EN = 0V VIN = VOUT + 1 to 5.0V
VIN=VOUT+1V to VOUT+2V, IOUT=300mA, TR/TF =2s IOUT = 1mA to 300mA, TR<5s
VEN = 5V VOUT rising, TA=25C ISINK = 1mA VPOK < 5.5V, VOUT in regulation 1 kHz IOUT=10mA 10kHz 1MHz
90
94 1
1 98 0.4 1
Over Temp Shutdown Threshold Over Temp Shutdown Hysteresis Output Noise Noise Power BW = 300Hz-50kHz Output Voltage Temp. Coeff.
65 45 42 145 12 250 22
Note 1: VDO is defined as VIN - VOUT when VOUT is 98% of nominal. Note 2: For VOUT < 2.1V, VDO = 2.5V - VOUT. Note 3: CIN = 10F
4
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300mA MicroPowerTM LDO with PowerOK Typical Characteristics
AAT3237
(Unless otherwise noted, VIN = 5V, TA = 25C) Dropout Voltage vs. Temperature
3.20
Dropout Characteristics
540
Dropout Voltage (mV)
480 420 360 300 240 180 120 60 0
IL = 300mA
V OUT (V)
3.00 2.80 2.60 2.40 2.20
IOUT = 0mA
IL = 150mA
IL = 100mA
IOUT = 300mA IOUT = 150mA IOUT = 10mA
2.80
IOUT = 100mA IOUT = 50mA
IL = 50mA
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120
2.00 2.70
2.90
3.00
3.10
3.20
3.30
Temperature (C)
VIN (V)
Dropout Voltage vs. Output Current
500 450 90.00 80.00 70.00 60.00
Ground Current vs. Input Voltage
Dropout Voltage (mV)
400
IGND (A)
350 300 250 200 150 100 50 0 0 50 100 150 200 250 300
85C 25C -40C
50.00 40.00 30.00 20.00 10.00 0.00 2 2.5 3
IOUT=300mA IOUT=0mA IOUT=150mA IOUT=50mA
IOUT=10mA
3.5
4
4.5
5
Output Current (mA)
VIN (V)
Quiescent Current vs. Temperature
100
Output Voltage vs. Temperature
1.203 1.202
Quiescent Current (A)
90
Output Voltage (V)
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120
80 70 60 50 40 30 20 10 0
1.201 1.200 1.199 1.198 1.197 1.196 -40 -30 -20 -10
0
10 20
30
40
50 60
70 80
90 100
Temperature (C)
Temperature (C)
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300mA MicroPowerTM LDO with PowerOK Typical Characteristics
AAT3237
(Unless otherwise noted, VIN = 5V, TA = 25C) Turn On Time and POK Delay Turn Off Time with POK Delay
VENABLE (2V/div) VEN (2V/div) VOUT (500mV/div) VPOK (500mV/div) VPOK (2V/div) VOUT (2V/div) Time (10s/div) Time (200s/div)
Line Transient Response
VIN (2V/div)
6 5 4 3.25
POK Output Response
VIN
3.20 3.15 3.10 3.05 3.00
VOUT (2V/div) V OUT (V)
V IN (V)
3 2 1 0 -1 -2
VOUT
2.95 2.90 2.85
VPOK (1V/div)
Time (200s/div.)
Time (100 s/div)
Load Transient Response
2.90 2.85 500 400 300 200 100 3.00 2.90 2.80 2.70
Load Transient Response 300mA
800 700
VOUT
V OUT (V)
VOUT
600 500 400 300 200
2.80 2.75 2.70 2.65 2.60
VOUT (V)
IOUT (mA)
IOUT (mA)
2.60 2.50 2.40 2.30 2.20 2.10
IOUT
0 -100
IOUT
100 0 -100
Time (100 s/div)
10 s/div
6
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300mA MicroPowerTM LDO with PowerOK Typical Characteristics
AAT3237
(Unless otherwise noted, VIN = 5V, TA = 25C) Over Current Protection
1200 1000 800
AAT3237 Self Noise
Noise Amplitude (V/rtHz)
10
IOUT (mA)
600 400 200 0 -200
1
0.1
Time (20 ms/div)
0.01 0.01
0.1
1
10
100
1000
Frequency (kHz)
VEN(H) and V EN(L) vs. VIN
1.250 1.225 1.200
VEN (V)
1.175 1.150 1.125 1.100 1.075 1.050 2.5
VEN(H)
VEN(L)
3.0
3.5
4.0
4.5
5.0
5.5
VIN (V)
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300mA MicroPowerTM LDO with PowerOK Functional Block Diagram
IN
Over-Current Protection Over-Temperature Protection
AAT3237
OUT
Error Amplifier
EN
POK
Voltage Reference 94%
GND
Functional Description
The AAT3237 is intended for LDO regulator applications where output current load requirements range from no load to 300mA. The advanced circuit design of the AAT3237 provides excellent transient response and fast turn-on ability. The LDO regulator output has been specifically optimized to function with low cost, low ESR ceramic capacitors. However, the design will allow for operation over a wide range of capacitor types. The AAT3237 has an integrated Power-OK comparator which indicates when the output is out of regulation.
The device enable circuit is provided to shutdown the LDO regulator for power conservation in portable products. The enable circuit has an additional output capacitor discharge circuit to assure sharp application circuit turn off upon device shutdown. This LDO regulator has complete short circuit and thermal protection. The integral combination of these two internal protection circuits give the AAT3237 a comprehensive safety system during extreme adverse operating conditions. Device power dissipation is limited to the package type and thermal dissipation properties. Refer to the thermal considerations discussion in the section for details on device operation at maximum output current loads.
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300mA MicroPowerTM LDO with PowerOK Applications Information
To assure the maximum possible performance is obtained from the AAT3237, please refer to the following application recommendations.
AAT3237
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3237. 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 not prone to incorrect connection damage. Equivalent Series Resistance (ESR): ESR is a very important characteristic to consider when selecting a capacitor. ESR is the internal series resistance associated with a capacitor, which includes lead resistance, internal connections, size and area, material composition and ambient 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 0.1F are typically made from NPO or COG materials. NPO and COG materials are typically tight tolerance very stable over temperature. Larger capacitor values are typically composed of X7R, X5R, Z5U and Y5V dielectric materials. Large ceramic capacitors, typically greater then 2.2F are often available in the low cost Y5V and Z5U dielectrics. These two material types are not recommended for use with LDO regulators since the capacitor tolerance can vary more than 50% over the operating temperature range of the device. A 2.2F Y5V capacitor could be reduced to 1F over temperature, this could cause problems for circuit operation. X7R and X5R dielectrics are much more desirable. The temperature tolerance of X7R dielectric is better than 15%. Capacitor area is another contributor to ESR. Capacitors which are physically large in size will have a lower ESR when compared to a smaller sized capacitor of an equivalent material and capacitance value. These larger devices can improve circuit transient response when compared to an equal value capacitor in a smaller package size.
Input Capacitor
Typically a 1F or larger capacitor is recommended for CIN in most applications. A CIN capacitor is not required for basic LDO regulator operation. However, if the AAT3237 is physically located more than 3 centimeters from an input power source, a CIN capacitor will be needed for stable operation. CIN should be located as close to the device VIN pin as practically possible. CIN values greater than 1F will offer superior input line transient 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. However, for 300mA 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 AAT3237 has been specifically designed to function with very low ESR ceramic capacitors. For best performance, ceramic capacitors are recommended. Typical output capacitor values for maximum output current conditions range from 1F to 10F. Applications utilizing the exceptionally low output noise and optimum power supply ripple rejection characteristics of the AAT3237 should use 2.2F or greater for COUT. If desired, COUT may be increased without limit. In low output current applications where output load is less then 10mA, the minimum value for COUT can be as low as 0.47F.
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300mA MicroPowerTM LDO with PowerOK Applications Information
Consult capacitor vendor data sheets carefully when selecting capacitors for LDO regulators. 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 145C trip point. The combination and interaction between the short circuit and thermal protection systems allow the LDO regulator to withstand indefinite short circuit conditions without sustaining permanent damage.
AAT3237
POK Output
The AAT 3237 features an integrated Power-OK comparator which can be used as an error flag. The POK open-drain output goes low when OUT is 6% below its nominal regulation voltage. Connect a pull-up resistor from POK to OUT.
No-Load Stability
The AAT3237 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.
Enable Function
The AAT3237 features an LDO regulator enable/ disable function. This pin (EN) is active high and is compatible with CMOS logic. To assure the LDO regulator will switch on, the EN turn on control level must be greater than 2.0 volts. The LDO regulator will go into the disable shutdown mode when the voltage on the EN pin falls below 0.6 volts. If the enable function is not needed in a specific application, it may be tied to VIN to keep the LDO regulator in a continuously on state. When the LDO regulator is in the shutdown mode, an internal 1.5k resistor is connected between VOUT and GND. This is intended to discharge COUT when the LDO regulator is disabled. The internal 1.5k has no adverse effect on device turn on time.
Reverse Output to Input Voltage Conditions and Protection
Under normal operating conditions a parasitic diode exists between the output and input of the LDO regulator. The input voltage should always remain greater then the output load voltage maintaining a reverse bias on the internal parasitic diode. Conditions where VOUT might exceed VIN should be avoided since this would forward bias the internal parasitic diode and allow excessive current flow into the VOUT pin possibly damaging the LDO regulator. In applications where there is a possibility of VOUT exceeding VIN for brief amounts of time during normal operation, the use of a larger value CIN capacitor is highly recommended. A larger value of CIN with respect to COUT will effect a slower CIN decay rate during shutdown, thus preventing VOUT from exceeding VIN. In applications where there is a greater danger of VOUT exceeding VIN for extended periods of time, it is recommended to place a Schottky diode across VIN to VOUT (connecting the cathode to VIN and anode to VOUT). The Schottky diode forward voltage should be less than 0.45 volts.
Short Circuit Protection
The AAT3237 contains an internal short circuit protection circuit that will trigger when the output load current exceeds the internal threshold limit. Under short circuit conditions the output of the LDO regulator will be current limited until the short circuit condition is removed from the output or LDO regulator package power dissipation exceeds the device thermal limit.
Thermal Protection
The AAT3237 has an internal thermal protection circuit which will turn on when the device die temperature exceeds 145C. The internal thermal protection circuit will actively turn off the LDO regulator output
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300mA MicroPowerTM LDO with PowerOK Ordering Information
Output Voltage 1.2V 1.5V 1.8V 2.0V 2.3V 2.5V 2.7V 2.8V 2.85V 2.9V 3.0V 3.3V 3.5V 1.2V 1.5V 1.8V 2.0V 2.3V 2.5V 2.7V 2.8V 2.85V 2.9V 3.0V 3.3V 3.5V Package SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 SC70JW-8 FBXYY GRXYY GSXYY GMXYY HRXYY Marking1 EJXYY Part Number (Tape and Reel) AAT3237IGU-1.2-T1 AAT3237IGU-1.5-T1 AAT3237IGU-1.8-T1 AAT3237IGU-2.0-T1 AAT3237IGU-2.3-T1 AAT3237IGU-2.5-T1 AAT3237IGU-2.7-T1 AAT3237IGU-2.8-T1 AAT3237IGU-2.85-T1 AAT3237IGU-2.9-T1 AAT3237IGU-3.0-T1 AAT3237IGU-3.3-T1 AAT3237IGU-3.5-T1 AAT3237IJS-1.2-T1 AAT3237IJS-1.5-T1 AAT3237IJS-1.8-T1 AAT3237IJS-2.0-T1 AAT3237IJS-2.3-T1 AAT3237IJS-2.5-T1 AAT3237IJS-2.7-T1 AAT3237IJS-2.8-T1 AAT3237IJS-2.85-T1 AAT3237IJS-2.9-T1 AAT3237IJS-3.0-T1 AAT3237IJS-3.3-T1 AAT3237IJS-3.5-T1
AAT3237
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
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300mA MicroPowerTM LDO with PowerOK Package Information
SOT23-6
2.85 0.15 1.90 BSC 0.95 BSC
AAT3237
1.575 0.125
1.10 0.20
2.80 0.20 1.20 0.25
0.075 0.075
0.15 0.07 4 4
GAUGE PLANE
10 5 0.40 0.10 x 6
0.60 REF
0.45 0.15
0.10 BSC
12
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300mA MicroPowerTM LDO with PowerOK
SC70JW-8
0.50 BSC 0.50 BSC 0.50 BSC
AAT3237
1.75 0.10 0.225 0.075 2.00 0.20
2.20 0.20
0.048REF 0.15 0.05
0.85 0.15
1.10 MAX
0.100
7 3
0.45 0.10 2.10 0.30
4 4
0.05 0.05
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300mA MicroPowerTM LDO with PowerOK
AAT3237
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, and advise customers 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 subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 14
3237.2004.08.1.2

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