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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications General Description
The AAT3166 is a low noise, constant frequency charge pump DC/DC converter that uses a trimode load switch (1X), fractional (1.5X), and doubling (2X) conversion to maximize efficiency for white LED applications. The AAT3166 is capable of driving four LEDs for a total of 108mA from a 2.7V to 5.5V input. The current sinks may be operated individually or in parallel for driving higher-current LEDs. A low external parts count (two 1F flying capacitors and two small 1F capacitors at IN and OUTCP) make this part ideally suited for small, battery-powered applications. AnalogicTech's AS2CwireTM (Advanced Simple Serial ControlTM) serial digital input is used to enable, disable, and set current for each LED with a 16-level logarithmic scale plus four low-current settings down to 115A. For optimized efficiency, low-current settings require only 50A of housekeeping current. Each output of the AAT3166 is equipped with builtin protection for output short-circuit and auto-disable for load short-circuit condition. Built-in softstart circuitry prevents excessive inrush current during start-up. A low-current shutdown feature disconnects the load from the input and reduces quiescent current to less than 1A. The AAT3166 is available in a Pb-free, space saving, 3x3mm TDFN33-12 package and is rated over the -40C to +85C temperature range.
AAT3166
Features
* *
ChargePumpTM
* * * * * * * * * * *
VIN Range: 2.7V to 5.5V Fully Programmable Current with Single Wire -- 16-Step Logarithmic Scale -- 14/18/27mA Max Current -- Four Low-Current Settings Down to 115A -- Low IQ (50A) for Single-Channel, LowCurrent Mode Tri-Mode 1X, 1.5X, 2X Charge Pump for Maximum Efficiency and VF Coverage Drives Up to Four LEDs Individual Main-Sub (3-1) Group Control No Inductors, Low Noise Operation 1MHz Constant Switching Frequency Small Application Circuit Built-In Thermal Protection Built-In Auto-Disable for Open Circuit Automatic Soft Start IQ <1uA in Shutdown TDFN33-12 Package
Applications
* * * * * Color (RGB) Lighting Programmable Current Sink Transmissive LCD Display White LED Backlighting White Photo Flash for Digital Still Cameras
Typical Application
C1+
C1 1F
C2+
C2 1F
C12.7V to 5.5V
CIN 1F
C2OUTCP
IN
AAT3166
GND D1 D2
D1
D2
D3
D4
COUT 1F
EN/SET
EN/SET
D3 D4
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12 EP
AAT3166
Symbol
D4 EN/SET C1+ C1OUTCP C2+ C2IN GND D1 D2 D3
Function
Current sink input #4. AS2Cwire serial interface control pin. Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-. Flying capacitor 1 negative terminal. Charge pump output to drive load circuit. Requires 1F capacitor connected between this pin and ground. Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-. Flying capacitor 2 negative terminal. Input power supply. Requires 1F capacitor connected between this pin and ground. Ground. Current sink input #1. Current sink input #2. Current sink input #3. Exposed paddle; connect to ground as closely as possible to package.
Pin Configuration
TDFN33-12 (Top View)
D4 EN/SET C1+ C1OUTCP C2+
1 2 3 4 5 6
12 11 10 9 8 7
D3 D2 D1 GND IN C2-
2
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Absolute Maximum Ratings1
Symbol
VIN VEN/SET IOUT2 TJ TLEAD
AAT3166
Description
Input Voltage to GND EN/SET Voltage to GND Maximum DC Output Current Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6 -0.3 to VIN + 0.3 150 -40 to 150 300
Units
V V mA C C
Thermal Information3
Symbol
PD JA
Description
Maximum Power Dissipation4 Maximum Thermal Resistance
Value
2.0 50
Units
W C/W
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. Based on long-term current density limitation. 3. Mounted on an FR4 board. 4. Derate 20mW/C above 25C. 3166.2006.05.1.2
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Electrical Characteristics1
CIN = COUT = C1 = C2 = 1.0F; TA = -40C to +85C, unless otherwise noted. Typical values are at TA = 25C, VIN = 3.6V. Symbol Description Conditions Min
2.7 1X Mode, 3.0 VIN 5.5, Active, No Load Current, High Current Mode 1.5X Mode, 3.0 VIN 5.5, Active, No Load Current, High Current Mode 2X Mode, 3.0 VIN 5.5, Active, No Load Current, High Current Mode 1X Mode, 3.0 VIN 5.5, Active, No Load Current, Low Current Mode VEN/SET = 0V ISET = 18mA, TA = 25C ISET = 400A, TA = 25C VF:D1:D4 = 3.6V 0.3 1 1 50 -10 15 0.5 150 100 1000 0.4 1.4 0.3 50 75 500 500 1 75 1 10 1 A A % % % mV s kHz V V s ns s s s A mA
AAT3166
Typ
Max Units
5.5 V
Input Power Supply VIN Operation Range
ICC
Operating Current
Shutdown Current High Current Accuracy IDX Low Current Accuracy I(D-Match) Current Matching2 1X to 1.5X or 1.5X to 2X Transition VTH Threshold at Any ISINK Pin Charge Pump Section TSS Soft-Start Time FCLK Clock Frequency EN/SET VEN(L) Enable Threshold Low VIN = 2.7V VEN(H) Enable Threshold High VIN = 5.5V TEN/SET LO EN/SET Low Time TEN/SET_HI_MIN Minimum EN/SET High Time TEN/SET_HI_MAX Maximum EN/SET High Time TOFF EN/SET Off Timeout TLAT EN/SET Latch Timeout IEN/SET EN/SET Input Leakage
ISHDN
-1
1. The AAT3166 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. Current matching is defined as the deviation of any sink current from the average of all active channels.
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1F, TA = 25C.
Efficiency vs. Supply Voltage
100 90 80
AAT3166
Turn-On to 1X Mode
(VIN = 4.2V; 18mA Load)
18mA VF = 3.4V
Efficiency (%)
70 60 50 40 30 20 10 0 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5
EN (2V/div) VOUT (2V/div) VSINK (500mV/div) IIN (200mA/div) 100s/div
5.1mA VF = 3.0V 350A VF = 2.7V
Supply Voltage (V)
Turn-On to 1.5X Mode
(VIN = 3.5V; 18mA Load)
Turn-On to 2X Mode
(VIN = 2.8V; 18mA Load)
EN (2V/div) VOUT (2V/div) VSINK (500mV/div) IIN (200mA/div) 100s/div
EN (2V/div) VOUT (2V/div) VSINK (500mV/div) IIN (200mA/div) 100s/div
Turn-Off from 1.5X Mode
(VIN = 3.5V; 18mA Load)
19.0
Current Matching vs. Temperature
EN (2V/div)
Current (mA)
18.8 18.6 18.4 18.2 18.0 17.8 17.6 17.4 17.2 17.0 -40 -20 0 20 40 60 80
Channel 2 Channel 3 Channel 4
VF (1V/div)
IIN (100mA/div)
Channel 1
100s/div
Temperature (C)
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1F, TA = 25C.
Load Characteristics
(VIN = 3.8V; 1.5X Mode; 18mA Load)
AAT3166
Load Characteristics
(VIN = 2.8V; 2X Mode; 18mA Load)
VIN (40mV/div) VOUT (40mV/div) VSINK (40mV/div)
VIN (40mV/div) VOUT (40mV/div) VSINK (40mV/div)
500ns/div
500ns/div
Load Characteristics
(VIN = 4.1V; 1.5X Mode; 27mA Load)
Load Characteristics
(VIN = 3.2V; 2X Mode; 27mA Load)
VIN (40mV/div) VOUT (40mV/div)
VIN (40mV/div) VOUT (40mV/div) VSINK (40mV/div)
VSINK (40mV/div)
500ns/div
500ns/div
Input Ripple vs. Input Voltage
12
27mA 18mA
Input Ripple (mV)
10 8 6 4 2 0 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
14mA
Input Voltage (V)
6
3166.2006.05.1.2
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1F, TA = 25C.
AAT3166
EN/SET Latch Timeout vs. Input Voltage
EN/SET Latch Timeout (s)
350 400
EN/SET Off Timeout vs. Input Voltage
EN/SET Off Timeout (s)
300 250 200 150 100 50 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
350 300 250 200 150 100 50 0 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
-40C
-40C
25C
85C
25C
85C
Input Voltage (V)
Input Voltage (V)
Enable Threshold High vs. Input Voltage
Enable Threshold Low (V) Enable Threshold High (V)
1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
Enable Threshold Low vs. Input Voltage
-40C
-40C
25C
85C
25C
85C
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Input Voltage (V)
Input Voltage (V)
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Functional Block Diagram
C1+ C1- C2+ C2-
AAT3166
IN
1X, 1.5X, 2X Charge Pump
OUTCP
Soft-Start Control 1MHz Oscillator Voltage Reference D/A 6 x 16 Bit ROM D/A D/A
D1 D2 D3
EN/SET
AS2Cwire Interface
6 x 16 Bit ROM
D/A
D4
GND
Functional Description
The AAT3166 is a tri-mode load switch (1X) and high efficiency (1.5X or 2X) charge pump device intended for white LED backlight applications. To maximize power conversion efficiency, an internal sensing circuit monitors the voltage required on each constant current sink input and sets the load switch and charge pump modes based on the input battery voltage and the current sink input voltage. As the battery discharges over time, the AAT3166 charge pump is enabled when any of the four current sink inputs near dropout. The charge pump initially starts in 1.5X mode. If the charge pump output drops enough for any current source output to become close to dropout, the charge pump will automatically transition to 2X mode. The AAT3166 requires only four external components: two 1F ceramic capacitors for the charge pump flying
capacitors (C1 and C2), one 1F ceramic input capacitor (CIN), and one 0.33F to 1F ceramic charge pump output capacitor (COUT). The four constant current sink inputs (D1 to D4) can drive four individual LEDs with a maximum current of 27mA nominal each. Unused sink inputs should be connected to OUTCP, otherwise the part will operate only in 2X charge pump mode. The AS2Cwire serial interface enables the AAT3166 and sets the current sink magnitudes. AS2Cwire addressing allows independent control of two groups of current sink input: D1~D3 and D4.
Constant Current Output Level Settings
The constant current sink levels for D1 to D4 are set via the serial interface according to a logarithmic scale where each code is approximately 1.8dB lower than the previous code. In this manner, LED
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
brightness appears linear with each increasing code count. Because the inputs D1 to D4 are true independent constant current sinks, the voltage observed on any single given input will be determined by the actual forward voltage (VF) for the LED being driven. Since the input current sinks of the AAT3166 are programmable, no PWM (pulse width modulation) or additional control circuitry is needed to control LED brightness. This feature greatly reduces the burden on a microcontroller or system IC to manage LED or display brightness, allowing the user to "set it and forget it." With its high-speed serial interface (1MHz data rate), the input sink current of the AAT3166 can be changed successively to brighten or dim LEDs in smooth transitions (e.g., to fade-out) or in abrupt steps, giving the user complete programmability and real-time control of LED brightness. The 16 individual current level settings are each approximately 1.8dB apart (see Table 1). Code 1 is full scale; Code 15 is full scale attenuated by approximately 25dB; and Code 16 is reserved as a "no current" setting. Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
AAT3166
AS2Cwire Serial Interface
The current sink input magnitude of the AAT3166 is controlled by AnalogicTech's Advanced Simple Serial Control (AS2Cwire) serial digital input. AS2Cwire adds addressing capability for multiple data registers over the Simple Serial ControlTM (S2CwireTM), which is capable of controlling only a single register. The AAT3166 has four registers: Bank1, Bank2, Max Current, and Low Current. Three addresses are used to control the two registers. Address 0 addresses both registers simultaneously to allow the loading of both registers with the same data using a single write protocol. Address 1 addresses Register 1 for D1 to D3 current level settings. Address 2 addresses Register 2 for D4 current level settings. AS2Cwire relies on the number of rising edges of the EN/SET pin to address and load the registers. AS2Cwire latches data or address after the EN/SET pin has been held high for time TLAT. Address or data is differentiated by the number of EN/SET rising edges. Since the data registers are 4 bits each, the differentiating number of pulses is 24 or 16, so that Address 0 is signified by 17 rising edges, Address 1 by 18 rising edges, and Address 2 by 19 rising edges. Data is set to any number of rising edges between 1 and including 16. A typical write protocol is a burst of EN/SET rising edges signifying a particular address, followed by a pause with EN/SET held high for the TLAT timeout period, a burst of rising edges signifying data, and a TLAT timeout for the data registers. Once an address is set, then multiple writes consisting of data only (without address) to the corresponding data register are allowed. Address 0 is the default address on the first rising edge after the AAT3166 has been disabled. If data is presented on the first rising edge with no prior address, both data registers are simultaneously loaded. The maximum current level is determined by the value set in Register 3, the Max Current register. Three scales are available for high operating currents with maximum current levels of 27mA, 18mA, or 14mA. Each scale maintains approximately 1.8dB steps between settings. A separate mode is
27mA Max IOUT (mA)
27 22 18 14 12 10 8 6.2 5.2 4.3 3.3 2.9 2.4 1.9 1.4 0
18mA Max IOUT (mA)
18 15 12 10 7.9 6.3 5.1 4.1 3.5 2.9 2.2 1.9 1.6 1.3 1.0 0
14mA Max IOUT (mA)
14 11 8.8 7.1 6.0 4.8 3.8 3.1 2.6 2.1 1.7 1.4 1.2 1.0 0.7 0
Table 1: Current Level Settings.
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
available for ultra-low LED current operation. When the Max Current register (Register 3) is set to the Low Current setting, the Low Current register (Register 4) must be programmed. The two most significant bits of the Low Current register control whether or not a given bank of current sinks is enabled. The least two significant bits of the Low Current register set the current level for both banks. For low current settings, the charge pump may be enabled if required by the battery voltage and LED forward voltage conditions, and 1X mode quiescent current is approximately 100A for multiple channels or 50A for Channel 4 operation only. Both banks of current sinks must be in the same high or low current mode of operation. When EN/SET is held low for an amount of time greater than TOFF, the AAT3166 enters shutdown mode and draws less than 1A from VIN. Data and Address registers are reset to 0 during shutdown.
AAT3166
Low Current Register (Address 4)
Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Main Low Current On
No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes
Sub Low Current On
No No No No Yes Yes Yes Yes No No No No Yes Yes Yes Yes
Current
AS2Cwire Serial Interface Addressing
Address
0 1 2 3 4
115A 175A 280A 400A 115A 175A 280A 400A 115A 175A 280A 400A
EN/SET Rising Edges
17 18 19 20 21
Data Register AAT3166
1&2: D1~D4 Current 1: D1~D3 Current 2: D4 Current 3: Max Current 4: Low Current
Auto-Disable Feature
The AAT3166 is equipped with an auto-disable feature for each LED channel. After the IC is enabled and started up, a test current of 120A (typical) is forced through each sink channel. The channel will be disabled if the voltage of that particular SINK pin does not drop to a certain threshold. This feature is very convenient for disabling an unused channel or during an LED fail-short event.
Data
1 2 3 4
Max Current
18mA 27mA 14mA Low Current (see Low Current Register for values)
Thermal Protection
The AAT3166 has a built-in thermal protection circuit that will shut down the charge pump if the die temperature rises above the thermal limit, as would be the case during a short circuit of the OUTCP pin.
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
AS2Cwire Serial Interface Timing
Address
THI TLO TLAT TLAT
AAT3166
Data
EN/SET
1 2 17 18 1 2... n <= 16
Address
0
1
Data Reg 1
0
n-1
Data Reg 2
0
Applications Information
LED Selection
Although the AAT3166 is designed for driving white LEDs, the device also can be used to drive most types of LEDs with forward voltage specifications ranging from 2.0V to 4.7V. LED applications may include main and sub-LCD display backlighting, camera photo-flash applications, color (RGB) LEDs, infrared (IR) diodes for remotes, and other loads benefiting from a controlled output current generated from a varying input voltage. Since the D1 to D4 input current sinks are matched with negligible voltage dependence, the LED brightness will be matched regardless of the specific LED forward voltage (VF) levels. In some instances (e.g., in high-luminous-output applications such as photo flash), it may be necessary to drive high-VF type LEDs. The low-dropout current sinks in the AAT3166 make it capable of driving LEDs with forward voltages as high as 4.7V at full current from an input supply as low as 3.0V. Outputs can be paralleled to drive high-current LEDs without complication.
Device Switching Noise Performance
The AAT3166 operates at a fixed frequency of approximately 1MHz to control noise and limit harmonics that can interfere with the RF operation of cellular telephone handsets or other communication devices. Back-injected noise appearing on the input pin of the charge pump is 20mV peak-topeak, typically ten times less than inductor-based DC/DC boost converter white LED backlight solutions. The AAT3166 soft-start feature prevents noise transient effects associated with inrush currents during start-up of the charge pump circuit.
Capacitor Selection
Careful selection of the four external capacitors (CIN, C1, C2, COUT) is important because they will affect turn-on time, output ripple, and transient performance. Optimum performance will be obtained when low equivalent series resistance (ESR) ceramic capacitors are used; in general, low ESR may be defined as less than 100m. A value of 1F for all four capacitors is a good starting point when choosing capacitors. If the LED current sources are programmed only for light current levels, then the capacitor size may be decreased.
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3166. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is lowest cost, has a smaller PCB footprint, and is non-polarized. Low ESR ceramic capacitors help maximize charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage.
AAT3166
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1F 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 2.2F) are often available in lowcost Y5V and Z5U dielectrics, but capacitors greater than 1F are not typically required for AAT3166 applications. Capacitor area is another contributor to ESR. Capacitors that are physically large will have a lower ESR when compared to an equivalent material smaller capacitor. These larger devices can improve circuit transient response when compared to an equal value capacitor in a smaller package size.
Equivalent Series Resistance
ESR is an important characteristic to consider when selecting a capacitor. ESR is resistance internal to a capacitor that is caused by the leads, internal connections, size or area, material composition, and ambient temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors.
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications Ordering Information
Package
TDFN33-12
AAT3166
Marking1
PXXYY
Part Number (Tape and Reel)2
AAT3166IWP-T1
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
TDFN33-12
Index Area (D/2 x E/2)
Detail "B"
3.00 0.05
2.40 0.05
0.3 0.10 0.16 0.375 0.125 0.075 0.075 0.1 REF
Top View
Bottom View
Pin 1 Indicator (optional)
7.5 7.5
+ 0.05 0.8 -0.20
0.229 0.051
0.05 0.05
Option A: C0.30 (4x) max Chamfered corner
Option B: R0.30 (4x) max Round corner
Detail "B"
Side View
All dimensions in millimeters.
Detail "A"
1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3166.2006.05.1.2
0.23 0.05
0.45 0.05
Detail "A"
3.00 0.05
1.70 0.05
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High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
AAT3166
(c) 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 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. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 14
3166.2006.05.1.2

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