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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications General Description
The AAT3143 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 AAT3143 can deliver current levels up to 80mA to drive white LEDs connected to the four current source outputs from a 2.7V to 5.5V input. The current source outputs may source up to 20mA each and 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 VIN and VOUT) makes the AAT3143 ideally suited for small battery-powered applications. Output current, and therefore brightness, is controlled via externally applied Pulse Width Modulation (PWM) control. Typically, PWM frequencies of up to 50kHz can be applied. The AAT3143 has a thermal management system to protect the device in the event of a short-circuit condition at the voltage output pin. Built-in soft-start circuitry prevents excessive inrush current during startup. A high charge pump switching frequency allows the use of very small external capacitors. A low current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1A. The AAT3143 is available in a Pb-free, space-saving, 2.85x3.0mm 12-pin TSOPJW package.
AAT3143
Features
* * * * * * * * * * *
ChargePumpTM
Input Voltage Range: 2.7V to 5.5V PWM Brightness Control Tri-Mode 1X, 1.5X, and 2X Charge Pump for Maximum Efficiency and VF Coverage Drives Four Low- or High-VF Type LEDs Up to 20mA LED Current per Channel No Inductors 1MHz Switching Frequency Small Application Circuit AutoBiasTM Technology IQ <1A in Shutdown 2.85x3.0mm TSOPJW-12 Package
Applications
* * * Programmable Current Sources White LED Backlighting White Photo Flash for Digital Still Cameras
Typical Application
2.7V to 5.5V
CIN 1F
IN
C1+ C1C2+
C1 1F C2 1F COUT 1F
AAT3143
PWM/EN EN/PWM
C2CP D1 D2 D3 D4
GND
D4
D3
D2
D1
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12
AAT3143
Symbol
C2+ CP C1C1+ D3 D2 D4 D1 EN/PWM IN GND C2-
Function
Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-. Charge pump output. Requires 1F capacitor connected between this pin and ground. Flying capacitor 1 negative terminal. Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-. Current source output #3. Current source output #2. Current source output #4. Current source output #1. Enable/PWM control pin. Input power supply. Requires 1F capacitor connected between this pin and ground. Ground. Flying capacitor 2 negative terminal.
Pin Configuration
TSOPJW-12 (Top View)
C2+ CP C1C1+ D3 D2
1 2 3 4 5 6
12 11 10 9 8 7
C2GND IN EN/PWM D1 D4
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Absolute Maximum Ratings1
Symbol
VIN VEN/PWM IOUT2 TJ TLEAD
AAT3143
Description
Input Voltage EN/PWM to GND Voltage 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 80 -40 to 150 300
Units
V V mA C C
Thermal Information3
Symbol
PD JA
Description
Maximum Power Dissipation Maximum Thermal Resistance
4
Value
0.625 160
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 6.25 mW/C above 25C. 3143.2006.05.1.0
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Electrical Characteristics1
CIN = CCP = C1 = C2 = 1.0F; TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C, VIN = 3.5V. Symbol Description Conditions Min
2.7 VD1:D4 = 2.0V, CP = 1X No Load Current, CP = 1.5X EN/PWM = 0 IOUT = 20mA, TA = 25C, VIN = 3.5V VD1:D4 = 3.6V, VIN = 3.5V VIN = 3.5V, IOUT(TOTAL) = 80mA, Measured from IN to CP 550 3 18 -3 20 0.5 93 1000 0.4 1.4 50 2
AAT3143
Typ
Max
5.5 5 1 22 3
Units
V A A mA % % kHz V V kHz s
Input Power Supply VIN Operation Range ICC ISHDN IDX I(D-Match) CP Charge Pump FCLK EN/PWM VEN(L) VEN(H) FPWM tON(MIN) Operating Current Shutdown Current Output Current Accuracy Current Matching2 Charge Pump Efficiency Section Clock Frequency Enable Threshold Low Enable Threshold High Maximum PWM Frequency Minimum Pulse Width
1. The AAT3143 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 I(D-Match) = (ID - IAVE)/IAVE.
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Typical Characteristics
VIN = 3.5V, CIN = CCP = C1 = C2 = 1F, TA = 25C, unless otherwise noted.
Efficiency
(100% Duty Cycle, 4x20mA/channel)
100 90
AAT3143
Turn-On to 1X Mode
(VIN = 4.2V)
Efficiency (%)
80 70 60 50 40 30 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
VEN (1V/div) VCP (2V/div) VLED (2V/div) IIN (100mA/div) Time (50s/div)
Input Voltage (V)
Turn-On to 1.5X Mode
(VIN = 3.5V)
Turn-On to 2X Mode
(VIN = 2.7V)
VEN (1V/div) VCP (2V/div) VLED (2V/div) IIN (50mA/div) Time (50s/div)
VEN (1V/div) VCP (2V/div) VLED (2V/div) IIN (50mA/div) Time (50s/div)
LED Turn-On Delay
(PWM Frequency = 500Hz)
LED Turn-On Delay
(PWM Frequency = 5kHz)
VEN (2V/div) VLED (2V/div)
VEN (2V/div) VLED (2V/div)
ILED (10mA/div)
ILED (10mA/div)
Time (5s/div)
Time (1s/div)
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Typical Characteristics
VIN = 3.5V, CIN = CCP = C1 = C2 = 1F, TA = 25C, unless otherwise noted.
1.5X Mode PWM Characteristic
(5kHz at 50% Duty Cycle)
20
AAT3143
PWM Duty Cycle vs. LED Current
LED Current (mA)
VEN (2V/div) ILED (20mA/div) IIN (100mA/div) VLED (2V/div) Time (50s/div)
18 16 14 12 10 8 6 4 2 0 0 10 20 30 40 50 60 70 80 90 100
100Hz 1kHz
10kHz
Duty Cycle (%)
Line Response
(1X Mode, 4x19mA Load)
Line Response
(1.5X Mode, 4x19mA Load) VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div)
VIN (0.5V/div) VLED (20mV/div) VCP (0.5V/div) ID (10mA/div) Time (1ms/div)
Time (1ms/div)
Load Characteristics
(1.5X Mode, 4x15mA Load)
90 80
Input Current vs. Input Voltage
(4x10mA)
Input Current (mA)
VF (20mV/div) IIN (10mA/div) VCP (20mV/div)
70 60 50 40 30 20 10 0 2.7 3.1 3.5
VDIODE = 3.4V
VDIODE = 3.0V
3.9 4.3 4.7 5.1 5.5
TIme (1s/div)
Input Voltage (V)
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Typical Characteristics
VIN = 3.5V, CIN = CCP = C1 = C2 = 1F, TA = 25C, unless otherwise noted.
AAT3143
VIH and VIL vs. VIN
0.850 0.825 0.800 0.775 0.750 0.725 0.700 0.675 0.650 0.625 0.600 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VIH VIL
Input Voltage (V)
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Functional Block Diagram
C1+ C1- C2+ C2-
AAT3143
IN
1X/1.5X/2X Charge Pump
CP
Soft-Start Control 1MHz Oscillator Voltage Reference D/A D/A D/A D/A
D1 D2 D3 D4
EN/PWM
EN/PWM
GND
Functional Description
The AAT3143 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 source output and sets the load switch and charge pump modes based on the input battery voltage and the current source output voltage. As the battery discharges over time, the AAT3143 charge pump is enabled when any of the four current source outputs nears 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 AAT3143 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 source outputs (D1 to D4) can drive four individual LEDs with a maximum current of 20mA each. The unused source outputs must be connected to GND, otherwise the part will operate only in 2X charge pump mode. The EN/PWM input allows the user to control the brightness of the four LEDs by PWMing up to 50kHz.
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Applications Information
EN/PWM Dimming Control
LED brightness is controlled with the EN/PWM pin. By driving the pin with a PWM signal, a corresponding pulse-width modulated current will be driven through the LEDs. In this way, the duty cycle sets the LED brightness level. The resulting average current that flows through the LED is calculated as follows:
AAT3143
Capacitor Selection
Careful selection of the four external capacitors CIN, C1, C2, and 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 only programmed for light current levels, then capacitor size may be decreased.
ILED = DC * 20mA
Capacitor Characteristics
The EN/PWM pin can be driven with a wide range of PWM frequencies. Because of the short turn-on delay during high frequency PWM, a frequency as high as 50kHz can be used. A low PWM frequency can also be used without complication. One should consider that below 50Hz, the human eye can begin to see LED flicker, so it is recommended that users choose an adequate PWM frequency exceeding 50Hz. Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3143. 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.
LED Selection
Although the AAT3143 is specifically intended for driving white LEDs, the device can also 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, 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 sources 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 sources in the AAT3143 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 highcurrent LEDs without complication.
Equivalent Series Resistance
ESR is an important characteristic to consider when selecting a capacitor. ESR is a 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.
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 AAT3143 applications.
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED 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.
AAT3143
Thermal Protection
The AAT3143 has a built-in thermal protection circuit that will shut down the charge pump if the die temperature rises above the thermal limit, as is the case during a short-circuit of the CP pin.
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High Efficiency 1X/1.5X/2X Charge Pump with PWM Control for White LED Applications Ordering Information
Package
TSOPJW-12
AAT3143
Marking1
ROXYY
Part Number (Tape and Reel)2
AAT3143ITP-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
TSOPJW-12
0.20 + 0.10 - 0.05
2.40 0.10
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
2.85 0.20
7 NOM 3.00 0.10
0.9625 0.0375
0.04 REF
0.15 0.05
+ 0.10 1.00 - 0.065
0.055 0.045
4 4
0.010
0.45 0.15 2.75 0.25
All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD.
(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
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