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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications General Description
The AAT3152 is a low noise, constant frequency charge pump DC/DC converter that uses a tri-mode load switch (1X), fractional (1.5X), and doubling (2X) conversion to maximize efficiency for white LED applications. The AAT3152 is capable of driving four-channel LEDs from a 2.7V to 5.5V input. The current sinks may be operated individually or in parallel for driving higher-current LEDs. Low external parts count (two 1F flying capacitors and two small 1F capacitors at VIN and VOUT) makes this part ideally suited for small battery-powered applications. AnalogicTech's S2CwireTM (Simple Serial ControlTM) serial digital input is used to enable, disable, and set current for each LED with eight settings (20mA down to 50A) including main/sub-display group control. The AAT3152 consumes extremely low current internally (80A typical) at light load for optimized efficiency. Each output of the AAT3152 is equipped with builtin protection for VOUT short circuit and auto-disable for load short-circuit condition. Built-in soft-start circuitry prevents excessive inrush current during start-up. A low current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1A. The AAT3152 is available in a space-saving, thermal-enhanced 12-pin 3x3mm DFN package.
Features
* *
ChargePumpTM
* * * * * * * * * *
VIN Range: 2.7V to 5.5V Fully Programmable Current with Single Wire * Eight-Step Current: 20mA to 50A * Individual Main-Sub Group Control * Low IQ (80A) at Light Load Tri-Mode 1X, 1.5X, and 2X Charge Pump for Maximum Efficiency and VF Coverage Drives 1-4 Channels of LEDs No Inductors, Low Noise Operation 1MHz Constant Switching Frequency Small Application Circuit Built-In Thermal Protection Built-In Auto-Disable for Short-Circuit Automatic Soft-Start IQ <1A in Shutdown Thermal-Enhanced 3x3mm12-Pin DFN Package
Preliminary Information
Applications
* * * * Color (RGB) Lighting Programmable Current Sinks White LED Backlighting White Photo Flash for DSCs
Typical Application
2.7V to 5.5V
CIN 1F
VIN
C1+
C1 1F
C1C2+
AAT3152
C2VOUT
C2 1F
D1
D2
D3
D4
COUT 1F
EN/SET
EN/SET
D1 D2 D3 GND D4
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AAT3152
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
Symbol
D4 EN/SET C1+ C1OUTCP C2+ C2IN GND D1 D2 D3
Function
Current sink input #4. S2Cwire serial interface control pin. Flying capacitor 1 + terminal. Connect a 1F capacitor between C1+ and C1-. Flying capacitor 1 - terminal. Charge pump output to drive load circuit. Requires 1F capacitor connected between this pin and ground. Flying capacitor 2 + terminal. Connect a 1F capacitor between C2+ and C2-. Flying capacitor 2 - 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 (bottom); connect to GND directly beneath package.
Pin Configuration
DFN33-12 (TopView)
D4 EN/SET C1+ C1VOUT C2+
1 2 3 4 5 6
12 11 10 9 8 7
D3 D2 D1 GND VIN C2-
2
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Absolute Maximum Ratings1
Symbol
VIN VEN/SET IOUT 2 TJ TLEAD
Description
Input Voltage EN/SET 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 + 0.3 150 -40 to 150 300
Units
V V mA C C
Notes: 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.
Thermal Information
Symbol
PD JA
Description
Maximum Power Dissipation Maximum Thermal Resistance1
1, 2
Value
2.0 50
Units
W C/W
Notes: 1. Mounted on an FR4 board. 2. Derate 20mW/C above 25C.
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Electrical Characteristics1
CIN = COUT = C1 = C2 = 1.0F; TA = -40C - 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 1.5X Mode, 3.0 VIN 5.5, Active, No Load Current 2X Mode, 3.0 VIN 5.5, Active, No Load Current 50A Setting, 1X Mode EN/SET = 0 ISET = 20mA, TA = 25C VF:D1:D4 = 3.6V 0.3 1 1.5 80 -10 150 1 10 12
Typ
Max
5.5 1 3 3
Units
V
Input Power Supply VIN Operation Range
mA
ICC
Operating Current
Shutdown Current ISINK Average Current Accuracy I(D-Match) Current Matching (Note 2) VTH 1X to 1.5X or 1.5X to 2X Transition Threshold at Any Current Sink Pin Charge Pump Section TSS Soft-Start Time FCLK Clock Frequency EN/SET VEN(L) Enable Threshold Low VEN(H) Enable Threshold High TEN/SET LO EN/SET Low Time TEN/SET HI Minimum EN/SET High Time TOFF EN/SET Off Timeout TLAT EN/SET Latch Timeout EN/SET Input Leakage IEN/SET
ISHDN IDX
A A % % mV
100 1000 0.4 VEN/SET VEN/SET VEN/SET VEN/SET <0.6V >1.4V <0.6V >1.4V 1.4 0.3 50 500 500 1 75
s kHz V V s ns s s A
-1
Notes: 1. The AAT3152 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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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Typical Characteristics
Efficiency vs. Supply Voltage
100
Turn On to 1X Mode
(VIN = 4.2V; 20mA Load)
10mA
90
20mA
Efficiency (%)
EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div)
80
70
60
50 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2
Supply Voltage (V)
200s/div
Turn On to 1.5X Mode
(VIN = 3.5V; 20mA Load)
Turn On to 2X Mode
(VIN = 2.8V; 20mA Load)
EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) 200s/div
EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div) 200s/div
Turn Off from 1.5X Mode
(VIN = 3.5V; 20mA Load) EN (2V/div) VF (1V/div) IIN (100mA/div)
200s/div
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Functional Block Diagram
C1+
C1- C2+
C2-
VIN
1X, 1.5X and 2X Charge Pump
VOUT
Soft-Start Control 1MHz Oscillator Voltage Reference D/A 6 x 16 bit ROM D/A D/A
D1 D2 D3
EN/SET
S2C Interface
6 x 16 bit ROM
D/A
D4 GND
Functional Description
The AAT3152 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 AAT3152 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 AAT3152 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 20mA each. The unused sink inputs must be connected to VOUT, otherwise the part will operate only in 2X charge pump mode. The S2Cwire serial interface enables the AAT3152 and sets the current sink magnitudes. S2Cwire addressing allows independent control of two groups of current sink input: D1-D3 and D4.
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
Constant Current Output Level Settings
The constant current sink levels for D1 to D4 are set via the serial interface. 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 (up to 1MHz data rate), the input sink current of the AAT3152 can be changed successively to brighten or dim LEDs, giving the users real-time control of LED brightness. 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.
AAT3152 Current Setting
Data Main Group (D1-D3) IOUT (mA)
20 14 10 7 20 14 10 7 0 0 0 0 0.05 0.5 1 2
Sub Group (D4) IOUT (mA)
20 14 10 7 0 0 0 0 20 14 10 7 0.05 0.5 1 2
S2Cwire Serial Interface
The current sink input magnitude on the AAT3152 is controlled by AnalogicTech's S2Cwire serial digital input. It relies on the number of rising edges of the EN/SET pin to address and load the registers. S2Cwire latches data or address after the EN/SET pin has been held high for time TLAT. The interface records rising edges of the EN/SET pin and decodes them into 16 different states, as indicated in the Current Setting table. There are four brightness levels for main or sub-display group with the possibility of individually turning ON or OFF each group. To further optimize power efficiency, the AAT3152 also offers four low-current levels for dim LED operation (data 13-16). During this low current mode, the internal supply current reduces to only 80A typical. The counter can be clocked at speeds up to 1MHz, such that intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to 20mA. Once the final clock cycle is input for the desired brightness level, the EN/SET pin is held high to maintain the device output current at the programmed level. The device is disabled 500s (TOFF) after the EN/SET pin transitions to a logic low state.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
The EN/SET timing is designed to accommodate a wide range of data rates. After the first rising edge of EN/SET, the charge pump is enabled and reaches full capacity after the soft-start time (TSS). During the soft-start time, multiple clock pulses may be entered on the EN/SET pin to set the final output current level with a single burst of clocks. Alternatively, the EN/SET clock pulses may be entered one at a time to gradually increase the LED brightness over any desired time period. The current outputs remain constant as long as EN/SET remains in a logic high state. The current outputs are switched off after EN/SET has remained in a low state for at least the TOFF timeout period; then, the AAT3152 enters shutdown mode and draws less than 1A from VIN. Data are reset to 0 during shutdown.
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
S2Cwire Serial Interface Timing
T HI T LO TLAT TOFF
EN/SET
1 2 n n <= 16
Data Reg
1
n
0
Auto-Disable Feature
The AAT3152 is equipped with an "auto-disable" feature for each LED channel. After the IC is enabled and started up, a test current of 150A (typical) is forced through each sink channel. The channel will be disabled if the voltage of that particular current sink pin does not drop to a certain threshold. This feature is very convenient for disabling an unused channel (by tying the DX pin to VOUT) or during an LED fail short event.
Thermal Protection
The AAT3152 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 VOUT pin.
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 AAT3152 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 AAT3152 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 AAT3152 soft-start feature prevents noise transient effects associated with in-rush currents during start up of the charge pump circuit.
Applications Information
LED Selection
Although the AAT3152 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, color (RGB) LEDs, infrared (IR) diodes for remotes, and other loads benefiting from a controlled output
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
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
performance. Optimum performance will be obtained when low Equivalent Series Resistance (ESR) (<100m) ceramic capacitors are used. In general, low ESR may be defined as less than 100m. A capacitor 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 the capacitor size may be decreased. 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 COG materials. NPO and COG materials typically have tight tolerance and are stable over temperature. Larger capacitor values are typically composed of X7R, X5R, Z5U, or Y5V dielectric materials. Large ceramic capacitors, typically greater than 2.2F, are often available in lowcost Y5V and Z5U dielectrics, but capacitors greater than 1F are typically not required for AAT3152 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.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3152. 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 to maximize charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage.
Equivalent Series Resistance
ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor, which is caused by the leads, internal connections, size or area, material composition,
Thermal Protection
The AAT3152 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 VOUT pin.
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AAT3152
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Ordering Information
Package DFN33-12 Marking1 NQXYY Part Number (Tape and Reel) AAT3152IWP-T1
Note 1: XYY = assembly and date code.
Package Information
Index Area (D/2 x E/2) Detail "B"
3.00 0.05
Pin 1 Indicator (optional) 0.16 0.375 0.125 0.075 0.075 0.1 REF
Detail "A"
Bottom View Top View
7.5 7.5
+ 0.05 0.8 -0.20
0.229 0.051
Detail "B"
Option A: C0.30 (4x) max Chamfered corner Option B: R0.30 (4x) max Round corner
0.05 0.05
Side View
Detail "A"
All dimensions in millimeters.
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 10
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0.23 0.05
0.45 0.05
3.00 0.05

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