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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications General Description
The AAT3153 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 AAT3153 is capable of driving six LED channels 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 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 and sub-display group control. The AAT3153 consumes extremely low current internally (50A typical) at light load for optimized efficiency. Each output of the AAT3153 is equipped with builtin protection for VOUT short-circuit and auto-disable for load short-circuit conditions. 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 AAT3153 is available in a Pb-free, space-saving, thermally-enhanced 16-pin 4x4mm QFN 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 (50A) at Light Load Tri-Mode 1X, 1.5X, and 2X Charge Pump for Maximum Efficiency and VF Coverage Drives Up to Six LED Channels 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 Thermally-Enhanced 4x4mm 16-Pin QFN Package
Preliminary Information
Applications
* * * * Color (RGB) Lighting Programmable Current Sinks White LED Backlighting White Photo Flash for Digital Still Cameras
Typical Application
2.7V to 5.5V
CIN 1F
VIN
C1+
C1 1F
C1C2+
AAT3153
C2VOUT
C2 1F
D1
D2
D3
D4
D5
D6 COUT 1F
EN/SET
EN/SET
D1 D2 D3 D4 D5 GND D6
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9, 11 10 12 13 14 15 16 EP
Symbol
D6 EN/SET N/C VOUT C2+ C1+ C1C2GND IN D1 D2 D3 D4 D5
Function
Current sink input #6. S2Cwire serial interface control pin. No connection. 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 1 positive terminal. Connect a 1F capacitor between C1+ and C1-. Flying capacitor 1 negative terminal. Flying capacitor 2 negative terminal. Ground. Input power supply. Requires 1F capacitor connected between this pin and ground. Current sink input #1. Current sink input #2. Current sink input #3. Current sink input #4. Current sink input #5. Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
QFN44-16 (Top View) D2 D3
14 13
D5
16
D4
15
D6 EN/SET N/C VOUT
1
12
D1 GND IN GND
2
11
AAT3153
3 10 4 5 6 7 8 9
C1+ C2+
C2C1-
2
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Absolute Maximum Ratings1
Symbol
VIN VEN/SET IOUT2 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 + 0.3 180 -40 to 150 300
Units
V V mA C C
Thermal Information3
Symbol
PD JA
Description
Maximum Power Dissipation Maximum Thermal Resistance
4
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 6.25mW/C above 25C. 3153.2005.12.0.93
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AAT3153
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 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 = 30mA, TA = 25C 0.3 1 2.0 50 18 20 0.5 150 1 22
Typ
Max
5.5 1 3 3.7
Units
V
Input Power Supply VIN Operation Range
ICC
Operating Current
mA
Shutdown Current ISINK Average Current Accuracy Current Matching Between Any I(D-Match) VF:D1:D4 = 3.6V Two Current Sink Inputs2, 3 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 IDX
A A mA % mV
100 1000 0.4 1.4 0.3 50 75 500 500 1 75
s kHz V V s ns s s s A
-1
1. The AAT3153 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. 3. Specification applies only to the tri-mode charge pump.
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Typical Characteristics
Efficiency vs. Supply Voltage
100 90 10mA VF = 3.1V 20mA VF = 3.4V
Turn-On to 1X Mode
(VIN = 4.2V; 20mA Load)
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)
Time (100s/div)
Turn-On to 1.5X Mode
(VIN = 3.8V; 20mA Load)
Turn-On to 2X Mode
(VIN = 2.8V; 20mA Load)
EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div)
EN (2V/div) CP (2V/div) VSINK (500mV/div) IIN (200mA/div)
Time (100s/div)
Time (100s/div)
Turn-Off from 1.5X Mode
(VIN = 3.5V; 20mA Load)
20.2
Current Matching vs. Temperature
Channel 2 20.0 Channel 1
EN (2V/div) Current (mA) VF (1V/div) IIN (100mA/div)
19.8 19.6 Channel 3 19.4 19.2 -40 -20 0 20 40 60
Channel 5
Channel 4 Channel 6 80
Time (100s/div)
Temperature (C)
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Typical Characteristics
Load Characteristics
(VIN = 4.0V; 1.5X Mode; 20mA Load) VIN (40mV/div) CP (40mV/div) VIN (40mV/div) CP (40mV/div)
Load Characteristics
(VIN = 3.1V; 2X Mode; 20mA Load)
VSINK (40mV/div)
VSINK (40mV/div)
Time (500ns/div)
Time (500ns/div)
TLAT vs. VIN
350 300 250 400 350
TOFF vs. VIN
-40C TOFF (s)
300 250 200 150 100 50 0
-40C
TLAT (s)
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
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
VIN (V)
VIN (V)
Input Ripple vs. VIN
25 20 15 10 5 0 2.50 2.67 2.84 3.01 3.18 3.35 3.52 3.69 3.86 4.03 4.20
Amplitude (mV)
30mA
20mA 10mA
VIN (V)
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Typical Characteristics
VIH vs. VIN
1.2 1.1 1 0.9 1.2 1.1
VIL vs. VIN
-40C VIL (V)
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
-40C
VIH (V)
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
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
VIN (V)
VIN (V)
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AAT3153
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 D/A
D1 D2 D3 D4 D5 D6 D6
EN/SET
S2Cwire Interface
6 x 16 bit ROM
D/A D/A
Functional Description
The AAT3153 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 AAT3153
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 AAT3153 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).
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
The six constant current sink inputs (D1 to D6) can drive six 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 AAT3153 and sets the current sink magnitudes. S2Cwire addressing allows independent control of two groups of current sink input: D1-D4 and D5-D6. The S2Cwire serial interface has flexible timing. Data can be clocked-in at speeds greater than 1MHz, or much slower, such as 15kHz. After data is submitted, EN/SET is held high to latch the data. Once EN/SET has been held in the logic high state for time TLAT, the programmed current becomes active and the internal data register is reset to zero. For subsequent current level programming, the number of rising edges corresponding to the desired code must be entered on the EN/SET pin. When EN/SET is held low for an amount of time greater than TOFF, the AAT3153 enters into shutdown mode and draws less than 1A from VIN. The internal data register is reset to zero during shutdown. Main Group (D1-D4) IOUT (mA)
20 14 10 7 20 14 10 7 0 0 0 0 0.05 0.5 1 2
Constant Current Output Level Settings
The constant current sink levels for D1 to D6 are set via the serial interface. No PWM (pulse width modulation) or additional control circuitry are 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 AAT3153 can be changed successively to brighten or dim LEDs, giving the users real-time control of LED brightness. Because the inputs D1 to D6 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.
Data
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Sub Group (D5-D6) 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 AAT3153 is controlled by AnalogicTech's S2Cwire serial interface. The interface records rising edges of the EN/SET pin and decodes them into 16 different states, as indicated in Table 1. There are four brightness levels for the main or sub-display group with the possibility of individually turning ON or OFF each group. To further optimize power efficiency, the AAT3153 also offers four low-current levels for dim LED operation (Data 13 through 16). During this low-current mode, the internal supply current reduces to only 50A typical.
Table 1: AAT3153 Current Settings.
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AAT3153
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 AAT3153 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 SINK pin does not drop to certain threshold. This feature is very convenient for disabling an unused channel or during an LED fail short event.
tions such as photo flash), it may be necessary to drive high-VF type LEDs. The low-dropout current sinks in the AAT3153 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 AAT3153 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 AAT3153 soft-start feature prevents noise transient effects associated with inrush currents during start-up of the charge pump circuit.
Thermal Protection
The AAT3153 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.
Applications Information
LED Selection
Although the AAT3153 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 current generated from a varying input voltage. Since the D1 to D6 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 applica-
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the following sections only accounts for the efficiency of the charge pump section itself. Due to the unique circuit architecture and design of the AAT3153, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the AAT3153 inputs are pure constant current sinks and typically drive individual loads, it is difficult to measure the output voltage for a given input (D1 to D6) to derive an overall output power measurement. For any given application, white LED forward voltage levels can differ, yet the load drive current will be maintained as a constant.
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
This makes quantifying output power a difficult task when taken in the context of comparing to other white LED driver circuit topologies. A better way to quantify total device efficiency is to observe the total input power to the device for a given LED current drive level. The best white LED driver for a given application should be based on trade-offs of size, external component count, reliability, operating range, and total energy usage...not just % efficiency. The AAT3153 efficiency may be quantified under very specific conditions and is dependent upon the input voltage versus the output voltage seen across the loads applied to inputs D1 through D6 for a given constant current setting. Depending on the combination of VIN and voltages sensed at the current sinks, the device will operate in load switch mode. When any one of the voltages sensed at the current sinks nears dropout, the device will operate in 1.5X or 2X charge pump mode. Each of these modes will yield different efficiency values. Refer to the following two sections for explanations for each operational mode.
Charge Pump Section Efficiency
The AAT3153 contains a fractional charge pump that will boost the input supply voltage when VIN is less than the voltage required on the constant current sink inputs. The efficiency () can be simply defined as a linear voltage regulator with an effective output voltage that is equal to one and one half or two times the input voltage. Efficiency () for an ideal 1.5X charge pump can typically be expressed as the output power divided by the input power. POUT PIN
=
In addition, with an ideal 1.5X charge pump, the output current may be expressed as 2/3 of the input current. The expression to define the ideal efficiency () can be rewritten as: = -or VOUT 1.5VIN POUT VOUT x IOUT VOUT = = PIN VIN x 1.5IOUT 1.5VIN
Load Switch Mode Efficiency
The AAT3153 load switch mode is operational at all times and functions alone to enhance device power conversion efficiency when VIN is greater than the voltage across the load. When in load switch mode, the voltage conversion efficiency is defined as output power divided by input power: P = OUT PIN The expression to define the ideal efficiency () can be rewritten as: POUT VOUT x IOUT VOUT = = PIN VIN x IOUT VIN
(%) = 100
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 the capacitor size may be decreased.
= -or-
Capacitor Characteristics
(%) = 100 VOUT VIN Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3153. Ceramic capacitors offer many advantages over their tantalum and aluminum elec-
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
trolytic counterparts. A ceramic capacitor 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.
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 AAT3153 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 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.
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications Ordering Information
Package
QFN44-16
Marking1
Part Number (Tape and Reel)2
AAT3153ISN-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
QFN44-16
0.600 0.050
Pin 1 Dot By Marking
0.330 0.050
13 16
Pin 1 Identification
0.650 BSC
1
4.000 0.050
R0.030Max
9 4
8
5
4.000 0.050
2.280 REF
Top View
Bottom View
2.400 0.050
0.0125 0.0125
0.203 0.025
Side View
All dimensions in millimeters.
1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3153.2005.12.0.93
0.900 0.050
0.450 0.050
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AAT3153
High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications
(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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 14
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