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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications General Description
The AAT3123/24 is a low noise, constant frequency charge pump DC/DC converter that uses a dual mode Load Switch (1X) and fractional (1.5X) conversion to maximize efficiency for White LED applications. The device can be used to produce current levels up to 20mA to drive up to 6 LEDs from a 2.7V to 5.5V input. Outputs may be operated individually or paralleled for driving higher-current LEDs. Low external parts counts (two 1F flying capacitors and two small 1F capacitors at VIN, and OUT) make the AAT3123/24 ideally suited for small battery-powered applications. AnalogicTechTM's Simple Serial ControlTM (S2CwireTM) interface is used to enable, disable and set the LED drive current with a 32 level logarithmic scale LED brightness control. The AAT3123/24 has a thermal management system to protect the device in the event of a short circuit condition at the output pin. Built-in soft-start circuitry prevents excessive inrush current during startup. A high charge pump switching frequency enables 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 AAT3123 is available in very small 12 pin TSOPJW package. The six output AAT3124 is available in a 16 pin 4x4mm QFN package.
AAT3123/4
Features
* * * * * * * * * * * * * * * *
ChargePumpTM
Dual Mode 1x and 1.5x Charge Pump for Maximum Efficiency Drives Low-VF & High-VF Type LEDs Up to 6 20mA Outputs 32 Position Logarithmic Scale with Digital Control Simple Serial ControlTM (S2CwireTM) interface Low Noise Constant Frequency Operation 1MHz Switching Frequency Small Application Circuit Regulated Output Current Automatic Soft-Start VIN Range: 2.7V to 5.5V No Inductors Iq < 1A in Shutdown Temperature Range -40 to 85C. 16 pin 4x4 QFN package (AAT3124) 12 pin TSOPJW-12 package (AAT3123)
Applications
* * * * White LED Backlighting White Photo-Flash for DSCs Color (RGB) Lighting Programmable Current Source
Typical Application
VIN C1+ C1 1F VBATTERY CIN 1F C OUT 1F VOUT C1C2+ C2 1F
AAT3124
C2D1 D2 D3 D4 D5 D6
EN/SET
EN/SET GND
D6
D5
D4
D3
D2
D1
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Pin Descriptions
Pin #
AAT3123 (TSOPJW-12) 8 7 6 5 AAT3124 (16LD 4x4 QFN) 16 1 4 5 2 3 6 7 10 11 12 9 14 15 8, 13
AAT3123/4
Symbol
Function
4 3 1 12 11 2 10 9
D1 D2 D3 D4 D5 D6 C1+ C1C2+ C2GND OUT IN EN/SET NC
Current source output #1 Current source output #2 Current source output #3 Current source output #4 Current source output #5 Current source output #6 Flying Capacitor 1 + terminal. Connect a 1F capacitor between C1+ and C1-. Flying Capacitor 1 - terminal Flying Capacitor 2 + terminal. Connect a 1F capacitor between C2+ and C2-. Flying Capacitor 2 - terminal Ground Charge pump output. Requires 1F capacitor connected between this pin and ground. Input power supply. Requires 1F capacitor connected between this pin and ground. Control Pin using S2Cwire serial interface. No Connection
Pin Configuration
12-Lead TSOPJW (Top View) 16 LD 4x4mm QFN (Top View)
EN/ D1 SET IN NC
C2+ OUT C1C1+ D4 D3
1 2 3 4 5 6 12 11
AAT 3123
10 9 8 7
C2GND IN EN/SET D1 D2
16
15
14
13 12 11 10 9
D2 D5* D6* D3
1 2 3 4 5 6 7 8
GND C2C2+ OUT
AAT 3124
D4 C1+ C1- NC
2
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Absolute Maximum Ratings1
Symbol
VIN VOUT FB,VEN/SET VEN/SET(MAX) IOUT 2 TJ
AAT3123/4
Description
Input Voltage Charge Pump Output FB or EN/SET to GND Voltage Maximum EN/SET to Input Voltage Maximum DC Output Current Operating Junction Temperature Range
Value
-0.3 to 6 -0.3 to 6 -0.3 to 6 0.3 150 -40 to 150
Units
V V V V mA 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
JA JA PD PD
Description
Thermal Resistance (QFN-16 package) Thermal Resistance 3 (TSOPJW-12 package) Maximum Power Dissipation (QFN-16 package, TA = 25C) 3, 4 Maximum Power Dissipation (TSOPJW-12 package, TA = 25C)
3
Value
50 160 2 0.625
Units
C/W W
3, 5
Note 3: Mounted on an FR4 board. Note 4: Derate 20mW/C above 25C. Note 5: Derate 6.25mW/C above 25C.
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Electrical Characteristics1
CIN = COUT = C1 = C2 = 1.0F; TA = -40 to 85C unless otherwise noted. Typical values are at TA = 25C, VIN = 3.5V. Symbol Description Conditions Min
2.7 3.0 VIN 5.5, Active, No Load Current EN=0 VIN = 3.5V, Code = 32, TA = 25C VD1:D4=3.6, VIN=3.5V VD5:VD6=3.6, VIN=3.5V VIN = 3.5V, IOUT(TOTAL) = 120mA, Measured from IN to OUT 1.8
AAT3123/4
Typ
Max
5.5 3.5 1 22
Units
V mA A mA % %
Input Power Supply VIN Operation Range Icc Operating Current ISHDN(MAX) IDX I(D-Match) CP Charge Pump TSS FCLK EN/SET VEN(L) VEN(H) TEN/SET LO TEN/SET HI TOFF Input Current Shutdown Current Output Current Current Matching between any two outputs Charge Pump Section Efficiency Section Soft start time Clock Frequency Enable Threshold Low Enable Threshold High EN/SET low time Minumum EN/SET high time EN/SET Off Timeout EN/SET input leakage
18
20 0.5 0.5 93
200 1000 VIN = 2.7 to 5.5V VIN = 2.7 to 5.5V 0.5 1.4 0.3 50 -1 500 1 75
s kHz V V s ns s A
Note 1: The AAT3123/4 is guaranteed to meet performance specification over the -40C to 85C operating temperature range and are assured by design, characterization and correlation with statistical process controls.
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Typical Characteristics
(Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1F, TA = 25C) Efficiency vs. VIN (4x20mA)
100% 95% 90% VDIODE = 3.2V VDIODE = 3.0V VDIODE = 3.4V 85% 80% 75% 70% 65% 60% 55% 50% 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
100% 95% 90%
AAT3123/4
Efficiency vs. VIN (4x10mA)
VDIODE = 3.2V VDIODE = 3.0V
VDIODE = 3.4V
Efficiency
Efficiency
85% 80% 75% 70% 65% 60% 55% 50% 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
VIN (V)
VIN (V)
IDIODE vs. VIN (4x20mA)
85 VDIODE = 3.2V 80 75 70 65 60 2.7
35 45
IDIODE vs. VIN (4x10mA)
VDIODE = 3.4V
IDIODE (mA)
IDIODE (mA)
VDIODE = 3.0V
VDIODE = 3.2V
40
VDIODE = 3.4V
VDIODE = 3.0V
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
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
VIN (V)
VIN (V)
Quiescent Current vs. VIN
2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 VDIODE = 3.0V 0.4 0.2 0.0 2.7 2.9 3.1 3.3 0.850 0.825 0.800 0.775 0.750 0.725 VDIODE = 3.4V VDIODE = 3.2V 0.700 0.675 0.650 0.625 0.600 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 2.5 3.0
VIH and VIL vs. VIN
Quiescent Current (mA)
3.5
4.0
4.5
5.0
5.5
VIN (V)
VIN (V)
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Typical Characteristics
(Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1F, TA = 25C) Turn-On to Full Scale Charge-Pump
ENSET (1V/div) OUT (2V/div) VDIODE (1V/div) IIN (200mA/div) 50s/div
AAT3123/4
Turn-On to Full Scale Load-Switch
ENSET (1V/div) OUT (2V/div) VDIODE (2V/div) IIN (100mA/div) 50s/div
Charge Pump to Load Switch (80mA)
VIN (10mV/div) OUT (2V/div) VDIODE (2V/div) IIN (100mA/div) 50s/div
Load Switch to Charge Pump (80mA)
VIN (20mV/div) OUT (1V/div) VDIODE (1V/div) IIN (200mV/div) 50s/div
Turn-Off
VIN ENSET (1V/div) 20mV/div
80mA Load Characteristics
VDIODE (2V/div) IIN (100mA/div)
OUT
VDIODE 200s/div 1s/div
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Functional Block Diagram
VIN
AAT3123/4
Soft Start Control 1MHz Oscillator Voltage Reference 1x/1.5x Charge Pump
C1+ C1C2+ C2OUT
Current Current Reference
D1
Quad Output DAC
D2 D3 D4
EN/SET
S2Cwire Interface
32 x 8 bit ROM
Dual Output DAC
D5* D6*
*AAT 3124 only
GND
Functional Description
The AAT3123/24 is a dual mode Load Switch (1X) and high efficiency (1.5X) fractional charge pump device intended for white LED back light applications. The fractional charge pump consists of a low dropout linear voltage regulator followed by a 1.5X charge pump with multiple current-source outputs. To maximize power conversion efficiency an internal feedback control sensing circuit monitors the voltage required on the constant current source outputs. This control circuit then sets the load switch and charge pump functions based upon the input voltage level versus the output voltage level needed. This function significantly enhances over all device efficiency when the input voltage level is greater then the voltage required at the constant current source outputs. For the AAT3123, the 1X Load Switch / 1.5X charge pump mode is decided on the voltage sensed on the output D1. The AAT3124 bases the 1X Load Switch/1.5X charge pump mode decision is based on the voltage levels sensed on either the output D1D4 output group or the D5-D6 output group, which ever is greater. Switchover between the 1.5X (charge-pump) operating mode and the 1X (load switch) mode occurs automatically (as a function of input and output voltages) and does not require user intervention to maintain maximum efficiency.
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The AAT3123/24 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 output capacitor (COUT). The LDO/1.5X charge pump output is converted into four (D1 to D4) or six (D1-D4 and D5-D6) constant current outputs to drive four or six individual LEDs with a maximum current of 20mA each. The current source output magnitude is controlled by the EN/SET serial data S2C interface. The interface records rising edges of the EN/SET pin, and decodes them into 32 individual current level settings each 1dB apart (see Current Level Settings below). Code 32 is full scale, and Code 1 is full scale attenuated by 31dB. The modulo 32 interface wraps states back to state 1 after the 32nd clock. With each EN/SET pulse, the output current increases by 1dB. To decrease the output current by 1dB, 31 EN/SET clock pulses are required. The counter can be clocked at speeds up to 1MHz, so intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to -31dB, the lowest setting equal to 525A. 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 after the EN/SET pin transitions to a logic low state. 7
High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Applications Information
Constant Current Output Level Settings
The constant current source output amplitude for output D1 to D6 are set via the serial interface according to a logarithmic scale where each code is 1dB greater than the previous code. In this manner, LED brightness appears linear with each increasing code count. Because the outputs D1 to D6 are true independent constant current sources, the voltage observed on any single given output will be determined by the actual forward voltage (VF) for the LED being driven.
AAT3123/4
Normalized Output Current Settings
1.0 0.9
Normalized I OUT (D1 to D6)
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Code
Since the output current of the AAT3123/24 is programmable through its simple single-wire 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." Furthermore, with its high speed serial interface (1MHz data rate), the output current of the AAT3123/24 can 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.
Constant Current Source Output Programming Levels (mA):
Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
IOUT (mA)
0.549 0.627 0.706 0.784 0.863 1.020 1.098 1.255 1.412 1.569 1.804 1.961 2.275 2.510 2.824 3.137
Code
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
IOUT (mA)
3.529 4.000 4.471 5.020 5.647 6.353 7.059 7.922 8.941 10.039 11.216 12.627 14.118 15.843 17.804 20.000
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
EN/SET Serial Interface
The current source output magnitude is controlled by the EN/SET pin, using AnalogicTech's Simple Serial Control (S2Cwire) interface. The interface records rising edges of the EN/SET pin, and decodes them into 32 individual current level settings each 1dB apart. Code 32 is full scale, and Code 1 is full scale attenuated by 31dB. The modulo 32 interface wraps states back to state 1 after the 32nd clock, so 1dB of attenuation is achieved by clocking the EN/SET pin 31 times. The counter can be clocked at speeds up to 1MHz, so intermediate states are not visible. The first rising edge of EN/SET enables the IC and initially sets the output LED current to -31dB, the lowest setting equal to 525A. 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 after the EN/SET pin transitions to a logic low state. 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. A constant current is sourced as long as EN/SET remains in a logic high state. The current source outputs are switched off after EN/SET has remained in a low state for at least the tOFF timeout period.
AAT3123/4
EN/SET Timing
tHI
tLO
tOFF
EN/SET Code
OFF
1
2
3
OFF
LED Selection
The AAT3123/24 is specifically intended for driving white LED's. However, the device design will allow the AAT3123/24 to drive most types of LED's with forward voltage specifications ranging from 2.0V to 4.3V. LED applications may include main and subLCD display backlighting, camera photo-flash applications, color (RGB) LED's, 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 output 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 LED's. The low-dropout
current-sources in the AAT3123/24 makes it capable of driving LED's with forward voltages as high as 4.3V at full current from an input supply as low as 3.0V. Outputs can be paralleled to drive high current LED's without complication.
Device Switching Noise Performance
The AAT3123/24 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 AAT3123/24 soft-start feature prevents noise transient effects associated with in-rush currents during the start up of the charge pump circuit.
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the following sections only account for the efficiency of the charge pump section itself. Due to the unique circuit architecture and design of the AAT3123/24, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Since the AAT3123/24 outputs are pure constant current sources and typically drive individual loads, it is difficult to measure the output voltage for a given output (D1 to D6) to derive an overall output power measurement. For any given application, white LED forward voltage levels can differ, yet the output drive current will be maintained as a constant. 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 AAT3123/24 efficiency may be quantified under very specific conditions and is dependant upon the input voltage versus the output voltage seen across the loads applied to outputs D1 through D4 or D6 for a given constant current setting. Depending upon the case of VIN being greater than the specific voltage seen across the load on D1 (or D5 when the AAT3124 is used) the device will operate in "Load Switch" mode. If the voltage seen on the constant current source output is less than VIN then the device will operate in 1.5X charge pump mode. Each of these two modes will yield different efficiency values. One should refer to the following two sections for explanations for each operational mode. load connected to the constant current source outputs. When in "Load Switch" mode, the voltage conversion efficiency is defined as output power divided by input power: = POUT/PIN The expression to define the ideal efficiency ( ) can be rewritten as: = POUT/PIN = (VOUT x IOUT)/(VIN x IOUT) = VOUT/VIN or (%) = 100(VOUT/VIN)
AAT3123/4
Charge Pump Section Efficiency
The AAT3123/24 contains a fractional charge pump which will boost the input supply voltage in the event where VIN is less then the voltage required on the constant current source outputs. The efficiency () can be simply defined as a linear voltage regulator with an effective output voltage that is equal to one and a half 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: = POUT/PIN = (VOUT x IOUT)/(VIN x 1.5IOUT) = VOUT/1.5VIN (%) = 100(VOUT/1.5VIN) For a charge pump with an output of 5 volts and a nominal input of 3.5 volts, the theoretical efficiency is 95%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 93%. These figures are in close agreement for output load conditions from 1mA to 100mA. Efficiency will decrease as load current drops below 0.05mA or when level of VIN approaches VOUT. Refer to the Typical Characteristics section for measured plots of efficiency versus input voltage and output load current for the given charge pump output voltage options.
Load Switch Mode Efficiency
The AAT3123/24 load switch mode is operational at all times and functions alone to enhance device power conversion efficiency when the condition exists where VIN is greater then voltage across the
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
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 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. 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.
AAT3123/4
Thermal Protection
The AAT3123/24 has a thermal protection circuit that will shut down the internal LDO and charge pump if the die temperature rises above the thermal limit as is the case during a short circuit of the OUT pin.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT3123/24. 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.
Driving Multiple LED's, White LED display module back lights and individual LED's connected in parallel
The AAT3123/24 D1 to D6 outputs are true constant current sources capable of driving up to 20mA each over the operation input voltage range. Since these outputs are true constant current sources, they may be connected in parallel to drive a single power output. Any combination of outputs (D1 to D6) may be connected in parallel. The maximum total output current is a sum of how many current sources are parallel connected. This feature is particularly useful to power pre-manufactured display modules which are pre-wired with white LED backlights connected in a parallel circuit configuration. Any combination of outputs may be connected in parallel to drive groups of LED's. The AAT3123 internal current source reference circuit bases feedback from current sensed on the D1 output. The AAT3124 internal current source reference circuit bases feedback from current sensed on the D1 and D5 outputs. For best operation, the only requirement for this type of application is the output D1 (and or D5 for the AAT3124) should always be connected to the load circuit. The AAT3124 may be used to drive multiple LED's having differing forward voltages. Using feedback techniques, the current in D1 to D4 output currents sources are referenced to the current in the LED connected to D1. In AAT3124 (six output version), the D5 and D6 output current sources are referenced to the current in D5, not to D1. If all six LED's are of similar type, the diodes will be matched in current, maintaining uniform LED brightness despite variations in manufacturer, production, etc. 11
Equivalent Series Resistance (ESR)
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 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. Large capacitor values are typically composed of X7R, X5R, Z5U or Y5V dielectric materials. Large ceramic capacitors, typically greater than 2.2 F are often available in low cost Y5V and Z5U dielectrics, but capacitors greater than 1F are typically not required for AAT3123/24 applications.
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
If however, the diodes are dramatically different in type comprising a mix of high-VF type and low-VFtype LED's, the AAT3124 has the capability to optimally drive up to four LED's of one-type and up to two LED's of another type simultaneously. Such a feature can be useful for driving different color LED's; driving both display backlight and photoflash LED's; or for driving main-LCD and sub-LCD display LED backlights from a single Charge Pump IC. For example, when driving independent RGB LED's, the green and blue type LED's typically require a high VF to operate (e.g. 3.7V) while the red LED needs a low forward voltage (e.g. 2V). By connecting the green and blue diodes to outputs D1 to D4 and the red diodes to D5 and D6, good control and uniformity in brightness is maintained despite the 2V difference in the diode forward voltages. The AAT3124 determines if the 1.5X charge pump circuit is needed based on the voltage on D1 and D5, which ever one is higher. If adequate voltage is available to drive the higher voltage LED (of output D1 or D5) without the charge pump running, the IC automatically switches into step down (1X) mode to maximize efficiency. Similarly, if a 4V photo-flash LED-array is connected to outputs D1 through D4 (with the outputs shorted together) and two 3.3V sub-LCD-display backlight LED's are connected to outputs D5 and D6, then the AAT3124 can optimally drive each set of LED's at the programmed current level (see application schematics). The photo-flash can be disabled by an N-channel switch connected in series with the photo-flash LED. The AAT3123/24 has only one programmed value of current and does not allow for separate on/off or brightness control of each current source output. This limitation can easily be circumvented by introducing grounded source N-channel MOSFET switches in series with the LEDs to turn any given LED (or bank of LEDs) on or off. The various LEDs can be turned on and off independently, simultaneously, or multiplexed to produce any variety of lighting effects. By reprogramming the current source (via the serial interface) between switching transitions, the brightness of individual LEDs, or banks of LEDs can also be controlled.
AAT3123/4
Charge Pump Compatibility
The 4-output AAT3123 is pin-compatible with the AAT3113 in both QFN and TSOPJW-12 packages. The six-output AAT3124 is pin compatible with the AAT3114 in the QFN package. Compared to the AAT3113/14, the AAT3123/24 offers an improved overall efficiency, wider operating range, and the ability to drive high-VF type LED's (up to 4.3V) at full current from a 3V input condition. The AAT3123/24 is well suited for battery powered applications using single-cell lithium-ion (Li-Ion) batteries (4.2V to 2.8V), lithium polymer batteries, and 3-series connected dry cells (3.6V).
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Additional Application Circuits
VIN C1+ C1 1F VBATTERY CIN 1F C OUT 1F VOUT C1C2+ C2 1F
AAT3123/4
AAT3123
C2D1 D2 D3 D4
EN/SET
EN/SET GND
D4
D3
D2
D1
Typical AAT3123 Application Circuit
VIN
C1+ C1 1F
VOUT VBATTERY CIN 1F C OUT 1F
C1C2+ C2 1F
AAT3123
C2D1 D2 D3 D4
Display Module D1 D2 D3 D4
EN/SET
EN/SET GND
RB
RB
RB
RB
Resistor R is optional
AAT3123 Driving a Display Module with 4 Paralleled White LED's
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High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Additional Application Circuits
VIN C1+ C1 1F VOUT VBATTERY CIN 1F C OUT 1F C1C2+ C2 1F
RB RB RB RB
AAT3123/4
D1
D2
D3
D4
AAT3124
C2D1 D2 D3 D4 D5 D6
Resistor R is optional
EN/SET
EN/SET GND
D5
D6
RB
RB
Resistor R is optional
AAT3124 Driving Two Groups of Paralleled White LED's (e.g. main-LCD & sub-LCD backlights)
VIN
C1+ C1 1F
VOUT VBATTERY CIN 1F C OUT 1F
C1C2+ C2 1F
AAT3124
C2D1 D2 D3 D4 D5 D6
EN/SET
EN/SET GND
D1
D2
D3
D4
D5
D6
RB*
RB*
RB*
RB*
RB*
RB*
Photo Flash LED
Resistor R is optional
*In some applications, white LED forward voltages (VF) can vary significantly. Ballast resistors between the LED cathodes and ground are recommended for balancing the forward voltage differences. The ballast resistor value may be approximated by the following equation: RB = VSOURCE - VF IF
AAT3124 Driving High Current Photo-Flash LED
14
3123.2003.09.1.1
High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Additional Application Circuits
VIN C1+ C1 1F VOUT VBATTERY CIN 1F COUT 1F C1C2+ C2 1F
AAT3123/4
AAT3124
C2D1 D2 D3 D4 D5 D6
EN/SET
EN/SET GND
D1
D2
D3
D4
D5
D6
Enable Display Backlight
Enable Keyboard Backlight
AAT3124 Driving Two Groups of Paralleled White LEDs (with Series N-channel Switch)
VIN
C1+ C1 1F
VOUT VBATTERY CIN 1F C OUT 1F
C1C2+ C2 1F
AAT3124
C2D1 D2 D3 D4 D5 D6
EN/SET
EN/SET GND
RED1
RED2
GRN1
GRN2
BLU1
BLU2
Enable Red Enable Green Enable Blue
AAT3124 Separately Driving RGB Color LEDs
3123.2003.09.1.1
15
High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Additional Application Circuits
VIN C1+ C1 1F VOUT VBATTERY CIN 1F COUT 1F C1C2+ C2 1F
AAT3123/4
AAT3124
C2D1 D2 D3 D4 D5 D6
EN/SET
EN/SET GND
Common-Anode RGB Color LED
RED
GRN
BLU
Enable Red Enable Green Enable Blue
AAT3124 Driving Common-Anode RGB Color LED
16
3123.2003.09.1.1
High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications Ordering Information
Package TSOPJW-12 QFN44-16 Marking1 IRXYY ISXYY Part Number (Tape and Reel) AAT3123ITP-20-T1 AAT3124ISN-20-T1
AAT3123/4
Note: Sample stock is generally held on all part numbers listed in BOLD. Note 1: XYY = assembly and date code.
Package Information
TSOPJW-12
0.10 0.20 + 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 + 0.10 1.00 - 0.065
0.04 REF
0.055 0.045
4 4
0.010
0.15 0.05
0.45 0.15
All dimensions in millimeters.
3123.2003.09.1.1
17
High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
QFN44-16
0.600 0.050
AAT3123/4
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.
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 18
3123.2003.09.1.1
0.900 0.050
0.450 0.050

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