AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3103.2008.03.1.0 1
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General Description
The AAT3103 is a constant frequency charge-pump based
current-source white LED driver capable of driving one to
three LEDs up to 30mA, each. The charge pumps auto-
matically switch between 1x mode and 2x mode to main-
tain the highest efficiency and optimal LED current accu-
racy and matching. A low external parts count (one 1F
flying capacitor, two small 1F capacitors at IN and OUT
and one current setting resistor) makes the AAT3103 ide-
ally suited for small battery-powered applications.
The AAT3103-1/-2 uses AnalogicTech's Simple Serial
Control™ (S2Cwire™) interface to enable, disable, and
program the LED driving current. The AAT3103-4 employs
a Pulse Width Modulation (PWM) signal with up to 50kHz
frequency, 10% to 100% duty cycle to program the LED
current. A low-current shutdown feature disconnects the
load from IN and reduces quiescent current to less than
1A. Built-in soft-start circuitry prevents excessive inrush
current during start-up. Integrated short circuit and ther-
mal protection circuitry protects the device from damage.
The AAT3103 is available in a 2x2.1mm thermally
enhanced Pb-free 10-lead SC70JW-10 package.
Features
•
Source WLED Driver, up to 3 LEDs at up to 30mA, each
• Automatic Switching Between 1x and 2x Modes
• 900KHz Switching Frequency
• Linear LED Output Current Control
Single-wire, S2Cwire Interface
AAT3103-1: 16-step
AAT3103-2: 8-step
ON/OFF or PWM Interface
AAT3103-4
• ±10% LED Output Current Accuracy
• ±3% LED Output Current Matching
• Low-current Shutdown Mode
• Built-in Short Circuit and Thermal Protection
• Automatic Soft-start
• 2x2.1mm SC70JW-10 Package
Applications
• Cordless Phone Handsets
• Mobile Phone Handsets
• MP3 and PMP Players
• Digital Cameras
Typical Application
Input Voltage
2.7V to 5.5V
EN/SET
S2Cwire
Interface
IN
C+
C-
EN/SET
OUT
D1
D2
D3
RSET
RSET
14.3kΩ
COUT
1μF
AGND
WLEDs
OSRAM LW M 678
or equivalent
AAT3103-1
CP
1μF
CIN
1μF
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Pin Descriptions
Pin # Symbol Description
1 D1 LED1 Current Source Output. Connect LED1’s anode to D1 and its cathode to AGND.
2 OUT Charge Pump Output. Bypass OUT to AGND with a 1F or larger ceramic capacitor.
3 C- Charge Pump Capacitor Negative Node.
4 C+ Charge Pump Capacitor Positive Node. Connect a 1F ceramic capacitor between C+ and C-.
5IN
Power source input. Connect IN to the power source, typically the battery. Bypass IN to AGND with a
1F or larger ceramic capacitor.
6
EN/SET
(AAT3103-1/-2)
LED Enable and serial control input. EN/SET is the ON/OFF control for the LED and the S2Cwire digital
input for the AAT3103-1/-2 to control the LED brightness up to the maximum current set by RSET
.
EN/PWM
(AAT3103-4)
LED ON/OFF and PWM (Pulse Width Modulation) control input. This logic input controls the LED
outputs for the AAT3103-4. A PWM signal, ranging from 10% to 100% duty cycle, controls the LED
current linearly between minimum and the full-scale output set by RSET
.
7 RSET
A 1% tolerance resistor from this pin to AGND sets the maximum LED current value. For optimal LED
output current accuracy and matching in the AAT3103-1/-2/-4, a 14.3k resistor sets each full-scale
output current to 20mA.
8 AGND Analog Ground. Connect this pin to the system’s analog ground plane.
9 D3 LED3 Current Source Output. Connect LED3’s anode to D3 and its cathode to AGND.
10 D2 LED2 Current Source Output. Connect LED2’s anode to D2 and its cathode to AGND.
Pin Configuration
SC70JW-10
(Top View)
56
OUT
C-
C+
D2
D3
AGND
RSET
IN EN/SET (EN/PWM)
D1 1
2
3
47
8
9
10
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Absolute Maximum Ratings1
Symbol Description Value Units
IN, C+, C-, OUT, D1, D2, D3, and RSET Pin Voltages to AGND -0.3 to 6.0 V
EN/SET or EN/PWM Pin Voltage to AGND -0.3 to VIN + 0.3 V
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C
Thermal Information
Symbol Description Value Units
PDMaximum Power Dissipation2, 3 625 mW
ΘJA Maximum Thermal Resistance2160 °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. Mounted on an FR4 circuit board.
3. Derate 6.25mW/°C above 40 °C ambient temperature.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Electrical Characteristics1
IN = EN = 3.6V; CIN = 1F; COUT = 1F; CCP = 1F; RSET = 14.3k; TA=-40°C to 85°C unless otherwise noted. Typical
values are at TA = 25°C.
Symbol Description Conditions Min Typ Max Units
Input Power Supply
IN Input Voltage Range 2.7 5.5 V
IIN Input Operating Current
IN = 5.5V; EN = IN; VD1 = VD2 = VD3 = 0V 7.4 10
mA
IN = 5.5V; EN = IN; ID1 = ID2 = ID3 = FS,
excluding ID1-ID3; VD1 = VD2 = VD3 = IN – 1.5V 1.9 3
Operating, ID1 = ID2 = ID3 = OPEN 4 6.8
IIN(SHDN) Input Shutdown Current EN/SET or EN/PWM = GND 1 A
Charge Pump Section
IOUT OUT Maximum Output Current 100 mA
fOSC Charge Pump Oscillator Frequency 0.65 0.9 1.4 MHz
VIN_(TH) Charge Pump Mode Hysteresis ID1 = ID2 = ID3 = 20mA 325 mV
tOUT LED Output Current Start-up Time EN/SET or EN/PWM = IN 150 s
AAT3103-1/-2/-4: LED Current Source Outputs
ID_(MAX) D1 - D3 Current Accuracy DATA = 1; VIN – VF = 1.5V. 18 20 22 mA
ID_(MAX) D1 - D3 Current Matching DATA = 1; VIN – VF = 1.5V ±3 %
ID_(DATA15)
D1 - D3 Current Accuracy
(AAT3103-1 only) DATA = 15; VIN – VF = 1.5V 1.0 1.34 1.61 mA
ID_(DATA8)
D1 - D3 Current Accuracy
(AAT3103-2 only) DATA = 8; VIN – VF = 1.5V 1.0 1.34 1.61 mA
ID_(10%)
D1 - D3 Current Accuracy
(AAT3103-4 only) DC = 10%; VIN – VF = 1.5V 2.5 mA
VD_(TH)
D1- D3 Charge Pump Mode
Transition Threshold ID1 = ID2 = ID3 = 20mA 280 mV
VSET RSET Pin Voltage 1.14 1.18 1.22 V
AAT3103-1/-2: EN/SET and S2Cwire Control
VENH EN/SET Input High Threshold Voltage 1.4 V
VENL EN/SET Input Low Threshold Voltage 0.4 V
IEN(LKG) EN/SET Input Leakage Current EN/SET = IN = 5V -1 1 A
tEN/SET(OFF) EN/SET Input OFF Timeout 500 s
tEN/SET(LAT) EN/SET Input Latch Timeout 500 s
tEN/SET(LOW) EN/SET Input Low Time 0.3 75 s
tENSET(H-MIN) EN/SET Minimum High Time 50 ns
tENSET(H-MAX) EN/SET Maximum High Time 75 s
AAT3103-4: EN/PWM Current Control
VENH EN/PWM Input High Threshold Voltage 1.4 V
VENL EN/PWM Input Low Threshold Voltage 0.4 V
IEN(LKG) EN/PWM Input Leakage Current EN/PWM = IN = 5V -1 1 A
tPWM(ON) PWM Control Turn-on Delay 110 s
tEN/PWM EN/PWM Input OFF Timeout 0.15 1 ms
fPWM PWM Control Frequency Duty cycle = 80% 50 kHz
1. The AAT3103 is guaranteed to meet performance specifications over the -40°C to 85°C operating temperature range and is assured by design, characterization and correlation
with statistical process controls.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Typical Characteristics
Shutdown Current vs. Temperature
Temperature (°C)
ISHDN (µA)
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
-40 -15 10 35 60 85
VIN = 5.5V
VIN = 2.7V
Operating Current vs. Input Voltage
(VD1 = VD2 = VD3 = 0V)
Input Voltage (V)
IQ (mA)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
2.5 3 3.5 4 4.5 5 5.
5
-40°C
25°C
85°C
Operating Current vs. Input Voltage
(No Load; D1, D2, D3 Open)
Input Voltage (V)
IQ (mA)
3.6
3.8
3.9
4.1
4.2
2.5 3 3.5 4 4.5 5 5.5
85°C
25°C
-40°C
LED Current Matching vs. Temperature
Temperature (°C)
Current (mA)
19.0
19.5
20.0
20.5
21.0
-40 -15 10 35 60 85
D1
D2
D3
Efficiency vs. Input Voltage
Input Voltage (V)
Efficiency (%)
0
10
20
30
40
50
60
70
80
90
100
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
ILED = 30mA,VF = 3.5V
ILED = 20mA,VF = 3.2V
ILED = 10mA,VF = 3.0V
ILED Full Scale vs. RSET
RSET (kΩ)
ILED (mA)
0
7
14
21
28
35
8 1318 232833
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Typical Characteristics
EN Input High Threshold Voltage
vs. Input Voltage
Input Voltage (V)
VENH (V)
0.2
0.4
0.6
0.8
1.0
1.2
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
-40°C
25°C
85°C
EN Input Low Threshold Voltage
vs. Input Voltage
Input Voltage (V)
VENL (V)
0.2
0.4
0.6
0.8
1.0
1.2
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
-40°C
25°C
85°C
EN/SET Input Latch Timeout
vs. Input Voltage
Input Voltage (V)
tEN/SET(LAT) (V)
100
150
200
250
300
350
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
85°C
25°C
-40°C
EN/SET Input Off Timeout
vs. Input Voltage
Input Voltage (V)
tEN/SET(OFF) (V)
100
150
200
250
300
350
400
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
85°C
25°C
-40°C
Turn-On to 2X Mode
(VIN = 3.6V; 20mA/Dx)
Time (200µs/div)
EN/SET
(2V/div)
VOUT
(5V/div)
IIN
(200mA/div)
VD1
(2V/div)
4.2V
2.7V
3.2V
0A
0V
Turn-Off from 2X Mode
(VIN = 3.6V; 20mA/Dx)
Time (100µs/div)
EN/SET
(2V/div)
IIN
(200mA/div)
VD1
(2V/div)
0V
0V
0A
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Typical Characteristics
Turn-On to 1X Mode
(VIN = 4.2V; 20mA/Dx)
Time (200µs/div)
EN/SET
(2V/div)
VOUT
(2V/div)
IIN
(200mA/div)
VD1
(2V/div)
0V
0V
0A
0V
Output Ripple Waveform
(2X Mode; 20mA/Dx)
Time (1µs/div)
VOUT (AC)
(20mV/div)
VD1
(20mV/div)
VIN
(20mV/div)
0V
0V
0V
LED Current Transition
(VIN = 4.2V; 1.3mA to 20mA)
Time (100µs/div)
EN/SET
(2V/div)
VOUT
(2V/div)
IIN
(50mA/div)
VD1
(2V/div)
4.2V
2.7V
3.2V
0A
0V
LED Current Transition
(VIN = 4.2V; 20mA to 1.3mA)
Time (100µs/div)
EN/SET
(2V/div)
VOUT
(2V/div)
IIN
(50mA/div)
VD1
(2V/div)
4.2V
0V
0A
3.2V 2.7V
Input Current vs. Input Voltage
Input Voltage (V)
Input Current (mA)
0
50
100
150
200
250
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
ILED = 30mA
ILED = 20mA
ILED = 10mA
VIN Rising
VIN Falling
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3-Channel Charge-Pump LED DriverChargePumpTM
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3-Channel Charge-Pump LED DriverChargePumpTM
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Functional Description
The AAT3103 is a low-cost charge-pump solution designed
to drive up to three WLEDs. The charge pump operates
from a 2.7V to 5.5V power source and converts it to volt-
age levels necessary to drive the LEDs. LED current is
individually controlled through integrated current sourc-
es powered from the output of the charge pump. Low 1x
charge-pump output resistance and low-drop voltage
current sources allow the charge pump to stay in 1x
mode with an input voltage as low as 3.75V and LED
forward voltages as high as 3.2V with 20mA LED current.
Once in 2x mode, the charge pump monitors the input
supply voltage and automatically switches back to 1x
mode when there is sufficient input voltage.
The AAT3103 requires only four external components:
one 1F ceramic capacitor for the charge pump flying
capacitors (CP), one 1F ceramic input capacitor (CIN),
one 1F ceramic output capacitor (COUT) and a resistor
(RSET) to set the maximum LED current. The three con-
stant current outputs of the AAT3103 (D1 to D3) can
drive three individual LEDs with a maximum current of
30mA each. AnalogicTech’s S2Cwire serial interface
enables the AAT3103-1/-2 and changes the current
source magnitudes through the EN/SET pin. The
AAT3103-4 uses an external PWM signal to enable the IC
and control the brightness of the LEDs.
Constant Current Control Using RSET
The maximum current is programmed by an external
resistor at the RSET pin. With a 14.3k external resistor
at the RSET pin, the AAT3103 includes an integrated
serial LED current control that sets the full-scale LED
current between 20mA and 0.67mA. The full-scale LED
current can be set higher or lower than 20mA; see Table
4. For maximum accuracy, a 1% tolerance resistor is
recommended.
Functional Block Diagram
C–C+ OUT
AGND
IN
D3
D2
D1
S2Cwire Control
(PWM Control) DAC
EN/SET
(EN/ PWM) RSET
Two-Mode
CP Control
VF Monitoring 3
IREF
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
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Part Number Descriptions
Part Number Interface
Current Control,
Inverting
AAT3103IJQ-1 S2Cwire 16-step
AAT3103IJQ-2 S2Cwire 8-step
AAT3103IJQ-4 PWM Linear
S2Cwire Serial Interface
(AAT3103-1/-2 only)
The LED output current of the AAT3103-1/-2 is controlled
by AnalogicTech’s S2Cwire serial interface. Since the LED
current is programmable, no PWM or additional control
circuitry is needed to control the LED brightness. This
feature greatly reduces the burden on a microcontroller
or system IC to manage LED or display brightness, allow-
ing the user to “set it and forget it.” With its high-speed
serial interface (1MHz data rate), the LED current can be
changed quickly and easily. Also the non-pulsating LED
current reduces system noise and improves LED reliabil-
ity. The S2Cwire interface relies on the number of rising
edges to the EN/SET pin to set the register. A typical
write protocol is a burst of EN/SET rising edges, followed
by a pause with EN/SET held high for at least tLAT (500s).
The programmed current is then seen at the current
source outputs. When EN/SET is held low for an amount
of time longer than tOFF (500s), the AAT3103 enters into
shutdown mode and draws less than 1A from the input
and the internal data register is reset to zero.
The AAT3103-1/-2’s serial interface reduces the LED cur-
rent on each rising pulse of the enable input. If the
AAT3103 is in shutdown, the first rising edge of the EN/
SET input turns on the LED driver to the maximum cur-
rent. Successive rising edges decrease the LED current as
shown in Table 1 and Figure 2 for the AAT3103-1. For the
AAT3103-2, Table 2 and Figure 3 illustrate an 8-step LED
current control profile. .
1
EN/SET
2 n-1 n ≤ 16
Data Reg 0 n-1 0
THI
TLO TLAT TOFF
Figure 1: S2Cwire Serial Interface Timing.
S2C Data EN Rising Edges D1-D3 Current (mA)
1 1 20.1
2 2 18.8
3 3 17.5
4 4 16.1
5 5 14.8
6 6 13.4
7 7 12.1
8 8 10.7
9 9 9.4
10 10 8.1
11 11 6.7
12 12 5.4
13 13 4.0
14 14 2.7
15 15 1.34
16 16 0.67
Table 1: AAT3103-1 LED Current Settings,
RSET = 14.3kΩ.
S2C Wire Interface Data Code
Dx LED Current (mA)
0
5
10
15
20
25
12345678910111213141516
Figure 2: AAT3103-1 Current Control Profile,
RSET = 14.3kΩ.
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Data EN Rising Edges D1-D3 Current (mA)
1 1 20.1
2 2 17.5
3 3 14.8
4 4 12.1
5 5 9.4
6 6 6.7
7 7 4.0
8 8 1.34
Table 2: AAT3103-2 LED Current Settings,
RSET = 14.3kΩ.
S2C Wire Interface Data Code
Dx LED Current (mA)
0
5
10
15
20
25
12 34 5 6 78
Figure 3: AAT3103-2 Current Control Profile,
RSET = 14.3kΩ.
PWM Control (AAT3103-4 only)
PWM (Pulse Width Modulation) is a technique of control-
ling LED brightness by modulating the conduction duty
cycle of the LED current. LED brightness is determined by
the PWM duty cycle and FS (Full Scale) and LSB (the least
LED current). The FS LED current is determined by RSET
.
The LSB LED current value is equal to the FS value divid-
ed by 30. A PWM control signal can be applied into the
EN/PWM pin of the AAT3103-4. By changing the duty
cycle of the PWM signal from 100% (logic high) to 10%,
the LED current can be programmed from 20mA to
2.6mA. To save power when not used, the AAT3103-4 can
be shut down by holding the EN/PWM pin low for 500s.
Lastly, Table 3 and Figure 4 illustrate the AAT3103-4’s
LED current control profile as a function of a PWM con-
trol signal.
EN/PWM Duty Cycle D1-D3 Current (mA)
100% 20.2
90% 18.2
80% 16.2
70% 14.3
60% 12.3
50% 10.4
40% 8.5
30% 6.55
20% 4.6
10% 2.6
Table 3: AAT3103-4 LED Current Settings,
RSET = 14.3kΩ, fPWM = 25kHz.
PWM Duty Cycle (%)
Dx LED Current (mA)
0
5
10
15
20
25
1
0
2030405060708090100
Figure 4: AAT3103-4 Current Control Profile,
RSET = 14.3kΩ, fPWM = 25kHz.
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Applications Information
LED Selection
The AAT3103 is specifically intended for driving WLEDs.
However, the device design will allow the AAT3103 to
drive most types of LEDs with forward voltage specifica-
tions ranging from 2.2V to 4.7V. LED applications may
include mixed arrangements for display backlighting,
keypad display, and any other application needing a con-
stant current sink generated from a varying input volt-
age. Since the D1 to D3 constant current sources are
matched with negligible supply voltage dependence, the
constant current channels will be matched regardless of
the specific LED forward voltage (VF) levels.
The internal charge pump and low dropout current
sources in the AAT3103 maximize performance and
make it capable of driving LEDs with high forward volt-
ages. Multiple channels can be combined to obtain a
higher LED drive current without complication.
Constant Current Setting
The LED full scale current is controlled by the RSET resis-
tor. The following formula can be used to calculate the
AAT3103-1/2/4 full scale LED current:
ILED_FS = · 4 · 60
1.2
RSET
Table 4 shows the RSET resistor value for the AAT3103-1/2/4
for various LED full-scale current levels. For maximum
accuracy, a 1% tolerance resistor is recommended.
ILED_FS (mA) RSET (kΩ)
30.2 9.53
20.1 14.3
15.1 19.1
10.0 28.7
Table 4: Maximum LED Current and RSET Resistor
Values (1% Resistor Tolerance) for the AAT3103.
The S2C interface rising edges control the LED current
from full scale to the LSB. For the AAT3103-1, 16 steps
are employed. Figure 5 shows the LED current of the
AAT3103-1 at different RSET values.
S2C Wire Interface Data Code
Dx LED Current (mA)
0
5
10
15
20
25
30
35
12345678910111213141516
RSET = 9.53k
RSET = 14.3k
RSET = 19.1k
RSET = 28.7k
Figure 5: AAT3103-1 LED Current Control Profile
at Different RSET Values.
Use the following formula to calculate the AAT3103-3 full
scale LED current:
ILED_FS = · 4 · 48
1.2
RSET
For example, an 11.5k 1% resistor is used to achieve
20mA full scale LED current operation.
Device Switching Noise Performance
The AAT3103 operates at a fixed frequency of approxi-
mately 0.9MHz to control noise and limit harmonics that
can interfere with the RF operation of mobile communi-
cation devices. Back-injected noise appearing on the
input pin of the charge pump is 20mV peak-to-peak,
typically ten times less than inductor-based DC/DC boost
converter WLED backlight solutions. The AAT3103's soft-
start feature prevents noise transient effects associated
with inrush currents during start-up of the charge pump
circuit.
Shutdown
To activate the shutdown operation, the EN/SET input for
the AAT3103-1/-2 should be pulsed low for longer than
tOFF (500s). For the 3103-4 PWM options, shutdown
operation is enabled when the EN/PWM input is pulsed
low longer than 500s. In this state, the AAT3103 typi-
cally draws less than 1A from the input. Registers are
reset to 0 in shutdown.
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Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the following
sections accounts only for efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT3103, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT3103 outputs are pure constant current
sources and typically drive individual loads, it is difficult
to measure the output voltage for a given output pin to
derive an overall output power measurement. For any
given application, WLED forward voltage levels can dif-
fer, 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 WLED
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
WLED 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 AAT3103 efficiency may be quantified under very
specific conditions and is dependent upon the input volt-
age versus the outputs of D1, D2 and D3 for a given
constant current setting. Depending on the combination
of VIN and voltages sensed at the current sources, the
device will operate in load switch mode. When any one of
the voltages sensed at the current sources nears drop-
out, the device will operate in 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.
1x Mode Efficiency
The AAT3103 1x mode is operational at all times and
functions alone to enhance device power conversion effi-
ciency when VIN is higher than the voltage across the
load. When in 1x mode, voltage conversion efficiency is
defined as output power divided by input power.
η = PF
PIN
The ideal efficiency (η) in 1x charge-pump mode can be
expressed as:
POUT
PIN
VF · ILED
VIN · IIN
VF · ILED
VIN · IOUT
VF
VIN
η = = = ≈
-or-
VF
VIN
η (%) = · 100
For a charge pump LED driver with VF of 3.2V and 4.2V
input voltage, the theoretical efficiency is 76%. Due to
internal switching losses and IC quiescent current con-
sumption, the actual efficiency can be measured at 73%.
2x Charge Pump Mode Efficiency
The AAT3103 contains a charge pump which will boost
the input supply voltage in the event where VIN is less
than the voltage required to supply the output. The effi-
ciency () can be simply defined as a linear voltage
regulator with an effective output voltage that is equal
to one half of the input voltage. Efficiency () for an
ideal 2x charge pump can typically be expressed as the
output power divided by the input power.
η = PF
PIN
In addition, with an ideal 2x charge pump, the output
current may be expressed as 1/3 of the input current.
The expression to define the ideal efficiency (η) can be
rewritten as
POUT
PIN
VF · ILED
VIN · IIN
VF · ILED
VIN · 2 · IOUT
VF
2 · VIN
η = = = ≈
-or-
VF
2 · VIN
η (%) = · 100
For a charge pump LED current source driver with VF of
3.2V and 2.7V input voltage, the theoretical efficiency is
59%. Due to internal switching losses and IC quiescent
current consumption, the actual efficiency can be mea-
sured at 57%. Efficiency will decrease substantially as
load current drops below 1mA or when the voltage level
at VIN approaches the voltage level at VOUT
.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3103.2008.03.1.0 13
www.analogictech.com
Additional Applications
The current sources of the AAT3103 can be combined to
drive higher current levels through a single LED. As an
example, a single LED can be driven at 60mA total by
combining together the D1-D3 outputs as shown in
Figure 6.
For lower-cost applications, the flying capacitor can be
removed. This will force the AAT3103 to operate in 1x
mode. To maintain regulated LED current, the input supply
voltage must be greater than the charge pump’s dropout
voltage and the current source voltage drop in 1x mode.
For example, to power 3.0V VF with 20mA LED current, VIN
should be greater than 4.0V as shown in Figure 7.
Capacitor Selection
Careful selection of the three external capacitors CIN, CP
,
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 three capacitors is a good starting point when
choosing capacitors.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended
over all other types of capacitors for use with the AAT3103.
Ceramic capacitors offer many advantages over their tan-
talum 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 tran-
sient response. Since ceramic capacitors are non-polar-
ized, they are not prone to incorrect connection damage.
U1
AAT3103
C1
1μF
D1
1D2 10
OUT
2
C-
3
4C+
5IN
D3
AGND
RSET
EN/SET
9
8
7
6
VIN
C2
1μF
C3
1μF
D1
R1
14.3k
EN/SET
Figure 6: Higher Current, Single LED Application.
U1
AAT3103
D1
1D2 10
OUT
2
C-
3
4C+
5IN
D3
AGND
RSET
EN/SET
9
8
7
6
C2
1μF
C3
1μF
D2D3
R1
14.3k
VIN
EN/SET
D1
Figure 7: Lower Cost 1x Mode Application.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
14 3103.2008.03.1.0
www.analogictech.com
Evaluation Board Schematic
U1
AAT3103-1
C1
1μF
D1
1D2 10
OUT
2
C-
3
4C+
5IN
D3
AGND
RSET
EN/SET
9
8
7
6
VCC
JP1
123
DC+DC-
C
10μF
U2
PIC12F675
VDD
1
GP5
2
3GP4
4GP3
VSS
GP0
GP1
GP2
8
7
6
5
R7
330Ω
LED2
Red
R4
1k
R3
1k
R5
1k
R6
330Ω
LED1
Green
CYCLE
DOWN
UP
AAT3103-1
White LED
Driver
S2Cwire
Microcontroller
C2
1μF
C3
1μF
JP2 JP3 JP4
D1D2D3
R1
14.3k
SW
1VOUT 5
SHDN
4GND 2
VIN
6FB 3
U4
AAT1217-3.3
L1
4.7μH
C5
4.7μF
R8 10k
C6
4.7μF
JP5
R2
20k
VR1
POT10K
C4
0.1μF
S1
S2
S3
+
Figure 8: AAT3103 Evaluation Board Schematic.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3103.2008.03.1.0 15
www.analogictech.com
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3103.2008.03.1.0 15
www.analogictech.com
Evaluation Board Layout
Figure 9: AAT3103 Evaluation Board Figure 10: AAT3103 Evaluation Board
Component Side PCB Layout. Solder Side PCB Layout.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
16 3103.2008.03.1.0
www.analogictech.com
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
16 3103.2008.03.1.0
www.analogictech.com
Ordering Information
Package Interface Current Control, Inverting Marking1Part Number (Tape and Reel)2
SC70JW-10 S2Cwire 16-step 1DXYY AAT3103IJQ-1-T1
SC70JW-10 S2Cwire 8-step AAT3103IJQ-2-T1
SC70JW-10 PWM Linear 2TXYY AAT3103IJQ-4-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/about/quality.aspx.
Package Information
SC70JW-10
0.45
±
0.10
0.05
±
0.05
2.10
±
0.30
4
°
±
4
°
0.15
±
0.05
2.00
±
0.20
7
°
±
3
°
0.85
±
0.15
1.10 MAX
0.100
0.225
±
0.075
1.75
±
0.10
2.20
±
0.20
0.40 BSC
Top View
Side View End View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3103.2008.03.1.0 17
www.analogictech.com
AAT3103
3-Channel Charge-Pump LED DriverChargePumpTM
PRODUCT DATASHEET
3103.2008.03.1.0 17
www.analogictech.com
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Fax (408) 737-4611
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