AAT AAT3103

PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
General Description
Features
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 automatically switch between 1x mode and 2x mode to maintain the highest efficiency and optimal LED current accuracy and matching. A low external parts count (one 1μF
flying capacitor, two small 1μF capacitors at IN and OUT
and one current setting resistor) makes the AAT3103 ideally 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
1μA. Built-in soft-start circuitry prevents excessive inrush
current during start-up. Integrated short circuit and thermal protection circuitry protects the device from damage.
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
•
•
•
•
The AAT3103 is available in a 2x2.1mm thermally
enhanced Pb-free 10-lead SC70JW-10 package.
Cordless Phone Handsets
Mobile Phone Handsets
MP3 and PMP Players
Digital Cameras
Typical Application
Input Voltage
2.7V to 5.5V
IN
C+
C IN
1μF
CP
1μF
OUT
AAT3103-1
C OUT
1μF
C-
EN/SET
S2Cwire
Interface
D1
RSET
D3
D2
RSET
14.3kΩ
3103.2008.03.1.0
EN/SET
AGND
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WLEDs
OSRAM LW M 678
or equivalent
1
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Pin Descriptions
Pin #
Symbol
1
2
3
4
D1
OUT
CC+
5
IN
EN/SET
(AAT3103-1/-2)
6
EN/PWM
(AAT3103-4)
7
RSET
8
9
10
AGND
D3
D2
Description
LED1 Current Source Output. Connect LED1’s anode to D1 and its cathode to AGND.
Charge Pump Output. Bypass OUT to AGND with a 1μF or larger ceramic capacitor.
Charge Pump Capacitor Negative Node.
Charge Pump Capacitor Positive Node. Connect a 1μF ceramic capacitor between C+ and C-.
Power source input. Connect IN to the power source, typically the battery. Bypass IN to AGND with a
1μF or larger ceramic capacitor.
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.
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.
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 14.3kΩ resistor sets each full-scale
output current to 20mA.
Analog Ground. Connect this pin to the system’s analog ground plane.
LED3 Current Source Output. Connect LED3’s anode to D3 and its cathode to AGND.
LED2 Current Source Output. Connect LED2’s anode to D2 and its cathode to AGND.
Pin Configuration
SC70JW-10
(Top View)
2
D1
1
10
D2
OUT
2
9
D3
C-
3
8
AGND
C+
4
7
RSET
IN
5
6
EN/SET (EN/PWM)
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3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Absolute Maximum Ratings1
Symbol
TJ
TLEAD
Description
IN, C+, C-, OUT, D1, D2, D3, and RSET Pin Voltages to AGND
EN/SET or EN/PWM Pin Voltage to AGND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
-0.3 to 6.0
-0.3 to VIN + 0.3
-40 to 150
300
V
V
°C
°C
Value
Units
625
160
mW
°C/W
Thermal Information
Symbol
PD
ΘJA
Description
Maximum Power Dissipation
Maximum Thermal Resistance2
2, 3
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.
3103.2008.03.1.0
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3
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Electrical Characteristics1
IN = EN = 3.6V; CIN = 1μF; COUT = 1μF; CCP = 1μF; RSET = 14.3kΩ; TA=-40°C to 85°C unless otherwise noted. Typical
values are at TA = 25°C.
Symbol
Description
Conditions
Input Power Supply
IN
Input Voltage Range
IIN
Input Operating Current
Min
Typ
Max
Units
5.5
10
V
7.4
1.9
3
mA
4
6.8
1
μA
2.7
IN = 5.5V; EN = IN; VD1 = VD2 = VD3 = 0V
IN = 5.5V; EN = IN; ID1 = ID2 = ID3 = FS,
excluding ID1-ID3; VD1 = VD2 = VD3 = IN – 1.5V
Operating, ID1 = ID2 = ID3 = OPEN
EN/SET or EN/PWM = GND
IIN(SHDN)
Input Shutdown Current
Charge Pump Section
OUT Maximum Output Current
IOUT
fOSC
Charge Pump Oscillator Frequency
VIN_(TH)
Charge Pump Mode Hysteresis
ID1 = ID2 = ID3 = 20mA
tOUT
LED Output Current Start-up Time
EN/SET or EN/PWM = IN
AAT3103-1/-2/-4: LED Current Source Outputs
ID_(MAX)
D1 - D3 Current Accuracy
DATA = 1; VIN – VF = 1.5V.
ΔID_(MAX)
D1 - D3 Current Matching
DATA = 1; VIN – VF = 1.5V
D1 - D3 Current Accuracy
ID_(DATA15)
DATA = 15; VIN – VF = 1.5V
(AAT3103-1 only)
D1 - D3 Current Accuracy
ID_(DATA8)
DATA = 8; VIN – VF = 1.5V
(AAT3103-2 only)
D1 - D3 Current Accuracy
DC = 10%; VIN – VF = 1.5V
ID_(10%)
(AAT3103-4 only)
D1- D3 Charge Pump Mode
VD_(TH)
ID1 = ID2 = ID3 = 20mA
Transition Threshold
VSET
RSET Pin Voltage
AAT3103-1/-2: EN/SET and S2Cwire Control
VENH
EN/SET Input High Threshold Voltage
VENL
EN/SET Input Low Threshold Voltage
IEN(LKG)
EN/SET Input Leakage Current
EN/SET = IN = 5V
tEN/SET(OFF)
EN/SET Input OFF Timeout
tEN/SET(LAT)
EN/SET Input Latch Timeout
tEN/SET(LOW) EN/SET Input Low Time
tENSET(H-MIN) EN/SET Minimum High Time
tENSET(H-MAX) EN/SET Maximum High Time
AAT3103-4: EN/PWM Current Control
VENH
EN/PWM Input High Threshold Voltage
VENL
EN/PWM Input Low Threshold Voltage
IEN(LKG)
EN/PWM Input Leakage Current
EN/PWM = IN = 5V
PWM Control Turn-on Delay
tPWM(ON)
tEN/PWM
EN/PWM Input OFF Timeout
fPWM
PWM Control Frequency
Duty cycle = 80%
0.65
100
0.9
325
150
1.4
mA
MHz
mV
μs
18
20
±3
22
mA
%
1.0
1.34
1.61
mA
1.0
1.34
1.61
mA
1.14
2.5
mA
280
mV
1.18
1.22
1.4
0.4
1
500
500
75
-1
0.3
50
75
1.4
0.4
1
-1
110
0.15
1
50
V
V
V
μA
μs
μs
μs
ns
μs
V
V
μA
μs
ms
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.
4
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3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Typical Characteristics
Shutdown Current vs. Temperature
Operating Current vs. Input Voltage
(VD1 = VD2 = VD3 = 0V)
0.07
8.0
0.06
7.0
6.0
IQ (mA)
ISHDN (µA)
0.05
0.04
0.03
0.02
5.0
4.0
3.0
2.0
0.01
VIN = 5.5V
VIN = 2.7V
0.00
-40
-15
10
35
60
-40°C
25°C
85°C
1.0
0.0
2.5
85
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Temperature (°C)
LED Current Matching vs. Temperature
Operating Current vs. Input Voltage
4.2
21.0
4.1
20.5
Current (mA)
IQ (mA)
(No Load; D1, D2, D3 Open)
3.9
3.8
3.6
2.5
85°C
25°C
-40°C
3
3.5
4
4.5
5
20.0
19.5
19.0
-40
5.5
D1
D2
D3
-15
10
35
60
85
28
33
Temperature (°C)
Input Voltage (V)
Efficiency vs. Input Voltage
ILED Full Scale vs. RSET
35
100
90
28
70
ILED (mA)
Efficiency (%)
80
60
50
40
30
ILED = 30mA,VF = 3.5V
ILED = 20mA,VF = 3.2V
ILED = 10mA,VF = 3.0V
20
10
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
21
14
7
5.5
0
8
Input Voltage (V)
3103.2008.03.1.0
13
18
23
RSET (kΩ)
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5
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Typical Characteristics
EN Input Low Threshold Voltage
vs. Input Voltage
1.2
1.2
1.0
1.0
0.8
0.8
VENL (V)
VENH (V)
EN Input High Threshold Voltage
vs. Input Voltage
0.6
-40°C
25°C
85°C
0.4
0.2
2.7
3.1
3.5
3.9
4.3
4.7
5.1
0.6
-40°C
25°C
85°C
0.4
0.2
2.7
5.5
3.1
3.5
Input Voltage (V)
EN/SET Input Latch Timeout
vs. Input Voltage
tEN/SET(OFF) (V)
tEN/SET(LAT) (V)
5.1
5.5
350
250
200
85°C
25°C
-40°C
150
100
2.7
3.1
3.5
3.9
4.3
4.7
5.1
300
250
200
85°C
25°C
-40°C
150
100
2.7
5.5
3.1
Input Voltage (V)
VOUT
(5V/div)
2.7V
3.2V
4.3
4.7
5.1
5.5
(VIN = 3.6V; 20mA/Dx)
EN/SET
(2V/div)
4.2V
3.9
Turn-Off from 2X Mode
(VIN = 3.6V; 20mA/Dx)
0V
3.5
Input Voltage (V)
Turn-On to 2X Mode
0V
VD1
(2V/div)
0V
IIN
(200mA/div)
0A
Time (200µs/div)
6
4.7
400
300
VD1
(2V/div)
IIN
(200mA/div)
4.3
EN/SET Input Off Timeout
vs. Input Voltage
350
EN/SET
(2V/div)
3.9
Input Voltage (V)
0A
Time (100µs/div)
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3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Typical Characteristics
Turn-On to 1X Mode
Output Ripple Waveform
(VIN = 4.2V; 20mA/Dx)
EN/SET
(2V/div)
0V
VOUT
(2V/div)
0V
VD1
(2V/div)
IIN
(200mA/div)
0V
(2X Mode; 20mA/Dx)
VOUT (AC)
(20mV/div)
0A
0V
VIN
(20mV/div)
0V
VD1
(20mV/div)
0V
Time (200µs/div)
Time (1µs/div)
LED Current Transition
LED Current Transition
(VIN = 4.2V; 1.3mA to 20mA)
EN/SET
(2V/div)
0V
VOUT
(2V/div)
VD1
(2V/div)
IIN
(50mA/div)
(VIN = 4.2V; 20mA to 1.3mA)
EN/SET
(2V/div)
4.2V
2.7V
0V
4.2V
VOUT
(2V/div)
3.2V
3.2V
VD1
(2V/div)
IIN
(50mA/div)
0A
Time (100µs/div)
2.7V
0A
Time (100µs/div)
Input Current vs. Input Voltage
Input Current (mA)
250
ILED = 30mA
ILED = 20mA
ILED = 10mA
200
150
VIN Rising
VIN Falling
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
Input Voltage (V)
3103.2008.03.1.0
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PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Functional Block Diagram
C+
IN
C–
OUT
Two-Mode
CP Control
D1
D2
VF Monitoring
3
D3
AGND
IREF
EN/SET
(EN/PWM)
S2Cwire Control
(PWM Control)
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 voltage levels necessary to drive the LEDs. LED current is
individually controlled through integrated current sources 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 1μF ceramic capacitor for the charge pump flying
capacitors (CP), one 1μF ceramic input capacitor (CIN),
one 1μF ceramic output capacitor (COUT) and a resistor
8
DAC
RSET
(RSET) to set the maximum LED current. The three constant 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 14.3kΩ 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.
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PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Part Number Descriptions
Part Number
Interface
Current Control,
Inverting
AAT3103IJQ-1
AAT3103IJQ-2
AAT3103IJQ-4
S2Cwire
S2Cwire
PWM
16-step
8-step
Linear
changed quickly and easily. Also the non-pulsating LED
current reduces system noise and improves LED reliability. 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 (500μs).
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 (500μs), the AAT3103 enters into
shutdown mode and draws less than 1μA from the input
and the internal data register is reset to zero.
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, allowing the user to “set it and forget it.” With its high-speed
serial interface (1MHz data rate), the LED current can be
The AAT3103-1/-2’s serial interface reduces the LED current 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 current. 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. .
THI
TLO
TOFF
TLAT
EN/SET
1
2
n-1
Data Reg
n ≤ 16
0
n-1
0
Figure 1: S2Cwire Serial Interface Timing.
EN Rising Edges
D1-D3 Current (mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
20.1
18.8
17.5
16.1
14.8
13.4
12.1
10.7
9.4
8.1
6.7
5.4
4.0
2.7
1.34
0.67
25
Dx LED Current (mA)
S2C Data
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
S2C Wire Interface Data Code
Figure 2: AAT3103-1 Current Control Profile,
RSET = 14.3kΩ.
Table 1: AAT3103-1 LED Current Settings,
RSET = 14.3kΩ.
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PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Data
EN Rising Edges
D1-D3 Current (mA)
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
20.1
17.5
14.8
12.1
9.4
6.7
4.0
1.34
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 500μs.
Lastly, Table 3 and Figure 4 illustrate the AAT3103-4’s
LED current control profile as a function of a PWM control signal.
EN/PWM Duty Cycle
D1-D3 Current (mA)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
20.2
18.2
16.2
14.3
12.3
10.4
8.5
6.55
4.6
2.6
Table 2: AAT3103-2 LED Current Settings,
RSET = 14.3kΩ.
Dx LED Current (mA)
25
20
15
10
Table 3: AAT3103-4 LED Current Settings,
RSET = 14.3kΩ, fPWM = 25kHz.
5
0
1
2
3
4
5
6
7
8
25
2
Figure 3: AAT3103-2 Current Control Profile,
RSET = 14.3kΩ.
PWM Control (AAT3103-4 only)
PWM (Pulse Width Modulation) is a technique of controlling 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 divided by 30. A PWM control signal can be applied into the
EN/PWM pin of the AAT3103-4. By changing the duty
10
Dx LED Current (mA)
S C Wire Interface Data Code
20
15
10
5
0
100
90
80
70
60
50
40
30
20
10
PWM Duty Cycle (%)
Figure 4: AAT3103-4 Current Control Profile,
RSET = 14.3kΩ, fPWM = 25kHz.
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3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
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 specifications ranging from 2.2V to 4.7V. LED applications may
include mixed arrangements for display backlighting,
keypad display, and any other application needing a constant current sink generated from a varying input voltage. 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 voltages. 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 resistor. The following formula can be used to calculate the
AAT3103-1/2/4 full scale LED current:
ILED_FS =
1.2
· 4 · 60
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
20.1
15.1
10.0
9.53
14.3
19.1
28.7
RSET = 9.53k
30
RSET = 14.3k
25
20
RSET = 19.1k
15
RSET = 28.7k
10
5
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
S2C Wire Interface Data Code
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 =
1.2
· 4 · 48
RSET
For example, an 11.5kΩ 1% resistor is used to achieve
20mA full scale LED current operation.
Device Switching Noise Performance
The AAT3103 operates at a fixed frequency of approximately 0.9MHz to control noise and limit harmonics that
can interfere with the RF operation of mobile communication 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 softstart feature prevents noise transient effects associated
with inrush currents during start-up of the charge pump
circuit.
Shutdown
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.
3103.2008.03.1.0
Dx LED Current (mA)
35
To activate the shutdown operation, the EN/SET input for
the AAT3103-1/-2 should be pulsed low for longer than
tOFF (500μs). For the 3103-4 PWM options, shutdown
operation is enabled when the EN/PWM input is pulsed
low longer than 500μs. In this state, the AAT3103 typically draws less than 1μA from the input. Registers are
reset to 0 in shutdown.
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11
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
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 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 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 ideal efficiency (η) in 1x charge-pump mode can be
expressed as:
POUT VF · ILED VF · ILED VF
≈
η= P = V ·I =V ·I
VIN
IN
IN
IN
IN
OUT
-or-
VF
η (%) = V · 100
IN
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 consumption, 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 efficiency (η) 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 (η) for an
ideal 2x charge pump can typically be expressed as the
output power divided by the input power.
The AAT3103 efficiency may be quantified under very
specific conditions and is dependent upon the input voltage 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 dropout, the device will operate in 2x charge pump mode.
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
Each of these modes will yield different efficiency values.
Refer to the following two sections for explanations for
each operational mode.
POUT VF · ILED
VF · ILED
VF
η= P = V ·I =V ·2·I
≈2·V
IN
IN
IN
IN
OUT
IN
The AAT3103 1x mode is operational at all times and
functions alone to enhance device power conversion efficiency 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.
12
PF
PIN
-or-
1x Mode Efficiency
η=
η=
PF
PIN
VF
η (%) = 2 · V · 100
IN
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 measured 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.
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3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Additional Applications
performance will be obtained when low equivalent series
resistance (ESR) ceramic capacitors are used; in general,
low ESR may be defined as less than 100mΩ. A value of
1μF for all three capacitors is a good starting point when
choosing capacitors.
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.
Capacitor Characteristics
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.
Ceramic composition capacitors are highly recommended
over all other types of capacitors for use with the AAT3103.
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.
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
D1
C2
1μF
1
2
C1
1μF
3
4
5
VIN
U1
AAT3103
D1
D2
OUT
D3
9
8
CC+
IN
10
AGND
7
RSET
EN/SET
6
R1
14.3k
C3
1μF
EN/SET
Figure 6: Higher Current, Single LED Application.
C2
1μF
1
2
3
4
5
VIN
U1
AAT3103
D1
OUT
C-
10
D2
9
D3
AGND
8
D3
D2
D1
7
RSET
6
EN/SET
C+
IN
R1
14.3k
C3
1μF
EN/SET
Figure 7: Lower Cost 1x Mode Application.
3103.2008.03.1.0
www.analogictech.com
13
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Evaluation Board Schematic
DC-
DC+
AAT3103-1
White LED
Driver
+
C
10μF
VCC
C2
1μF
1 2 3
D3
JP2
1
JP1
2
C1
1μF
3
4
5
U1
AAT3103-1
JP3
D2
D1
JP4
10
D1
D2
OUT
C-
D3
8
AGND
9
7
RSET
6
EN/SET
C+
IN
C3
1μF
R1
14.3k
JP5
S2Cwire
Microcontroller
R2
20k
L1
4.7μH
1
6
4
U4
AAT1217-3.3
SW
VIN
SHDN
VOUT
FB
GND
5
3
2
C6
4.7μF
R5
1k
R8 10k
C5
4.7μF
R4
1k
R3
1k
S1
UP
S2
DOWN
1
2
3
4
U2
PIC12F675
VDD
VSS
GP5
GP0
GP4
GP1
GP3
GP2
C4
0.1μF
8
VR1
POT10K
7
6
5
R7
330Ω
LED2
Red
R6
330Ω
S3
CYCLE
LED1
Green
Figure 8: AAT3103 Evaluation Board Schematic.
14
www.analogictech.com
3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Evaluation Board Layout
Figure 9: AAT3103 Evaluation Board
Component Side PCB Layout.
3103.2008.03.1.0
Figure 10: AAT3103 Evaluation Board
Solder Side PCB Layout.
www.analogictech.com
15
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Ordering Information
Package
Interface
Current Control, Inverting
Marking1
Part Number (Tape and Reel)2
SC70JW-10
SC70JW-10
SC70JW-10
S Cwire
S2Cwire
PWM
16-step
8-step
Linear
1DXYY
AAT3103IJQ-1-T1
AAT3103IJQ-2-T1
AAT3103IJQ-4-T1
2
2TXYY
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
2.20 ± 0.20
1.75 ± 0.10
0.40 BSC
0.225 ± 0.075
Top View
0.100
7° ± 3°
0.45 ± 0.10
4° ± 4°
0.05 ± 0.05
0.15 ± 0.05
1.10 MAX
0.85 ± 0.15
2.00 ± 0.20
2.10 ± 0.30
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.
16
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3103.2008.03.1.0
PRODUCT DATASHEET
AAT3103
ChargePumpTM
3-Channel Charge-Pump LED Driver
Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© 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. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to
support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other
brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
3103.2008.03.1.0
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17