Six-Channel White LED Backlight
Charge Pump with Flash
General Description
The AAT2803 is a dual charge pump designed to sup-
port both white LED backlight and flash applications
for systems operating with lithium-ion/polymer batter-
ies. The backlight charge pump is capable of driving
up to six LEDs at a total of 180mA. The current sinks
may be operated in group or in parallel for driving
higher current LEDs. To maximize power efficiency,
the charge pump operates in 1X, 1.5X, or 2X mode,
where the mode of operation is automatically select-
ed by comparing the forward voltage of each LED
with the input voltage. AnalogicTech's AS
2
Cwire™
(Advanced Simple Serial Control™) serial digital input
is used to enable, disable, and set current for each
LED with a 16-level logarithmic scale plus four low-
current settings down to 50μA for optimized efficien-
cy, with a low housekeeping current of only 50μA.
The flash charge pump is a charge pump doubler
with a regulated output voltage. It is designed to
deliver 120mA of continuous current and up to
300mA of pulsed current. It has an independent
enable pin for improved power savings.
The AAT2803 is equipped with built-in protection,
short-circuit, and auto-disable for load short-circuit
condition. Built-in soft-start circuitry prevents exces-
sive inrush current during start-up. A low-current
shutdown feature disconnects the load from V
IN
and
reduces quiescent current to less than 1μA.
The AAT2803 is available in a Pb-free, space-saving,
thermally enhanced 24-pin 4x4mm QFN package
and is rated over the -40°C to +85°C temperature
range.
AAT2803
Features
•
•
•
ChargePump
™
•
•
•
•
•
•
•
•
V
IN
Range: 2.7V to 5.5V
Dual Charge Pump:
— Flash: Charge Pump Doubler
— Backlight: Tri-Mode Charge Pump
Backlight Charge Pump:
— Programmable Current With Single GPIO
— 16 Current Steps
— 15/20/30mA Max Current
— Four Low Current Settings
— Individual Main/Sub-Group Control
— Low I
Q
(50μA) for Low-Current Mode
— Drives Six Channels of LEDs
Flash Charge Pump:
— Regulated V
OUT_FL
4.5/5.0 Volts
— Up to 300mA of Current for Flash
1MHz Constant Switching Frequency
Independent Backlight/Flash Control
Built-In Thermal Protection
Built-In Auto-Disable for Open Circuit
Automatic Soft Start
I
Q
<1μA in Shutdown
Available in QFN44-24 Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sink
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
C1
1μF
C2
1μF
C3
1μF
C1
+
VIN
V
IN
C
IN
1μF
C1
-
C2
+
C2
-
C3
+
C3
-
VOUT
C
OUT
1μF
Flash
AAT2803
D6
D5
D4
D3
D2
Backlight
D1
EN_FL
ENFL
C
OUT
1μF
EN/SET
EN/SET
GND
D6
D5
D4
D3
D2
D1
2803.2006.04.1.5
1
Six-Channel White LED Backlight
Charge Pump with Flash
Pin Descriptions
Pin #
1
2
3
4, 14
5
6, 7, 23
8
9
10
11
12
13, 15, 24
16
17
18
19
20
21
22
EP
AAT2803
Symbol
C1-
C1+
VOUT_FL
VIN
EN_FL
N/C
VOUT_BL
C2+
C3+
C3-
C2-
GND
D1
D2
D3
D5
D4
D6
EN/SET
Function
Flying capacitor 1 negative terminal.
Flying capacitor 1 positive terminal. Connect a 1μF capacitor between C1+ and C1-.
Flash output voltage. Requires 1μF capacitor connected between this pin and ground.
Input power supply. Requires 1μF capacitor connected between this pin and ground.
Enable pin for flash charge pump. For normal operation, connect to V
IN
. When con-
nected low, the flash charge pump shuts down and consumes less than 1μA of current.
No connect.
Backlight output voltage charge pump. Requires 1μF capacitor connected between this
pin and ground.
Flying capacitor 2 positive terminal. Connect a 1μF capacitor between C2+ and C2-.
Flying capacitor 3 positive terminal. Connect a 1μF capacitor between C3+ and C3-.
Flying capacitor 3 negative terminal.
Flying capacitor 2 negative terminal.
Ground.
Current sink input #1.
Current sink input #2.
Current sink input #3.
Current sink input #5.
Current sink input #4.
Current sink input #6.
AS
2
Cwire serial interface control pin for backlight charge pump. It controls the current
settings for all six channels. This pin should not be left floating.
Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
QFN44-24
(Top View)
D5
D4
D6
EN/SET
N/C
GND
24
23
22
21
20
19
C1-
C1+
VOUT_FL
VIN
EN_FL
N/C
1
2
3
4
5
6
18
17
AAT2803
16
15
14
13
D3
D2
D1
GND
VIN
GND
10
11
12
7
8
9
C2-
C3-
C3+
C2+
VOUT_BL
N/C
2
2803.2006.04.1.5
Six-Channel White LED Backlight
Charge Pump with Flash
Absolute Maximum Ratings
1
Symbol
V
IN
V
EN/SET
T
J
T
LEAD
AAT2803
Description
Input Voltage
EN/SET to GND Voltage
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6
-0.3 to V
IN
+ 0.3
-40 to 150
300
Units
V
V
°C
°C
Thermal Information
2
Symbol
P
D
θ
JA
Description
Maximum Power Dissipation
3
Maximum Thermal Resistance
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 condi-
tions 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 board.
3. Derate 6.25mW/°C above 25°C.
2803.2006.04.1.5
3
Six-Channel White LED Backlight
Charge Pump with Flash
Electrical Characteristics
1
V
IN
= 3.6V, C
IN
= C
OUT
= C
1
= C
2
= C
3
= 1.0μF; T
A
= -40°C to +85°C, unless otherwise noted.
Typical values are T
A
= 25°C.
Symbol
V
IN
AAT2803
Description
Operation Range
Conditions
1X Mode, 3.0
≤
V
IN
≤
5.5, Active,
No Load Current; EN/SET = V
IN
;
EN_FL= GND
1.5X Mode, 3.0
≤
V
IN
≤
5.5, Active,
No Load Current; EN/SET = V
IN
;
EN_FL= GND
2X Mode, 3.0
≤
V
IN
≤
5.5, Active,
No Load Current; EN/SET = V
IN
;
EN_FL = GND
V
OUT_FLASH
= 5V; EN/SET = GND;
EN_FL = V
IN
50μA Setting, 1X Mode; EN/SET
= V
IN
; EN_FL = GND
EN/SET = 0
I
SET
= 30mA, T
A
= 25°C
I
SET
= 4.1mA, T
A
= 25°C
V
F
:D1:D4 = 3.6V
Min
2.7
Typ
Max Units
5.5
V
0.3
1
1.0
3.0
mA
I
CC
Operating Current
2.0
2.0
50
27
3.69
30
4.1
0.5
150
3.7
4.5
μA
1.0
33
4.51
μA
mA
%
mV
4.7
V
I
SHDN
I
DX
I
(D-Match)
V
TH
V
OUT
Shutdown Current
I
SINK
Average Current Accuracy
2
Current Matching Between Any
Two Current Sink Inputs
3, 4
1X to 1.5X or 1.5X to 2X Transition
Threshold at Any D
X
Pin
Output Voltage (Flash Charge
Pump)
5
Max Continuous Output Current
(Flash Charge Pump)
5
Max Pulsed Output Current
5
I
OUT
T
SS
F
CLK
V
EN(L)
V
EN(H)
Soft-Start Time
Clock Frequency
Enable Threshold Low
Enable Threshold High
3.0< V
IN
< 5V, I
OUT
= 120mA;
EN_FL = V
IN
V
IN
= 3.3V; V
OUT
= 4.5V;
EN_FL = V
IN
V
IN
= 3.6V; V
OUT
= 4.5V;
I
PULSED
= 250ms
Backlight Charge Pump
Flash Charge Pump
V
IN
= 2.7V
V
IN
= 5.5V
4.3
120
4.5
mA
300
100
200
1.0
0.4
1.4
μs
MHz
V
V
1. The AAT2803 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.
2. Determined by the average of all active channels.
3. Current matching is defined as the deviation of any sink current from the average of all active channels.
4. Specification applies only to the tri-mode charge pump.
5. Specification applies only to the charge pump doubler.
4
2803.2006.04.1.5
Six-Channel White LED Backlight
Charge Pump with Flash
Electrical Characteristics
1
V
IN
= 3.6V, C
IN
= C
OUT
= C
1
= C
2
= C
3
= 1.0μF; T
A
= -40°C to +85°C, unless otherwise noted.
Typical values are T
A
= 25°C.
Symbol
T
EN/SET LO
T
EN/SET_HI_MIN
T
EN/SET_HI_MAX
T
OFF
T
LAT
I
EN/SET;EN_FL
AAT2803
Description
EN/SET Low Time
Minimum EN/SET High Time
Maximum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
Input Leakage
Conditions
Min
0.3
Typ
50
Max Units
75
75
500
500
1.0
μs
ns
μs
μs
μs
μA
V
EN/SET;EN_FL
= 5V; V
IN
= 5V
-1.0
1. The AAT2803 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.
2803.2006.04.1.5
5
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