AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
2803.2006.04.1.5
1
ChargePump
TM
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
CwireTM
(Advanced Simple Serial ControlTM) 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 50A for optimized efficien-
cy, with a low housekeeping current of only 50A.
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 1A.
The AAT2803 is available in a Pb-free, space-saving,
thermally enhanced 24-pin 4x4mm QFN package
and is rated over the -40C to +85C temperature
range.
Features
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
(50A) 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
<1A 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
AAT2803
C
IN
1
F
V
IN
C1
1
F
D2
GND
Backlight
C2
1
F
C3
1
F
C2
+
C
OUT
1
F
ENFL
EN/SET
VIN
EN_FL
Flash
EN/SET
C2
-
C1
+
C1
-
C3
+
C3
-
VOUT
D3
D2
D1
D4
D5
D6
D1
D3
D4
D5
D6
C
OUT
1
F
Pin Descriptions
Pin Configuration
QFN44-24
(Top View)
1
3
2
5
4
6
18
16
17
14
15
13
10
11
12
8
9
7
19
21
20
23
22
24
C1-
C1+
VOUT_FL
VIN
EN_FL
N/C
N/C
VOUT_B
L
C2+
C3+
C3-
C2-
GND
D1
VIN
GND
D2
D3
AAT2803
D5
D4
D6
EN/SET
N/C
GND
Pin #
Symbol
Function
1
C1-
Flying capacitor 1 negative terminal.
2
C1+
Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-.
3
VOUT_FL
Flash output voltage. Requires 1F capacitor connected between this pin and ground.
4, 14
VIN
Input power supply. Requires 1F capacitor connected between this pin and ground.
5
EN_FL
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 1A of current.
6, 7, 23
N/C
No connect.
8
VOUT_BL
Backlight output voltage charge pump. Requires 1F capacitor connected between this
pin and ground.
9
C2+
Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-.
10
C3+
Flying capacitor 3 positive terminal. Connect a 1F capacitor between C3+ and C3-.
11
C3-
Flying capacitor 3 negative terminal.
12
C2-
Flying capacitor 2 negative terminal.
13, 15, 24
GND
Ground.
16
D1
Current sink input #1.
17
D2
Current sink input #2.
18
D3
Current sink input #3.
19
D5
Current sink input #5.
20
D4
Current sink input #4.
21
D6
Current sink input #6.
22
EN/SET
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.
EP
Exposed paddle (bottom); connect to GND directly beneath package.
AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
2
2803.2006.04.1.5
Absolute Maximum Ratings
1
Thermal Information
2
Symbol
Description
Value
Units
P
D
Maximum Power Dissipation
3
2.0
W
JA
Maximum Thermal Resistance
50
C/W
Symbol
Description
Value
Units
V
IN
Input Voltage
-0.3 to 6
V
V
EN/SET
EN/SET to GND Voltage
-0.3 to V
IN
+ 0.3
V
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
2803.2006.04.1.5
3
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 25C.
Electrical Characteristics
1
V
IN
= 3.6V, C
IN
= C
OUT
= C
1
= C
2
= C
3
= 1.0F; T
A
= -40C to +85C, unless otherwise noted.
Typical values are T
A
= 25C.
Symbol
Description
Conditions
Min
Typ Max Units
V
IN
Operation Range
2.7
5.5
V
1X Mode, 3.0
V
IN
5.5, Active,
0.3
1
No Load Current; EN/SET = V
IN
;
EN_FL= GND
1.5X Mode, 3.0
V
IN
5.5, Active,
1.0
3.0
No Load Current; EN/SET = V
IN
;
EN_FL= GND
mA
I
CC
Operating Current
2X Mode, 3.0
V
IN
5.5, Active,
2.0
3.7
No Load Current; EN/SET = V
IN
;
EN_FL = GND
V
OUT_FLASH
= 5V; EN/SET = GND;
2.0
4.5
EN_FL = V
IN
50A Setting, 1X Mode; EN/SET
50
A
= V
IN
; EN_FL = GND
I
SHDN
Shutdown Current
EN/SET = 0
1.0
A
I
DX
I
SINK
Average Current Accuracy
2
I
SET
= 30mA, T
A
= 25C
27
30
33
mA
I
SET
= 4.1mA, T
A
= 25C
3.69
4.1
4.51
I
(D-Match)
Current Matching Between Any
V
F
:D1:D4 = 3.6V
0.5
%
Two Current Sink Inputs
3, 4
V
TH
1X to 1.5X or 1.5X to 2X Transition
150
mV
Threshold at Any D
X
Pin
V
OUT
Output Voltage (Flash Charge
3.0< V
IN
< 5V, I
OUT
= 120mA;
4.3
4.5
4.7
V
Pump)
5
EN_FL = V
IN
Max Continuous Output Current
V
IN
= 3.3V; V
OUT
= 4.5V;
120
I
OUT
(Flash Charge Pump)
5
EN_FL = V
IN
mA
Max Pulsed Output Current
5
V
IN
= 3.6V; V
OUT
= 4.5V;
300
I
PULSED
= 250ms
T
SS
Soft-Start Time
Backlight Charge Pump
100
s
Flash Charge Pump
200
F
CLK
Clock Frequency
1.0
MHz
V
EN(L)
Enable Threshold Low
V
IN
= 2.7V
0.4
V
V
EN(H)
Enable Threshold High
V
IN
= 5.5V
1.4
V
AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
4
2803.2006.04.1.5
1. The AAT2803 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. 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.
Electrical Characteristics
1
V
IN
= 3.6V, C
IN
= C
OUT
= C
1
= C
2
= C
3
= 1.0F; T
A
= -40C to +85C, unless otherwise noted.
Typical values are T
A
= 25C.
Symbol
Description
Conditions
Min
Typ Max Units
T
EN/SET LO
EN/SET Low Time
0.3
75
s
T
EN/SET_HI_MIN
Minimum EN/SET High Time
50
ns
T
EN/SET_HI_MAX
Maximum EN/SET High Time
75
s
T
OFF
EN/SET Off Timeout
500
s
T
LAT
EN/SET Latch Timeout
500
s
I
EN/SET;EN_FL
Input Leakage
V
EN/SET;EN_FL
= 5V; V
IN
= 5V
-1.0
1.0
A
AAT2803
Six-Channel White LED Backlight
Charge Pump with Flash
2803.2006.04.1.5
5
1. The AAT2803 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
PDF 
ZIP