AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2806.2006.04.1.8
1
ChargePump
TM
General Description
The AAT2806 is a dual charge pump designed to
support both the white LED backlight and flash appli-
cations for systems operating with lithium-ion/poly-
mer batteries. The backlight charge pump is capable
of driving up to four LEDs at a total of 80mA. The cur-
rent sinks may be operated individually 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 automati-
cally selected by comparing the forward voltage of
each LED with the input voltage. AnalogicTech's
S
2
CwireTM (Simple Serial ControlTM) serial digital
input is used to enable, disable, and set current for
each LED with an eight-level logarithmic scale plus
four low-current settings down to 50A for optimized
efficiency, with a typical operating quiescent current
of less than 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
250mA of pulsed current. It has an independent
enable pin for improved power savings.
The AAT2806 has thermal protection and built-in
soft-start circuitry. A low-current shutdown feature
disconnects the load from V
IN
and reduces quiescent
current to less than 1A.
The AAT2806 is available in a Pb-free, space-saving,
thermally-enhanced TDFN44-16 package and is
rated over the -40C to +85C temperature range.
Features
V
IN
Range: 2.7V to 5.5V
Dual Charge Pump to Support Backlight and
Flash LEDs
Backlight Charge Pump:
-- Regulated Current
-- Four Current Sink Inputs
-- S
2
Cwire Brightness Control
-- Tri-Mode Charge Pump
-- Maximum 20mA of Current Per Input
-- Low I
Q
(50A) in Light Load Mode
Flash Charge Pump:
-- Regulated Output Voltage
-- Up to 250mA of Pulsed Current
Independent Backlight/Flash Control
Low Noise 1MHz Constant Frequency
Operation
Automatic Soft Start
No Inductors
Available in TDFN44-16 Package
Applications
Color (RGB) Lighting
White LED Backlighting
White LED Photo Flash
Typical Application
AAT2806
C
IN
1F
V
IN
C
OUT
1F
EN/SET
C1
1F
D3
D2
D1
VIN
C1+ C1- C2+ C2- C3+ C3-
D2
GND
Backlight
C2
1F
C3
1F
Flash
VOUT_FL
VOUT_BL
C
OUT
1F
EN_FLSH
EN/SET
EN_FLSH
D1
D3
D4
V
OUT_FLASH
D4
Pin Descriptions
Pin Configuration
TDFN44-16
(Top View)
VOUT_FL
VIN
D4
C3-
C3+
3
D3
D2
D1
C2+
VOUT_BL
C1-
EN_FLSH
C2-
C1+
EN/SET
GND
4
5
1
2
6
7
8
14
13
12
16
15
11
10
9
Pin #
Symbol
Function
1
C3-
Flying capacitor 3 negative terminal.
2
C3+
Flying capacitor 3 positive terminal. Connect a 1F capacitor between C3+ and C3-.
3
VOUT_FL
Regulated output voltage for the flash LED. Requires 1F capacitor connected between
this pin and ground.
4
VIN
Input power supply. Requires 1F capacitor connected between this pin and ground.
5
D4
Current sink input 4.
6
D3
Current sink input 3.
7
D2
Current sink input 2.
8
D1
Current sink input 1.
9
GND
Ground.
10
EN/SET
S
2
Cwire serial interface control pin. It is used to enable/disable the backlight charge
pump and to control the brightness of the white LEDs.
11
C1+
Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-.
12
C1-
Flying capacitor 1 negative terminal.
13
VOUT_BL
Regulated output voltage for the white LEDs. Requires 1F capacitor connected
between this pin and ground.
14
C2+
Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-.
15
C2-
Flying capacitor 2 negative terminal.
16
EN_FLSH
Enable/disable pin for the flash charge pump.
EP
Exposed paddle (bottom); connect to GND directly beneath package.
AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2
2806.2006.04.1.8
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 6.0
V
V
EN/SET
; EN_FL
EN/SET; EN_FL to GND Voltage
-0.3 to V
IN
+ 0.3
V
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2806.2006.04.1.8
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
Input Power Supply
V
IN
Operation Range
2.7
5.5
V
1X Mode, 3.0
V
IN
5.5, Active, No Load
0.3
1
Current; EN_FLSH = GND, EN/SET = V
IN
1.5X Mode, 3.0
V
IN
5.5, Active, No Load
1.0
3.0
Current; EN_FLSH = GND, EN/SET = V
IN
mA
I
CC
Operating Current
2X Mode, 3.0
V
IN
5.5, Active, No Load
2.0
3.7
Current; EN_FLSH = GND, EN/SET = V
IN
EN_FLSH = GND, 50A Output Setting,
50
A
1X Mode
3.0
V
IN
5.5, No Load Current;
2.0
4.5
mA
EN_FLSH = V
IN
, EN/SET = GND
I
SHDN
Shutdown Current
EN_FLSH = EN/SET = 0
1.0
A
I
DX
Input Current Accuracy
2, 3
I
SET
= 20mA and I
SET
= 4.1mA; T
A
= 25C
-10
10
%
I
(D-Match)
Current Matching Between Any VD1:D4 = 3.6V, V
IN
= 3.5V
0.5
%
Two Current Sink Inputs
2, 4
R
SINK
Sink Switch Impedance (each)
2
7
3.0V < V
IN
< 5V, I
OUT
= 100mA;
4.32 4.5 4.68
V
OUT_FL
Flash Charge Pump Output
EN_FLSH = V
IN
V
Voltage
5
3.0V < V
IN
< 5V, I
OUT
= 150mA;
4.3 4.5
4.7
EN_FLSH = V
IN
I
OUT_FL
Maximum Continuous I
OUT
5
V
IN
= 3.6V; V
OUT
= 4.5V; EN_FLSH = V
IN
120
mA
Maximum Pulsed I
OUT
5
V
IN
= 3.6V; V
OUT
= 4.5V; I
PULSED
< 500ms
250
T
SS
Soft-Start Time
100
s
F
CLK
Clock Frequency
1.0
MHz
V
EN(L)
Enable Threshold Low
0.4
V
V
EN(H)
Enable Threshold High
1.4
V
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
I
Enable and EN/SET Input
-1.0
1.0
A
Leakage
AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
4
2806.2006.04.1.8
1. The AAT2806 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. Specification applies only to the tri-mode charge pump.
3. Determined by the average of all active channels.
4. Current matching is defined as the deviation of any sink current from the average of all active channels.
5. Specification applies only to the charge pump doubler.
Typical Characteristics Flash Driver Charge Pump Section
Load Response vs. Time
(100mA Load)
Time (5ms/div)
V
OUT_FL
(10mV/div)
I
OUT
(50mA/div)
V
IN
= 3.5V
Load Response vs. Time
(50mA Load)
Time (5ms/div)
V
OUT_FL
(10mV/div)
I
OUT
(20mA/div)
V
IN
= 3.5V
Start-Up Time
(100mA Load)
Time (100s/div)
EN_FLSH
(1V/div)
V
OUT_FL
(1V/div)
Start-Up Time
(50mA Load)
Time (100s/div)
EN_FLSH
(1V/div)
V
OUT_FL
(1V/div)
Maximum Current Pulse vs. Supply Voltage
(V
OUT_FL
= 4.5V; EN_FL = V
IN
; EN/SET = GND)
Supply Voltage (V)
Maximum Current Pulse (mA)
0
50
100
150
200
250
300
350
400
450
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
One-shot pulse duration = 250ms
V
OUT
> 4.0V
Output Voltage vs. Output Current
(V
OUT_FL
= 4.5V; EN_FL = V
IN
; EN/SET = GND)
Output Current (mA)
Output Voltage (V)
4.40
4.44
4.48
4.52
4.56
4.60
0.1
1.0
10.0
100.0
1000.0
3.6V
3.0V
3.3V
2.7V
AAT2806
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2806.2006.04.1.8
5
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