AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2805.2005.05.1.2
1
ChargePump
TM
General Description
The AAT2805 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 120mA. The
current sinks may be operated individually or in par-
allel 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 selected 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, dis-
able, and set current for each LED with a 16-level
logarithmic scale plus four low-current settings down
to 50A for optimized efficiency, with a typical oper-
ating 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 AAT2805 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 AAT2805 is available in a space-saving, ther-
mally-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
-- AS
2
Cwire Brightness Control
-- Tri-Mode Charge Pump
-- Maximum 30mA 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
AAT2805
C
IN
1
F
V
IN
C
OUT
1
F
EN/SET
C1
1
F
D3
D2
D1
VIN
C1+ C1- C2+ C2- C3+ C3-
D2
GND
Backlight
C2
1
F
C3
1
F
Flash
VOUT_FL
VOUT_BL
C
OUT
1
F
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 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
AS
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 white LED. 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.
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2
2805.2005.05.1.2
Absolute Maximum Ratings
1
Thermal Information
Symbol
Description
Value
Units
P
D
Maximum Power Dissipation
2, 3
2.0
W
JA
Maximum Thermal Resistance
2
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
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2805.2005.05.1.2
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 at 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
1.0
3.0
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, 4
I
SET
= 30mA; T
A
= 25C
-10
10
%
I
(D-Match)
Current Matching Between Any
VD1:D4 = 3.6, V
IN
= 3.5V
0.5
%
Two Current Sink Inputs
2, 5
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
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
V
IN
= 3.6V; V
OUT
= 4.5V; EN_FLSH = V
IN
120
mA
Maximum Pulsed I
OUT
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
V
EN/SET
< 0.6V
0.3
75
s
T
EN/SET HI
Minimum EN/SET High Time
V
EN/SET
> 1.4V
50
ns
T
OFF
EN/SET Off Timeout
V
EN/SET
< 0.6V
500
s
T
LAT
EN/SET Latch Timeout
V
EN/SET
> 1.4V
500
s
I
I
Enable and EN/SET Input
V
EN/SET
= V
EN_FLSH
= V
IN
-1.0
1.0
A
Leakage
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
4
2805.2005.05.1.2
1. The AAT2805 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. Specification applies only to the charge pump doubler.
4. Determined by the sum of all active channels
5. Current matching is defined as the deviation of any sink current from the average of all active channels.
Typical CharacteristicsFlash Driver Charge Pump Section
Load Response vs. Time
(100mA Load)
5ms/div
V
OUT_FL
(10mV/div)
I
OUT
(50mA/div)
V
IN
= 3.5V
Load Response vs. Time
(50mA Load)
5ms/div
V
OUT_FL
(10mV/div)
I
OUT
(20mA/div)
V
IN
= 3.5V
Startup Time
(100mA Load)
100
s/div
EN_FLSH
(1V/div)
V
OUT_FL
(1V/div)
Startup Time
(50mA Load)
100
s/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
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
2805.2005.05.1.2
5
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