AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
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
Cwire™ (Advanced Simple Serial
Control™) 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 50µA for optimized efficiency, with a typical oper-
ating quiescent current of less than 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
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 1µA.
The AAT2805 is available in a space-saving, ther-
mally-enhanced TDFN44-16 package and is rated
over the -40°C to +85°C temperature range.
Features
•
•
•
ChargePump
™
•
•
•
•
•
•
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
(50µA) 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
C1
1µF
C2
1µF
C3
1µF
C1+ C1- C2+ C2- C3+ C3-
VOUT_FL
VIN
V
IN
C
OUT
1µF
V
OUT_FLASH
Flash
AAT2805
C
IN
1µF
VOUT_BL
Backlight
D1
EN/SET
EN_FLSH
EN/SET
EN_FLSH
D1
D2
D3
D4
D2
D3
D4
C
OUT
1µF
GND
2805.2005.05.1.2
1
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
EP
Symbol
C3-
C3+
VOUT_FL
VIN
D4
D3
D2
D1
GND
EN/SET
C1+
C1-
VOUT_BL
C2+
C2-
EN_FLSH
Function
Flying capacitor 3 negative terminal.
Flying capacitor 3 positive terminal. Connect a 1µF capacitor between C3+ and C3-.
Regulated output voltage for flash LED. Requires 1µF capacitor connected between this
pin and ground.
Input power supply. Requires 1µF capacitor connected between this pin and ground.
Current sink input 4.
Current sink input 3.
Current sink input 2.
Current sink input 1.
Ground.
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.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Flying capacitor 1 negative terminal.
Regulated output voltage for white LED. Requires 1µF capacitor connected between this
pin and ground.
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-.
Flying capacitor 2 negative terminal.
Enable/disable pin for the flash charge pump.
Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
TDFN44-16
(Top View)
C3-
C3+
VOUT_FL
VIN
D4
D3
D2
D1
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
EN_FLSH
C2-
C2+
VOUT_BL
C1-
C1+
EN/SET
GND
2
2805.2005.05.1.2
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
Absolute Maximum Ratings
1
Symbol
V
IN
V
EN/SET
; EN_FL
T
LEAD
Description
Input Voltage
EN/SET; EN_FL to GND Voltage
Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6.0
-0.3 to V
IN
+ 0.3
300
Units
V
V
°C
Thermal Information
Symbol
P
D
θ
JA
Description
Maximum Power Dissipation
2, 3
Maximum Thermal Resistance
2
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.
2805.2005.05.1.2
3
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
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 at T
A
= 25°C.
Symbol
V
IN
Description
Operation Range
Conditions
Min Typ Max Units
2.7
5.5
1
3.0
3.0
µA
4.5
1.0
10
0.5
7
4.5
4.5
mA
µA
%
%
Ω
4.68
4.7
V
V
Input Power Supply
I
CC
Operating Current
I
SHDN
I
DX
I
(D-Match)
R
SINK
V
OUT_FL
Shutdown Current
Input Current Accuracy
2, 4
Current Matching Between Any
Two Current Sink Inputs
2, 5
Sink Switch Impedance (each)
2
Flash Charge Pump Output
Voltage
Maximum Continuous I
OUT
Maximum Pulsed I
OUT
Soft-Start Time
Clock Frequency
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
Minimum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
Enable and EN/SET Input
Leakage
1X Mode, 3.0
≤
V
IN
≤
5.5, Active, No Load
Current; EN_FLSH = GND, EN/SET = V
IN
1.5X Mode, 3.0
≤
V
IN
≤
5.5, Active, No Load
Current; EN_FLSH = GND, EN/SET = V
IN
2X Mode, 3.0
≤
V
IN
≤
5.5, Active, No Load
Current; EN_FLSH = GND, EN/SET = V
IN
EN_FLSH = GND, 50µA Output Setting,
1X Mode
3.0
≤
V
IN
≤
5.5, No Load Current;
EN_FLSH = V
IN
, EN/SET = GND
EN_FLSH = EN/SET = 0
I
SET
= 30mA; T
A
= 25°C
VD1:D4 = 3.6, V
IN
= 3.5V
0.3
1.0
1.0
50
2.0
mA
-10
I
OUT_FL
T
SS
F
CLK
V
EN(L)
V
EN(H)
T
EN/SET LO
T
EN/SET HI
T
OFF
T
LAT
I
I
3.0V < V
IN
< 5V, I
OUT
= 100mA;
EN_FLSH = V
IN
3.0V < V
IN
< 5V, I
OUT
= 150mA;
EN_FLSH = V
IN
V
IN
= 3.6V; V
OUT
= 4.5V; EN_FLSH = V
IN
V
IN
= 3.6V; V
OUT
= 4.5V; I
PULSED
< 500mS
4.32
4.3
120
250
mA
100
1.0
0.4
µs
MHz
V
V
µs
ns
µs
µs
µA
V
EN/SET
V
EN/SET
V
EN/SET
V
EN/SET
V
EN/SET
<
>
<
>
=
0.6V
1.4V
0.6V
1.4V
V
EN_FLSH
= V
IN
1.4
0.3
50
75
500
500
1.0
-1.0
1. The AAT2805 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. 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.
4
2805.2005.05.1.2
AAT2805
Dual High Efficiency Charge Pump
for White LED and Flash Applications
Typical Characteristics–Flash Driver Charge Pump Section
Output Voltage vs. Output Current
(V
OUT_FL
= 4.5V; EN_FL = V
IN
; EN/SET = GND)
4.60
Maximum Current Pulse vs. Supply Voltage
(V
OUT_FL
= 4.5V; EN_FL = V
IN
; EN/SET = GND)
Maximum Current Pulse (mA)
450
400
350
300
250
200
150
100
50
0
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
Output Voltage (V)
One-shot pulse duration = 250ms
V
OUT
> 4.0V
4.56
4.52
4.48
3.6V
3.0V
4.44
3.3V
2.7V
4.40
0.1
1.0
10.0
100.0
1000.0
Output Current (mA)
Supply Voltage (V)
Startup Time
(50mA Load)
Startup Time
(100mA Load)
EN_FLSH
(1V/div)
EN_FLSH
(1V/div)
V
OUT_FL
(1V/div)
V
OUT_FL
(1V/div)
100µs/div
µ
100µs/div
µ
Load Response vs. Time
(50mA Load)
V
IN
= 3.5V
V
OUT_FL
(10mV/div)
V
OUT_FL
(10mV/div)
Load Response vs. Time
(100mA Load)
V
IN
= 3.5V
I
OUT
(20mA/div)
I
OUT
(50mA/div)
5ms/div
5ms/div
2805.2005.05.1.2
5
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