Multi-Mode Charge Pump for
White LED Backlight and Flash Applications
General Description
The AAT2801 is a member of AnalogicTech's Total
Power Management IC™ (TPMIC™) product family.
It has a dual charge pump architecture designed to
support both the white LED backlight and flash appli-
cations for systems operating with Lithium-Ion bat-
teries. The backlight charge pump provides power
required to drive up to four LEDs. To maximize
power efficiency, it automatically selects 1X, 1.5X, or
2X mode. The device produces current levels up to
30mA on each of its four current source outputs.
AnalogicTech's Simple Serial Control™ (S
2
Cwire™)
interface is used to enable, disable, and set the LED
drive current with a 32-level logarithmic scale LED
brightness control.
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 AAT2801 is equipped with AnalogicTech’s
AutoBias™ technology which allows individual LEDs
to be powered either by charge pump or battery
input, determined internally and automatically to
maximize the power efficiency even with a large dif-
ference in LED forward voltage.
The AAT2801 has thermal protection and built-in
soft-start circuitry. A high charge pump switching fre-
quency enables the use of very small external capac-
itors. The AAT2801 is available in the 16-pin
TDFN44 package.
AAT2801
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
ChargePump
™
V
IN
Range: 2.7V to 5.5V
Dual Charge Pump
— Flash: Charge Pump Doubler
— Backlight: Tri-Mode Charge Pump
Drives Low-V
F
and High-V
F
LEDs
Up to Four 30mA Outputs
32-Position Logarithmic Scale with Digital
Control
Low Noise Constant Frequency Operation
1MHz Switching Frequency
AutoBias Technology
Regulated 4.5/5.0 Volts V
OUT_FLASH
Up to 250mA of Current for Flash
Automatic Soft Start
No Inductors
I
Q
<1µA in Shutdown
Available in 16-pin TDFN44 Package
Applications
•
•
•
•
Display Modules
Mobile Phones
PDAs
Smart Phones
Typical Application
C1
1μF
C2
1μF
C3
1μF
C1
+
IN
C1
-
C2
+
C2
-
C3
+
C3
-
C
F
1μF
CP
V
IN
C
IN
1μF
C
CP
1μF
R
B
OUT_FLSH
Flash LED
AAT2801
D1
D2
D3
D4
D4
D3
D2
Backlight
D1
EN/SET
Flash Enable
EN/SET
EN_FLSH
GND
2801.2006.04.1.3
1
Multi-Mode Charge Pump for
White LED Backlight and Flash Applications
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
EP
AAT2801
Symbol
C3-
C3+
OUT_FLASH
IN
C1+
C1-
CP
C2+
C2-
GND
EN/SET
D3
D1
D4
D2
EN_FLSH
Function
Flying capacitor 3 negative terminal. Connect a 1µF capacitor between C3- and C3+.
Flying capacitor 3 positive terminal.
Flash output voltage. Requires 1µF capacitor connected between this pin and ground.
Input power supply. Requires 1µF capacitor connected between this pin and ground.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Flying capacitor 1 negative terminal.
White LED charge pump output. Requires 1µF capacitor connected between this pin
and ground.
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C3-.
Flying capacitor 2 negative terminal.
Ground.
S
2
Cwire serial interface control pin for the white LED charge pump. This pin should not
be left floating.
Current source output #3.
Current source output #1.
Current source output #4.
Current source output #2.
Active high enable pin for the flash charge pump. When connected low, the charge
pump shuts down and consumes less than 1µA of current.
Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
TDFN44-16
(Top View)
C3-
C3+
OUT_FLASH
IN
C1+
C1-
CP
C2+
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
EN_FLSH
D2
D4
D1
D3
EN/SET
GND
C2-
2
2801.2006.04.1.3
Multi-Mode Charge Pump for
White LED Backlight and Flash Applications
Absolute Maximum Ratings
1
Symbol
V
IN
V
EN/SET
I
OUT
2
T
J
AAT2801
Description
Input Voltage
EN/SET to GND Voltage
Maximum DC Output Current
Operating Junction Temperature Range
Value
-0.3 to 6.0
-0.3 to V
IN
+0.3
120
-40 to 150
Units
V
V
mA
°C
Thermal Information
Symbol
P
D
θ
JA
Description
Maximum Power Dissipation
3, 4
Thermal Resistance
3
Value
2.0
50
Units
mW
°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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 6.25mW/°C above 25°C.
2801.2006.04.1.3
3
Multi-Mode Charge Pump for
White LED Backlight and Flash Applications
Electrical Characteristics
1
C
IN
= C
CP
= C
F
= C1 = C2 = C3 = 1.0µF; T
A
= -40°C to 85°C, unless otherwise noted.
Symbol
Description
Conditions
Min Typ Max Units
2.7
-
5.5
4.5
V
AAT2801
Input Power Supply
V
IN
Operation Range
I
CC
Operating Current
I
SHDN
I
DX
I
(D-Match)
V
OUT
Shutdown Current
Output Current Accuracy
2
Current Matching
3
Flash Charge Pump Output
Voltage
Maximum Continuous I
OUT
I
OUT
Maximum Pulsed I
OUT
η
CP
White LED Charge Pump
Section Efficiency
Charge Pump Section
T
SS
F
CLK
EN/SET
V
EN(L)
V
EN(H)
T
EN/SET LO
T
EN/SET HI MIN
T
EN/SET HI MAX
T
OFF
T
LAT
I
EN/SET/EN_FLSH
Soft-Start Time
Clock Frequency
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
Minimum EN/SET High Time
Maximum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
Input Leakage
3.0
≤
V
IN
≤
5.5, No Load Current; V
OUT_FLSH
= 5V, EN/SET = GND, EN_FLSH = V
IN
3.0
≤
V
IN
≤
5.5, EN/SET = V
IN
, EN_FLSH =
GND, VD1:VD4 = 2.0V, CP = 1X
3.0
≤
V
IN
≤
5.5, No Load Current; EN/SET =
-
V
IN
, EN_FLSH = GND, CP = 1.5X
EN_FLSH = EN/SET = 0
-
V
IN
= 3.5, Code = 32, T
A
= 25°C
-10
VD1:D4 = 3.6, V
IN
= 3.5V; LED Charge
-3.0
Pump Only
3.0V < V
IN
< 5V, I
OUT
= 120mA;
4.3
EN_FLSH = V
IN
V
IN
= 3.6V; V
OUT
= 4.5V; EN_FLSH = V
IN
120
V
IN
= 3.6V; V
OUT
= 4.5V; I
Pulsed
< 500mS
250
V
IN
= 3.5V, I
OUT(TOTAL)
= 120mA,
Measured from IN to CP
Backlight Charge Pump
Flash Charge Pump
3.0
0.55
3.0
mA
5.0
1.0
10
3.0
4.7
-
-
µA
%
%
V
mA
%
±0.5
4.5
93
50
200
1.0
-
1.4
0.3
50
-
-
-
-1.0
75
500
500
1.0
0.4
-
75
µs
MHz
V
V
µs
µs
µs
µs
µs
µA
V
EN/SET
< 0.6V
V
EN/SET
> 1.4V
V
EN/SET
> 1.4V
V
EN/SET
< 0.6V
V
EN/SET
> 1.4V
V
EN/SET/EN_FLSH
= 5V, V
IN
= 5V
1. The AAT2801 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. Codes 2 through 7 are guaranteed to be within ±15% of stated current level.
3. Current matching is defined as I
(D-Match)
= (I
D
- I
AVE
)/I
AVE
.
4
2801.2006.04.1.3
Multi-Mode Charge Pump for
White LED Backlight and Flash Applications
Typical Characteristics–White LED Backlight Driver Section
V
IN
= 3.5V, C
IN
= 2.2µF, C
CP
= C1 = C2 = 1.0µF; T
A
= 25°C, unless otherwise noted.
AAT2801
Efficiency vs. V
IN
(Code 26)
100
90
100
90
Efficiency vs. V
IN
(D1 = 3.5V; D2 = 3.3V; D3 = 3.2V; D4 = 3.0V)
Efficiency (%)
Efficiency (%)
80
70
60
50
40
30
2.9
3.0
3.1
3.0V
F
80
70
60
50
40
30
Code 26
3.5V
F
Code 28
2.9
3.0
3.1
3.2
Code 32
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
Input Voltage (V)
Input Voltage (V)
Efficiency vs. V
IN
(D1-D2 = 3.5V; D3-D4 = 3.2V)
100
90
5.0
Operating Current
(Code 23; EN_FLSH Off)
Code 26
Efficiency (%)
80
4.0
3.0
2.0
1.0
V_D
X
= 3.3V
60
50
40
30
2.9
Code 28
3.0
3.1
3.2
Code 32
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
I
IN
(A)
70
V_D
X
= 3.0V
0.0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Input Voltage (V)
Input Voltage (V)
Operating Current
(Code 23; EN_FLSH On; I
OUT
= 100mA)
8.0
7.0
6.0
V_D
X
= 3.3V
I
IN
(A)
5.0
4.0
3.0
2.0
1.0
0.0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
V_D
X
= 3.0V
Input Voltage (V)
2801.2006.04.1.3
5
MCU
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