High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
General Description
The AAT3155 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-
mode load switch (1X), fractional (1.5X), and dou-
bling (2X) conversion to maximize efficiency for
white LED applications. The AAT3155 is capable of
driving up to four channels of LEDs at 20mA per
channel from a 2.7V to 5.5V input. The current
sinks may be operated individually or in parallel for
driving higher current LEDs. A low external parts
count (two 1µF flying capacitors and two small 1µF
capacitors at IN and OUTCP) make this part ideal-
ly suited for small, battery-powered applications.
AnalogicTech's S
2
Cwire
™
(Simple Serial Control
™
)
serial digital input is used to enable, disable, and set
current for each LED with 16 settings down to 50μA.
The low-current mode supply current can be as low
as 50μA to save power.
Each output of the AAT3155 is equipped with built-
in protection for output short-circuit and auto-dis-
able for load short-circuit conditions. Built-in soft-
start circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature dis-
connects the load from the input and reduces qui-
escent current to less than 1μA.
The AAT3155 is available in a Pb-free, space-sav-
ing 2.85x3.0mm 12-pin TSOPJW package.
AAT3155
Features
•
•
•
•
•
•
•
•
•
•
•
•
ChargePump
™
V
IN
Range: 2.7V to 5.5V
Fully Programmable Current with Single Wire
— 16 Current Levels
— Four Low Current Settings Down to 50µA
Low I
Q
(50µA) for Low Current Mode
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives up to Four Channels of LEDs
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Automatic Soft Start
I
Q
<1µA in Shutdown
2.85x3.0mm TSOPJW-12 Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
C1+
C1
1µF
C2+
C2
1µF
C1-
2.7V to 5.5V
C
IN
1µF
C2-
OUTCP
C
OUT
1µF
IN
AAT3155
GND
D1
D2
D1
D2
D3
D4
EN/SET
EN/SET
D3
D4
3155.2006.05.1.1
1
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
AAT3155
Symbol
D3
D2
D1
GND
IN
C2-
C2+
OUTCP
C1-
C1+
EN/SET
D4
Function
Current sink input #3.
Current sink input #2.
Current sink input #1.
Ground.
Input power supply. Requires 1µF capacitor connected between this pin and
ground.
Flying capacitor 2 negative terminal.
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and
C2-.
Charge pump output to drive load circuit. Requires 1µF capacitor connected
between this pin and ground.
Flying capacitor 1 negative terminal.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and
C1-.
S
2
Cwire serial interface control pin.
Current sink input #4.
Pin Configuration
TSOPJW-12
(Top View)
D3
D2
D1
GND
IN
C2-
1
2
3
4
5
6
12
11
10
9
8
7
D4
EN/SET
C1+
C1-
OUTCP
C2+
2
3155.2006.05.1.1
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Absolute Maximum Ratings
1
Symbol
V
IN
V
EN/SET
I
OUT
2
T
J
T
LEAD
AAT3155
Description
Input Voltage to GND
EN/SET Voltage to GND
Maximum DC Output Current
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
-0.3 to 6
-0.3 to V
IN
+ 0.3
150
-40 to 150
300
Units
V
V
mA
°C
°C
Thermal Information
3
Symbol
P
D
θ
JA
Description
Maximum Power Dissipation
4
Maximum Thermal Resistance
Value
0.625
160
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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 6.25mW/°C above 25°C.
3155.2006.05.1.1
3
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Electrical Characteristics
1
C
IN
= C
OUT
= C
1
= C
2
= 1.0µF; T
A
= -40°C to +85°C, unless otherwise noted.
Typical values are T
A
= 25°C, V
IN
= 3.6V.
Symbol
Description
Conditions
Min
2.7
1X Mode, 3.0
≤
V
IN
≤
5.5, Active,
No Load Current
1.5X Mode, 3.0
≤
V
IN
≤
5.5, Active,
No Load Current
2X Mode, 3.0
≤
V
IN
≤
5.5, Active,
No Load Current
50µA Setting, 1X Mode
V
EN/SET
= 0V
I
SET
= 20mA, T
A
= 25°C
V
F
:D1:D4=3.6V
0.3
1
1
50
18
20
0.5
150
100
1000
0.4
1.4
0.3
50
75
500
500
1
75
1
22
1
µA
µA
mA
%
mV
µs
kHz
V
V
µs
ns
µs
µs
µs
µA
AAT3155
Typ
Max
5.5
1
3
Units
V
Input Power Supply
V
IN
Operation Range
I
CC
Operating Current
mA
Shutdown Current
I
SINK
Average Current Accuracy
I
(D-Match)
Current Matching
2
1X to 1.5X or 1.5X to 2X Transition
V
TH
Threshold at Any I
SINK
Pin
Charge Pump Section
T
SS
Soft-Start Time
F
CLK
Clock Frequency
EN/SET
V
EN(L)
Enable Threshold Low
V
IN
= 2.7V
V
EN(H)
Enable Threshold High
V
IN
= 5.5V
T
EN/SET LO
EN/SET Low Time
T
EN/SET_HI_MIN
Minimum EN/SET High Time
T
EN/SET_HI_MAX
Maximum EN/SET High Time
T
OFF
EN/SET Off Timeout
T
LAT
EN/SET Latch Timeout
I
EN/SET
EN/SET Input Leakage
I
SHDN
I
DX
-1
1. The AAT3155 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. Current matching is defined as the deviation of any sink current from the average of all active channels.
4
3155.2006.05.1.1
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