General Description
The AAT3156 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 AAT3156 is capable of
driving six-channel LEDs at a total of 180mA from
a 2.7V to 5.5V input. The current sinks may be
operated individually or in parallel for driving high-
er-current LEDs. A low external parts count (two
1F flying capacitors and two small 1F capacitors
at V
IN
and V
OUT
) make this part ideally suited for
small battery-powered applications.
AnalogicTech's AS
2
CwireTM (Advanced Simple
Serial ControlTM) serial digital input is used to
enable, disable, 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 low housekeeping current of only 50A.
Each output of the AAT3156 is equipped with built-
in protection for V
OUT
short circuit and auto disable
for LED failure condition. Built-in soft-start circuitry
prevents excessive inrush current during start-up.
A low current shutdown feature disconnects the
load from V
IN
and reduces quiescent current to less
than 1A.
The AAT3156 is available in a space-saving, ther-
mally-enhanced 16-pin 4x4mm QFN package.
Features
V
IN
Range: 2.7V to 5.5V
Fully Programmable Current with Single Wire
-- 16-Step Logarithmic Scale
-- 15/20/30mA Max Current
-- Four Low Current Settings Down to 50A
-- Low I
Q
(50A) for Low Current Mode
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives Six Channels of LEDs
Individual Main/Sub-Group Control
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Built-In Auto-Disable For Open Circuit
Automatic Soft-Start
I
Q
<1A in Shutdown
Thermally-Enhanced QFN44-16 Package
Applications
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for DSCs
AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Application
C1
1
F
C2
1
F
D1
D2
D3
D4
D5
D6
C
OUT
1
F
C
IN
1
F
2.7V to 5.5V
EN/SET
VIN
EN/SET
C1+
C1-
C2+
C2-
VOUT
D1
D2
D3
D4
D5
D6
GND
AAT3156
3156.2005.06.1.1
1
ChargePump
TM
Pin Descriptions
Pin Configuration
QFN44-16
(Top View)
1
2
3
4
12
11
10
9
5
6
7
8
16
15
14
13
D6
EN/SET
N/C
VOUT
C2+
C1+
C1-
C2-
GND
IN
GND
D1
AAT3156
D2
D3
D4
D5
Pin #
Symbol
Function
1
D6
Current sink input #6.
2
EN/SET
AS
2
Cwire serial interface control pin.
3
N/C
No connection.
4
VOUT
Charge pump output to drive load circuit. Requires 1F capacitor connected between
this pin and ground.
5
C2+
Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-.
6
C1+
Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-.
7
C1-
Flying capacitor 1 negative terminal.
8
C2-
Flying capacitor 2 negative terminal.
9
GND
Ground.
10
IN
Input power supply. Requires 1F capacitor connected between this pin and ground.
11
GND
Ground.
12
D1
Current sink input #1.
13
D2
Current sink input #2.
14
D3
Current sink input #3.
15
D4
Current sink input #4.
16
D5
Current sink input #5.
EP
Exposed paddle (bottom); connect to GND directly beneath package.
AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
2
3156.2005.06.1.1
Absolute Maximum Ratings
1
Thermal Information
3
Symbol
Description
Value
Units
P
D
Maximum Power Dissipation
4
2.0
W
JA
Maximum Thermal Resistance
50
C/W
Symbol
Description
Value
Units
V
IN
Input Voltage
-0.3 to 6
V
V
EN/SET
EN/SET to GND Voltage
-0.3 to V
IN
+ 0.3
V
I
OUT
2
Maximum DC Output Current
180
mA
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
3156.2005.06.1.1
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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 6.25 mW/C above 25C.
Electrical Characteristics
1
C
IN
= C
OUT
= C1 = C2 = 1.0F; T
A
= -40C to 85C, unless otherwise noted.
Typical values are at T
A
= 25C, V
IN
= 3.5V.
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,
0.3
1
No Load Current
1.5X Mode, 3.0
V
IN
5.5, Active,
1
3
mA
I
CC
Operating Current
No Load Current
2X Mode, 3.0
V
IN
5.5, Active,
2.0
3.7
No Load Current
50A Setting, 1X Mode
50
A
I
SHDN
Shutdown Current
EN/SET = 0
1
A
I
DX
I
SINK
Current Accuracy
2
I
SET
= 30mA, T
A
= 25C
27
30
33
mA
I
SET
= 4.1mA, T
A
= 25C
3.69
4.1
4.51
I
(D-Match)
Current Matching Between Any
V
F
:D1:D4 = 3.6V
0.5
%
Two Current Sink Inputs
3, 4
V
TH
1X to 1.5X or 1.5X to 2X Transition
I
SET
= 20mA
150
mV
Threshold at Any I
SINK
Pin
Charge Pump Section
T
SS
Soft-Start Time
100
s
F
CLK
Clock Frequency
1000
kHz
EN/SET
V
EN(L)
Enable Threshold Low
V
IN
= 2.7V
0.4
V
V
EN(H)
Enable Threshold High
V
IN
= 5.5V
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
EN/SET
EN/SET Input Leakage
-1
1
A
AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
4
3156.2005.06.1.1
1. The AAT3156 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. Determined by the average of all active channels.
3. Current matching is defined as the deviation of any sink current at I
OUT
= 20mA and 2mA.
4. Specification applies only to the tri-mode charge pump.
Typical Characteristics
Current Matching vs. Temperature
Temperature (
C)
Current (mA)
19.2
19.4
19.6
19.8
20.0
20.2
-40
-20
0
20
40
60
80
Channel 2
Channel 1
Channel 5
Channel 3
Channel 4
Channel 6
Turn-Off from 1.5X Mode
(V
IN
= 3.5V; 20mA Load)
100
s/div
EN
(2V/div)
I
IN
(100mA/div)
V
F
(1V/div)
Turn-On to 2X Mode
(V
IN
= 2.8V; 20mA Load)
100
s/div
EN
(2V/div)
CP
(2V/div)
I
IN
(200mA/div)
V
SINK
(500mV/div)
Turn-On to 1.5X Mode
(V
IN
= 3.8V; 20mA Load)
100
s/div
EN
(2V/div)
CP
(2V/div)
I
IN
(200mA/div)
V
SINK
(500mV/div)
Turn-On to 1X Mode
(V
IN
= 4.2V; 20mA Load)
100
s/div
EN
(2V/div)
CP
(2V/div)
I
IN
(200mA/div)
V
SINK
(500mV/div)
Efficiency vs. Supply Voltage
Supply Voltage (V)
Efficiency (%)
50
60
70
80
90
100
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.1mA
V
F
= 2.9V
20mA
V
F
= 3.4V
10.2mA
V
F
= 3.1V
AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
3156.2005.06.1.1
5
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