AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
3151.2005.12.1.7
1
ChargePump
TM
General Description
The AAT3151 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 AAT3151 is capable of
driving four white LEDs at a total of 120mA from a
2.7V to 5.5V input. The current sinks may be oper-
ated individually or in parallel for driving higher-cur-
rent LEDs. A low external parts count (two 1F fly-
ing capacitors and two small 1F capacitors at V
IN
and V
OUT
) makes the AAT3151 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.
The charge pump output of the AAT3151 is
equipped with built-in protection for V
OUT
. Each
current sink input has short-circuit and auto-disable
to guard against LED failure conditions. Built-in
soft-start circuitry prevents excessive inrush cur-
rent during start-up. A low-current shutdown fea-
ture disconnects the load from V
IN
and reduces
quiescent current to less than 1A.
The AAT3151 is available in a Pb-free, space-saving,
thermally-enhanced, 12-pin 3x3mm TDFN 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 Four 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 Short-Circuit
Automatic Soft Start
I
Q
<1A in Shutdown
TDFN33-12 Package
Applications
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
C1
1
F
C2
1
F
D1
D2
D3
D4
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
GND
AAT3151
Pin Descriptions
Pin Configuration
TDFN33-12
(Top View)
D4
EN/SET
C1+
1
C1-
VOUT
C2+
D3
D2
D1
GND
VIN
C2-
2
3
4
5
6
12
11
10
9
8
7
Pin #
Symbol
Function
1
D4
Current sink input #4.
2
EN/SET
AS
2
Cwire serial interface control pin.
3
C1+
Flying capacitor 1 positive terminal. Connect a 1F capacitor between C1+ and C1-.
4
C1-
Flying capacitor 1 negative terminal.
5
VOUT
Charge pump output to drive load circuit. Requires 1F capacitor connected
between this pin and ground.
6
C2+
Flying capacitor 2 positive terminal. Connect a 1F capacitor between C2+ and C2-.
7
C2-
Flying capacitor 2 negative terminal.
8
VIN
Input power supply. Requires 1F capacitor connected between this pin and
ground.
9
GND
Ground.
10
D1
Current sink input #1.
11
D2
Current sink input #2.
12
D3
Current sink input #3.
EP
Exposed paddle (bottom). Connect to GND directly beneath package.
AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
2
3151.2005.12.1.7
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
150
mA
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
3151.2005.12.1.7
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 20mW/C above 25C.
Electrical Characteristics
1
C
IN
= C
OUT
= C
1
= C
2
= 1.0F; T
A
= -40C to +85C, unless otherwise noted.
Typical values are 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
(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
IL
Enable Threshold Low
V
IN
= 2.7V
0.4
V
V
IH
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
5
500
s
T
LAT
EN/SET Latch Timeout
6
500
s
I
EN/SET
EN/SET Input Leakage
-1
1
A
AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
4
3151.2005.12.1.7
1. The AAT3151 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.
5. The EN/SET pin must remain logic low (less than V
IL
) for the duration of longer than 500s to guarantee the off timeout.
6. The EN/SET pin must remain logic high (greater than V
IH
) for the duration of longer than 500s to guarantee the latch timeout.
Typical Characteristics
Current Matching vs. Temperature
Temperature (
C)
Current (mA)
19.0
19.2
19.4
19.6
19.8
20.0
20.2
20.4
-40
-20
0
20
40
60
80
Channel 2
Channel 3
Channel 1
Channel 4
Turn-Off from 1.5X Mode
(V
IN
= 3.5V; 20mA Load)
Time (500s/div)
EN
(2V/div)
I
IN
(100mA/div)
V
F
(1V/div)
Turn-On to 2X Mode
(V
IN
= 2.8V; 20mA Load)
Time (100s/div)
EN
(2V/div)
CP
(2V/div)
I
IN
(200mA/div)
V
SINK
(500mV/div)
Turn-On to 1.5X Mode
(V
IN
= 3.5V; 20mA Load)
Time (100s/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)
Time (100s/div)
EN
(2V/div)
CP
(2V/div)
I
IN
(200mA/div)
V
SINK
(500mV/div)
Efficiency vs. Supply Voltage
Supply Voltage (V)
Efficiency (%)
0
10
20
30
40
50
60
70
80
90
100
2.6
2.8
2.9
3.1
3.2
3.4
3.6
3.7
3.9
4.0
4.2
4.1mA
V
F
= 2.9V
1mA
V
F
= 2.7V
10.2mA
V
F
= 3.1V
20mA
V
F
= 3.4V
AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
3151.2005.12.1.7
5
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