AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
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 1µF fly-
ing capacitors and two small 1µF capacitors at V
IN
and V
OUT
) makes the AAT3151 ideally suited for
small battery-powered applications.
AnalogicTech's AS
2
Cwire™ (Advanced Simple
Serial Control™) 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 50µA for optimized efficiency, with
a low housekeeping current of only 50µA.
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 1µA.
The AAT3151 is available in a Pb-free, space-saving,
thermally-enhanced, 12-pin 3x3mm TDFN package,
or in the lower-profile STDFN package.
Features
•
•
ChargePump
™
•
•
•
•
•
•
•
•
•
•
•
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 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 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
<1µA in Shutdown
TDFN33-12 or STDFN33-12 Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
2.7V to 5.5V
C
IN
1µF
VIN
C1+
C1
1µF
C1-
C2+
AAT3151
C2-
VOUT
C2
1µF
MAIN
SUB
D1
D2
D3
D4
C
OUT
1µF
EN/SET
EN/SET
D1
D2
D3
GND
D4
3151.2007.03.1.10
1
AAT3151
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
EP
Symbol
D4
EN/SET
C1+
C1-
VOUT
C2+
C2-
VIN
GND
D1
D2
D3
Function
Current sink input #4.
AS
2
Cwire serial interface control pin.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Flying capacitor 1 negative terminal.
Charge pump output to drive load circuit. 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.
Input power supply. Requires 1µF capacitor connected between this pin and
ground.
Ground.
Current sink input #1.
Current sink input #2.
Current sink input #3.
Exposed paddle (bottom). Connect to GND directly beneath package.
Pin Configuration
TDFN33-12/STDFN33-12
(Top View)
D4
EN/SET
C1+
C1-
VOUT
C2+
1
2
3
4
5
6
12
11
10
9
8
7
D3
D2
D1
GND
VIN
C2-
2
3151.2007.03.1.10
AAT3151
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
Description
Input Voltage
EN/SET to GND Voltage
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
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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 20mW/°C above 25°C.
3151.2007.03.1.10
3
AAT3151
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
= 3.5V.
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
EN/SET = 0
I
SET
= 30mA, T
A
= 25°C
0.3
1
2.0
50
27
30
0.5
150
1
33
Typ
Max
5.5
1
3
3.7
Units
V
Input Power Supply
V
IN
Operation Range
I
CC
Operating Current
mA
Shutdown Current
I
SINK
Current Accuracy
2
Current Matching Between Any
I
(D-Match)
V
F
:D1:D4 = 3.6V
Two Current Sink Inputs
3, 4
1X to 1.5X or 1.5X to 2X Transition
V
TH
I
SET
= 20mA
Threshold at Any I
SINK
Pin
Charge Pump Section
T
SS
Soft-Start Time
F
CLK
Clock Frequency
EN/SET
V
IL
Enable Threshold Low
V
IN
= 2.7V
V
IH
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
5
T
LAT
EN/SET Latch Timeout
6
I
EN/SET
EN/SET Input Leakage
I
SHDN
I
DX
µA
µA
mA
%
mV
100
1000
0.4
1.4
0.3
50
75
500
500
1
75
µs
kHz
V
V
µs
ns
µs
µs
µs
µA
-1
1. The AAT3151 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. 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 500µs to guarantee the off timeout.
6. The EN/SET pin must remain logic high (greater than V
IH
) for the duration of longer than 500µs to guarantee the latch timeout.
4
3151.2007.03.1.10
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