High Efficiency White LED Drivers
for Backlight and Keypad
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
EP
AAT1236
Symbol
VIN
OV
EN
B1
B2
RSET
IN
GND
SW
SDA
SCL
AGND
A3
A2
A1
LIN
Function
Input supply for the converter. Connect a 2.2µF or larger ceramic capacitor from VIN to GND.
Boost output over voltage detect pin. Use resistor divider to set the circuit's external over-
voltage protection. See Applications Information for details.
Enable pin.
Backlight current sink 1. Connect the cathode of the last LED in the string to B1.
Backlight current sink 2. Connect the cathode of the last LED in the string to B2.
LED current set resistor. A 22.6kΩ resistor from RSET to AGND sets the maximum LED cur-
rent in A1-A3 and B1-B2 to 20mA.
Input bias supply for the internal circuitry. Connect IN to VIN directly at the AAT1236.
Power ground for the boost converter. Connect GND to AGND at a single point as close to
the AAT1236 as practical.
Boost converter switching node. A 2.2µH inductor, connected between SW and LIN, sets the
boost converter's switching frequency.
I
2
C interface serial data line.
I
2
C interface serial clock line.
Ground pin. Connect AGND to GND at a single point as close to the AAT1236 as practical.
Auxiliary current sink 3. Connect the cathode of the last LED in the string to A3.
Auxiliary current sink 2. Connect the cathode of the last LED in the string to A2.
Auxiliary current sink 1. Connect the cathode of the last LED in the string to A1.
Switched power input. Connect LIN to the external power inductor.
Exposed paddle (bottom). Connected internally to SW. Connect to SW or leave floating.
Pin Configuration
TDFN34-16
(Top View)
VIN
OV
EN
B1
B2
RSET
IN
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LIN
A1
A2
A3
AGND
SCL
SDA
SW
2
1236.2007.02.1.1
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
