Lcd Back Light Illumination - LG KE600 - Cell Phone Service Manual

3. TECHNICAL BRIEF

3.10. LCD back light illumination

Employed the AAT2807 is a dual charge pump designed to support both the white LED backlight and
flash applications for systems operating with lithium-ion/polymer batteries. The backlight charge pump
is capable of driving up to three LEDs at a total of 60mA. The current sinks may be operated
individually or in parallel for driving higher current LEDs. To maximize power efficiency, the charge
pump operates in 1X, 1.5X, or 2X mode, where the mode of operation is automatically selected by
comparing the forward voltage of each LED with the input voltage.
R350
FLASH_EN
R362
LCD_BACKLIGHT
Figure 18 LCD Back light unit and Flash LED charge pump IC
The interface relies on the number of rising edges of the EN/SET pin to address and load the registers.
S2Cwire latches data or address after the EN/SET pin has been held high for time TLAT. The interface
records rising edges of the EN/SET pin and decodes them into 16 different states, as indicated in table
VBAT
4
VIN
C352
1u
9
GND
17
PGND
0 16
EN_FLSH
0
10
EN_SET
U306
R356 R357
100K 100K
C346
C347 C348
1u
1u 1u
3
VOUT_FL
13
VOUT_BL
C353
1u
8
NC
5
ISINK1
6
ISINK2
7
ISINK3
AAT2807AIXN-4.5
- 46 -
R343 62
R344 62
R346 62
R347 62
FLASH_LED
MLED
MLED1
MLED2
MLED3
C354
1u