LG KE600 Service Manual - Page 45

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. VBAT C352 1u FLASH_EN LCD_BACKLIGHT R350 0 R362 0 R356 R357 100K 100K C346 1u C347 1u C348 1u C1+ 11 C1- 12 14 C2+ 15 C2- 2 C3+ 1 C3- 4 VIN 9 GND 17 PGND 3 VOUT_FL VOUT_BL 13 NC 8 16 EN_FLSH 10 EN_SET U306 5 ISINK1 6 ISINK2 7 ISINK3 AAT2807AIXN-4.5 C353 1u R343 62 R344 62 R346 62 R347 62 C354 1u FLASH_LED MLED MLED1 MLED2 MLED3 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 - 46 -