Acer AL708 AL708 Monitor Service Guide - Page 10

4. THEORY OF OPERATION This section describes the function of the LCD monitor per functional block. L7EA monitor includes MB board, audio board (option), inverter board, adapter and button board. 4.1 MB BOARD The MB board is a four-layer, single-landed design with ground and internal planes provided. DC power from the power adapter enter the board through DC jack. Other connectors on the board are for inverter, audio and button board .The VGA cable is a signal cable that contains video signal, sync signal and DDC signal from PC VGA adapter. This system board consists of 4 functional areas : flat panel controller, flash ROM , power regulator and LVDS transmitter. 4.1.1 Flat panel controller...... gm2120 (U8) The heart of the system board is Genesis gm2120. The gm2120 is a graphics processing IC for LCD monitor. It provides all key IC functions required for LCD panel. On-chip functions include a high-speed triple-ADC , PLL, high sacling engine, OSD controller and on-chip microcontroller. a) Clock Generation : Crystal Input Clock (TCLK and XTAL). This is the input pair to an internal crystal oscillator and corresponding logic. A 14.318 MHz crystal is recommended. b) Hardware Reset ( Pin 5 ) Hardware Reset signal is generated by MAX6326 (U10).It assert a reset signal at least 100 ms. c) Analog to Digital Converter The gm2120 chip has three ADC's (analog-to-digital converters), one for each color (red, green and blue) The analog RGB signals are connected to gm2120 as described below Pin Name Red + Red Green + Green Blue + Blue - Pin Number 171 170 167 166 163 162 d) OSD : The gm2120 has a fully programmable ,high-quality OSD controller.The on-chip static RAM(4096 words by 24 bits) stores the cell map and the cell definitions. e) On-Chip Microcontroller (OCM) The gm2120 on-chip microcontroller(OCM) serves as the system microcontroller.That is , it programs the gm2120 and manages other devices in the system such as the keypad, the backlight, LED, audio and non-volatile RAM.using general purpose input/output (GPIO) pins. L7EA (AL708) 4-1