ViewSonic VP2330WB Service Manual - Page 28

6. THEORY OF OPERATION This section describes the function of the LCD monitor per functional block. This monitor includes MB board, power board and button board and USB board 6.1 MB BOARD The MB board is a Four-layer, single-landed design with ground and internal planes provided. DC power from the power board enters the board through a 8P connector. The other connector on the board is for the button board. The VGA cable is a signal cable that carries the video, sync and DDC signals from the PC VGA adapter. This system board consists of 4 functional areas: flat panel controller, MCU with flash ROM, and power regulators USB function. . 6.1.1 Flat panel controller... Gm1601H(U21) The heart of the system board is the Realtek Gm1601H. The Gm1601H is a graphics processing IC designed for LCD monitors. It provides all key IC functions required for LCD displays. On-chip functions include a high-speed triple-ADC, PLL, high scaling engine and OSD controller. 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) Analog to Digital Converter: The Gm1601H chip has three ADC's (analog-to-digital converters), one for each color (red, green and blue) .The analog RGB signals are connected to Gm1601H as described below Pin Name Pin Number Red + D2 Red - D1 Green + C2 Green - C1 Blue + B2 Blue - B1 c) SST 39VF040 Micro Controller: The SST 39VF040 micro controller (MCU) serves as the system micro controller. It programs the Gm1601H and manages other devices in the system such as the keypad Pin number Pin Number Usage AE24 Key / Power on ,off P3 NV_RAM (U4) SDA P4 NV_RAM (U4) SCL AF24 Key_down AF26 Key_right AF25 Key_up AE25 Key_left AD24 Key_select D25 LED_red D26 LED_green AC2 LCD panel power1 on / off control C25 Backlight on / off control ViewSonic Corporation Confidential - Do Not Copy 25 VP2330wb