ViewSonic VX924 Service Manual page 27

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.
6.1 MB BOARD
The MB board is a two-layer, single-grounded design with ground and internal planes provided. DC power from
the power board enters the board through a 6P 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.
6.1.1 Flat panel controller: RTD2523(U7)
The heart of the system board is the Realtek RTD2523. The RTD2523 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 24.576 MHz crystal is recommended.
b) Analog to Digital Converter:
The RTD2523 chip has three ADCs (analog-to-digital converters), one for each color (red, green and blue).
The analog RGB signals are connected to RTD2523 as described below.
Pin Name
Red +
Red -
Green +
Green -
Blue +
Blue -
c) OSD: The RTD2523 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.
ViewSonic Corporation
Pin Number
37
38
34
35
30
31
24
Confidential - Do Not Copy
VX924