Vx2025Wm - ViewSonic VX2025wm-1 Service Manual

6. THEORY OF OPERATION
This section describes the function of the LCD monitor per functional block.
This monitor includes MB board, power board, Inverter board and button board.
6.1 MB BOARD
The MB board is a two-layer, single-landed. 12V DC power from the power adapter enters the board
through connector CN6. Other connectors on the board are for audio speaker 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 Audio
amplifier
6.1.1 Flat panel controller... NT68563HF (IC2)
The heart of the system board is the scalar chip of NT68563HF. The scaler is a highly integrated flat panel
display controller that interfaces analog, digital, and video inputs. It combines a triple ADC, a DVI
compliant TMDS receiver, a multi-color on screen display (OSD) controller and many other functions in a
single chip. It provides user a simple, flexible and cost-effective solution for various flat panel display
products.
The NT68563HF operates at frequencies up to 205MHz (analog only), suitable for LCD monitor up to
UXGA resolution. The NT68563HF also build-in noise reduction function to provide more stable video
quality, spread spectrum to provide low EMI solution, sRGB for video color space convert, post pattern for
manufacture test.
a) Clock Generation:
This is the input pair to an internal crystal oscillator and corresponding logic. A 12.000 MHz crystal is
recommended.
b) Hardware Reset (Pin127):
Hardware Reset signal is provided by MCU (IC3), it is active high.
c) Analog to Digital Converter:
The NT68563HF chip has triple ADC's (analog-to-digital converters), one for each color (red, green and
blue) .The analog RGB and synchronous signals are connected to NT68563 as described below:
Pin Name
Red +
Red -
Green +
Green -
Blue +
Blue -
H sync
V sync
ViewSonic Corporation
Pin Number
25
26
23
24
20
21
39
40
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VX2025wm -1