ViewSonic VA2012w-2 Service Manual page 25

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
d) Internal OSD: Internal SRAM allows up to 2048 characters, with programmable OSD frame size. Width is 64 columns,
and Height is 32 row.
ViewSonic Corporation
Pin Number
25
26
23
24
20
21
39
40
22
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