Circuit Operation Theory - BenQ XL2411T Product Service Manual

5.6. Circuit Operation Theory

Block diagram
The XL2411T consists of a LCD module with LED BLU (1 light bar), a power board
(with driver board), a control board (ADC key), and an Ear Jack board. The block diagram is
shown as below.
A-1) Interface board diagram:
(a) Circuit operation theory:
A basic operation theory for this interface board is to convert analog signals of Red, Green
and Blue to digital signals of Red, Green and Blue. The scaling IC has internal A/D
converter, internal OSD, built in RSDS transmitter and auto-detect input timing functions.
A/D converter is convert analog signal to digital data. OSD is offering adjustable functions to
end-user. Detect timing is for detect change mode. RSDS transmitter is used to compress
the digital RGB data, the Hsync, Vsync and pixel clock generated by Scaling then output to
LCD module. Flash-ROM stores source code and MCU (embedded in Scalar) offers H/W
DDC2Bi function & controls system processing. EEPROM is stored DDC data, OSD
common data and user mode data.
(b) IC introduction:
1. DDC (Display Data Channel) function: We use DDC IC to support DDC2Bi function.
DDC data is store in 24C02 (EEPROM). Those data related to LCD monitor specification.
PC can read them by "SDA" and "SCL" serial communication for I²C communication for
DDC2Bi.
2. Scalar IC: There are A/D, TMDS receiver, Scaling, OSD and LVDS transmitter functions
built-in two MST8556T ICs. Scaling IC is revolutionary scaling and color engine, capable
of expanding any source resolution to a highly uniform and sharp image or down scaling
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