BMW 7 Series: LVDS Technology
The transmission of picture data from the CCC to the CID was performed by means of an 8-wire LVDS (low voltage differential signaling) line. With the introduction of the Car Information Computer, the video signal is now transmitted through a 2-wire LVDS line.
The change in picture data transmission in the vehicle reflect the changes made in PC technology. While the printer was formerly connected to the PC via a parallel cable, data transmission now takes place using serial USB technology.
In the following graphics, 8-wire LVDS technology is compared to the new 2-wire LVDS technology:
8-wire LVDS
Transmission of video signals via 8-wire LVDS technology with CCC and CID.
(LVDS+ and LVDS- for each of the four signal lines and an additional synchronization line)
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Fig. 85: Identifying 8-Wire LVDS
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Fig. 86: Identifying 2-Wire LVDS
2-wire LVDS
Transmission of video signals via 2-wire LVDS technology with CIC and CID.
Signal transmission through this 2-wire LVDS line offers four distinct advantages:
- Higher data transfer rate
- Simplified wiring
- Runtime differences between the individual lines are avoided
- Serial 2-wire LVDS data transmission is now much more cost-effective than 8-wire LVDS technology
The main advantage of using serial 2-wire LVDS is the resulting high picture resolution
A 4-core, shielded cable is used for the 2-wire LVDS technology. The cable consists of the four cores, LVDS+, LVDS-, 2x ground and shielding.
For Electromagnetic compatibility (EMC) reasons, the unused wire is also connected to ground.
In the illustration to the right, the advantages of both cores connected to ground are shown with the aid of field lines.
The capacitive interference of the signals is deflected to ground. The wires connected to ground form a defined potential and cannot act as antennas.
This ensures that additional interference is avoided.
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Fig. 87: Graphical Illustration Of EMC Protection Using 2-Wire LVDS
Technology
INDEX REFERENCE CHART
- Two signal-carrying cores, two cores connected to ground
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