FPD-Link II was introduced in 2006 and is an improved version of FPD-Link. National Semiconductor designed it specifically for automotive infotainment and camera interface applications. FPD-Link II embeds the clock in the data signal and therefore uses only one differential pair to transmit both the clock and video data. This further reduces the size, weight, and cost of cables for infotainment and safety camera applications. For example, the 24-bit color application now uses only one twisted pair instead of the 5 twisted pair used by FPD-Link.
There are additional benefits from FPD-Link II. For example, the car makers appreciate the increased cable length even with reduced cable cost. This is because of the embedded clock feature that eliminates the timing skew between clock and data signals. This was the limiting factor to cables with separate clock and data pairs because all pairs had to be manufactured at precisely equal length to control the timing skew between the clock and data pairs. This length matching added to the cable cost.
Another benefit for FPD-Link II comes from adding DC balance to the signals. Because the signal is DC balanced the application can use AC coupling, which eliminates the ground current problem between data source and destination. This is critical in the automotive applications because of the potential for large transient currents that can damage sensitive electronic equipment.
The higher resolution applications required FPD-Link II to increase the data throughput. It started at about 1 Gbit/s data throughput on a single twisted pair which is well within the capability for LVDS technology. But for the applications that required up to 1.8 Gbit/s over a single pair, LVDS was not as reliable as necessary for the automotive applications. By changing from LVDS to CML, the newest FPD-Link II chipsets were able to reliably send high bit-rate video streams over cables longer than 10m.
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