Panel display interfaces and bandwidth: From TTL, LVDS, TDMS to DisplayPort

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Figure 1: Display Interface Roadmap: Seeking Higher Bandwidth. This image shows the increase in bandwidth of displays since 1994.

Panel display interface standards
To best see the future, it's appropriate to recap the evolution of panel display interface standards. From Transistor-Transistor Logic (TTL) all the way to today's DisplayPort digital display interface, here is an overview of panel display interfaces from the early 1960s to 2007 and a bird's-eye view of what's next.

Transistor-Transistor Logic
The classic digital interface, TTL, was the choice of interface standards when the display panel was first introduced. At that time, the panel size was less than 10 inches with the resolution at VGA in 6-bit color and bandwidth requirements at 300 megabits per second (Mbps). TTL integrated circuits (ICs) represent small-scale to large-scale integration, with each chip housing up to a few hundred transistors compared with today's microprocessors at tens of millions of transistors.

TTL's popularity was based on Texas Instruments' (TI) introduction of the 7400 series of ICs. While TI's family rapidly became the standard, Motorola, Signetics, SGS-Thomson, National Semiconductor and others joined TI with their own devices. TTL represented a low-cost IC that enabled economically feasible digital techniques vs. analog solutions.

As soon as panel size grew to the 15-inch range in the latter half of the 1990s, resolution became XGA and bandwidth requirements jumped to 850Mbps. Challenges included power consumption and electromagnetic interference (EMI), making the slow TTL interface a bottleneck on the display panel.

Next: LVDS Display Interface (LDI)