Understanding the Difference between LVDS and TTL interfaces on TFT Displays

TFT displays are currently found in a variety of items, including TVs, laptops, appliances, handheld instruments, and other devices. The addition of thin film transistors to LCD architecture dramatically increased the use of LCDs across all market categories. Each transistor in the liquid crystal displays (LCD) thin-film transistor (TFT) technology serves as a pixel (that is, for each of the tiny elements that control the illumination of your display). Since every pixel has a transistor, the current required to turn on and off the pixel lighting can be minimized. There are two common types of interfaces on TFT displays, LVDS and TTL.

When the display panel was initially introduced, the traditional digital interface, TTL, became the standard of choice. The bandwidth requirements were 300Mbit/s, the resolution was VGA in 6-bit color, and the panel size was smaller than 10 inches. TTL integrated circuits represent small-scale to large-scale integration, with each chip housing up to a few hundred transistors. Compared to analog designs, TTL represented a low-cost IC that made it possible to use commercially viable digital techniques.

A transmission standard called low voltage differential signaling, or LVDS, uses differential signaling to transfer display data. Because fewer connections are required to interact with the display, these interfaces have advantages, including flexible panels, high-definition graphics, and rapid frame rates. The LVDS standard is typically linked with low system costs and dependability. Since LVDS requires less power to operate, has a relatively straightforward design, and is in high demand. The differential data transmission technique used in LVDS is more resilient to common-mode noise than single-ended systems. The advantage of the differential technique is that the receiver efficiently rejects noise that is connected to the two wires as common-mode noise, as it only takes into account the difference between the two signals (the noise appears on both lines equally). The noise is effectively reduced or eliminated.

A “0” or a “1” is represented by the voltage difference between the two wires in LVDS, which employs two wires. TTL, in contrast, employs a voltage with respect to a ground to denote a “1” or a “0,” respectively. Depending on the supply the transistor utilizes, TTL operates at a specific voltage level. This has gradually been standardized at five volts or so. In contrast to the approximately 350mV used by LVDS, this is far higher. A major difference between TTL and LVDS is that the latter uses a lot less power.

The inherent immunity to the interference of LVDS is another benefit. One significant reason is the utilization of twisted pairs, which results in a close electromagnetic field coupling. The wires will encounter the identical voltage spikes regardless. Hence the differential voltage will not change. When using TTL, a voltage spike during transmission of a “0” could mistakenly produce a “1” at the receiver.

In summary, LVDS consumes less power on TFT displays, can support a higher transmission distance, and uses a serial mode of transmission requiring fewer wires. If you are interested in using the LVDS standard on a TFT display in your next interface, visit FocusLCDs to learn more about our display technology offerings.