Low-voltage differential signaling

Low-voltage differential signaling, or LVDS, also known as TIA/EIA-644, is a technical standard that specifies electrical characteristics of a differential, serial communications protocol. LVDS operates at low power and can run at very high speeds using inexpensive twisted-pair copper cables. Since LVDS is a physical layer specification only, many data communication standards and applications use it but then add a data link layer as defined in the OSI model on top of it.

LVDS was introduced in 1994, and has become popular in products such as LCD-TVs, automotive infotainment systems, industrial cameras and machine vision, notebook and tablet computers, and communications systems. The typical applications are high-speed video, graphics, video camera data transfers, and general purpose computer buses. Early on, the notebook and LCD display vendors commonly used the term LVDS instead of FPD-Link when referring to their application, and the term LVDS has mistakenly become synonymous with Flat Panel Display Link in the video-display engineering vocabulary.

Differential signaling

Differential signaling is a method for electrically transmitting information using two complementary signals. The technique sends the same electrical signal as a differential pair of signals, each in its own conductor. The pair of conductors can be wires (typically twisted together) or traces on a circuit board. The receiving circuit responds to the electrical difference between the two signals, rather than the difference between a single wire and ground. The opposite technique is called single-ended signaling. Differential pairs are usually found on printed circuit boards, in twisted-pair and ribbon cables, and in connectors.

Advantages

Provided that the source- and receiver impedances in the differential signalling circuit are equal, external electromagnetic interference tends to affect both conductors identically. Since the receiving circuit only detects the difference between the wires, the technique resists electromagnetic noise compared to one conductor with an un-paired reference (ground). The technique works for both analog signaling, as in balanced audio—and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express, DisplayPort, HDMI, and USB.