Tap AC-coupling for LVDS signals

Low voltage differential signaling is a physical layer data interface standard defined by the TIA/EIA-644 and the IEEE 1596.3 standards. It is designed for high-speed, low-power, and low-noise point-to-point communication, typically over balanced, controlled-impedance media of 100. Like other differential signaling standards, LVDS radiates less noise than single-ended signals due to the canceling of magnetic fields, and is more immune to noise because it is coupled onto the two wires as a common-mode signal. In addition, LVDS drivers use a current-steering output configuration which reduces ground bounce and eliminates shoot-through current compared with voltage-mode drivers used in other differential signaling standards.

Using capacitors to AC-couple an LVDS data link provides many benefits, such as level shifting, removal of common-mode errors, and protection against input-voltage fault conditions. This article by John Guy of Maxim Integrated Products will help designers select the proper capacitor and the termination topology for this design approach. Common troubleshooting issues are discussed in the article.

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