Standard DVI Receiver Input Impedance

This article explains the standard input impedance specifications for a Digital Visual Interface (DVI) receiver on a display. It covers the underlying signaling technology, details both the single-ended and differential impedance values required by the standard, and explains how the receiver's internal termination network maintains signal integrity across high-speed digital video links.

A standard DVI receiver has a nominal differential input impedance of 100 ohms (\(\Omega\)) and a nominal single-ended input impedance of 50 ohms (\(\Omega\)) per line.

DVI relies on Transition Minimized Differential Signaling (TMDS) to transmit digital video data. TMDS uses current-mode drivers at the transmitter (source) and requires resistive pull-up termination at the receiver (sink, such as a monitor or television).

Inside the DVI receiver, each differential pair consists of two complementary lines (positive and negative, or "true" and "complement"). The receiver terminates each individual line with a 50-ohm resistor connected to a high-level reference voltage, typically designated as \(AV_{cc}\) (+3.3 V). Because the two 50-ohm pull-up paths appear in series across the balanced differential line pair from an AC perspective, they form a combined 100-ohm differential termination.

The standard TMDS electrical specification permits a tolerance of \(\pm 10\%\) to \(\pm 15\%\) on these values, meaning the differential impedance typically falls within the 85-ohm to 115-ohm range in real-world implementations.

Matching this 100-ohm differential impedance to the characteristic impedance of standard DVI copper cabling (also designed to 100 ohms differential) is essential. Proper impedance matching prevents signal reflections, minimizes jitter, and ensures clean eye diagrams at the high pixel-clock frequencies required to transmit high-resolution video.