DVI TMDS Transmitter Chips on Graphics Cards

This article examines the active silicon chips used to generate and transmit Transition-Minimized Differential Signaling (TMDS) for DVI connections on graphics cards. It covers the historical discrete transmitter chips produced by pioneer semiconductor manufacturers, the shift toward on-die GPU integration, and the modern active level-shifter ICs utilized in DisplayPort-to-DVI signal routing.

Discrete TMDS Transmitters

Before graphics processing units (GPUs) integrated display interfaces directly onto the primary silicon die, graphics cards relied on external, dedicated transmitter integrated circuits (ICs) to convert parallel digital video data from the GPU into serialized high-speed TMDS differential pairs.

  • Silicon Image (PanelLink Series): Silicon Image co-created the DVI specification and was the dominant supplier of external TMDS transmitters.
    • SiI 164: A single-link transmitter operating up to 165 MHz, capable of driving standard resolutions up to 1920×1200 at 60 Hz. Widely used on early NVIDIA GeForce, ATI Radeon, and Matrox graphics cards.
    • SiI 1164 / SiI 160: Low-power variations tailored for mobile graphics and workstation add-in boards.
    • SiI 170 / SiI 1170: Dual-link implementations utilized to achieve bandwidth beyond 165 MHz, enabling resolutions such as 2560×1600.
  • Texas Instruments (PanelBus Series):
    • TFP410: A DVI 1.0-compliant 165 MHz transmitter that accepted a 24-bit or 12-bit dual-edge clocked parallel digital input and generated high-speed TMDS serial lines. It was a common alternative to Silicon Image parts on professional and desktop cards.
    • TFP510: An enhanced version supporting higher clock stability and dual-pixel interfaces.
  • Chrontel:
    • CH7301: A transmitter IC widely deployed on OEM systems and low-profile cards. It integrated DVI 1.0 TMDS output capability alongside analog TV-out or secondary CRT outputs.

Integrated GPU TMDS Transmitters

By the mid-2000s, graphics hardware manufacturers began moving TMDS serializers directly into the main processor package:

  • ATI/AMD: Integrated internal TMDS transmitters starting with the Radeon 9000 (RV250) and Radeon 9600 (RV350) series for single-link DVI, though external chips (such as the SiI 164) were often retained alongside the GPU to supply a second digital output or establish dual-link functionality until the Radeon X1000 and HD 2000 series fully integrated dual dual-link controllers.
  • NVIDIA: Transitioned with the GeForce FX (NV30/NV35) and GeForce 6 (NV40) generations, initially integrating one TMDS encoder on the GPU core, later embedding dual native encoders to drive dual-link DVI natively without external silicon.

Active Level Shifters and Retimers

As native DVI output was phased out in favor of DisplayPort, graphics cards supporting DVI-D output often utilize active level-shifting transceiver chips. These active ICs translate the low-voltage, AC-coupled differential signals generated by the GPU's DisplayPort dual-mode (DP++) physical layer into the DC-coupled 3.3V TMDS signaling required by the DVI specification:

  • Parade Technologies: Produces transmitters such as the PS171, PS8121, and PS8402, which function as active TMDS level shifters and jitter-reducing retimers.
  • NXP Semiconductors: Supplies ICs like the PTN3360 and PTN3381 families, standard high-speed level shifters capable of conditioning and converting video streams to DVI/HDMI TMDS signal levels.
  • Texas Instruments: Manufactures the SN75DP119 and SN75DP139 series, designed to interface embedded GPU display controllers with standard DVI output ports while ensuring TMDS clock and data integrity.