SDAA251 March   2026 DS90UB948-Q1

 

  1.   1
  2.   Abstract
  3. 1Introduction
  4. 2AV MUTE Mode
    1. 2.1 AV MUTE Mode in HDCP
    2. 2.2 FPD-Link HDCP Device Family-UB and UH
  5. 3UB Device Can Incorrectly Enter AV MUTE State
  6. 4How to Prevent Entering AV MUTE Mode
    1. 4.1 Prevent Video Signals During the Blanking Interval
    2. 4.2 Fix EQ Value
    3. 4.3 How to Find EQ Value
  7. 5Summary
  8. 6References

Abstract

FPDLINK III DS90UH94x deserializers implement a mode called AV MUTE which deserializers enter when the value 0x666666 is received during the blanking period (when DE=LOW). When deserializers enter AV MUTE mode, the device mutes the output video signal and audio signal, resulting in a black screen. In very rare circumstances, DS90UB94x deserializers can inadvertently enter the AV MUTE when the SoC in the systems sends signal (0x666666) during the blanking period or when a module of the system is not designed in such a way that it causes a large amount of noise interference.

This application note analyzes the causes of devices inadvertently entering AV MUTE at both the system and chip levels and provides a comprehensive design to prevent this AV MUTE mode from occurring, thus preventing systems from experiencing a black screen due to accidental AV MUTE mode entry.