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SN65DP159: Random Screen Blackouts in IDLE State

Tom Tsao
Expert 1850 points
Part Number: SN65DP159

Tool/software:

Dear TI Support Team,

We are using the SN65DP159RSB in our design and have encountered an issue. When the system is in an IDLE state, the HDMI display randomly goes dark, behaving somewhat like a screen entering sleep mode.

Could you please advise on the possible causes of this behavior and any recommended steps to troubleshoot or resolve the issue?

Thank you for your assistance.

  • 0
    TI__Guru**** 176561 points

    Hi,

    Can you please share your schematic for review?

    If you probe the DP159 TMDS input and output such as the IN_CLKP/N and OUT_CLKP/N, are you seeing a valid clock during IDLE state?

    If you look at the DP159 mode of operation as shown below, the DP159 will only enter into power down mode if HPD_SNK is L, OE is L, or a '1' is being written to register 0x09 bit 3.

    Thanks
    David

  • 0 in reply to David (ASIC) Liu
    Expert 1850 points

    Hi David

    Thank you for your assistance. I have measured the signals, and during the abnormal condition, both the input and output signals show no changes, no jitter, and no disconnections. The HPD signal has also not been cut off.
    May I ask, in my circuit, what impact would it have if the P/N signals were swapped?

  • 0 in reply to Tom Tsao
    TI__Guru**** 176561 points

    Hi,

    The SNx5DP159 can change the polarity of the input signals by using Register 0x9h bit 6 to swap polarity in the I2C Mode. But polarity swap only works for retimer mode. If set and data rate falls below 1.0-Gbps in this mode the polarity function will be lost. So I wonder when in the IDLE state, the data rate falls below 1Gbps, you lose the polarity function, and then see the blank state.

    Thanks

    David