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Original question:

TMDS181: HDMI 4k video in source mode setup

TMDS181: Could not output 4K/60Hz

Gabriel Wang1
Genius 4995 points

Part Number: TMDS181

Dear Expert

We set the IIC bus low , and set the PIN22 VSadj  pin connected a 7.06kohm resistense to GND .

And we found It can output 4K30HZ, but it cannot output when it is greater than 30HZ. Do the configuration parameters need to be adjusted.

Below is sch,could u help check the sch ,and do we need set the EQ ?

  • 0
    TI__Guru**** 189451 points

    Hi,

    With I2C bus being low, you are in pin strap mode. TMDS181 will then automatically configure itself base on the snooping of the DDC bus. The EQ should be set to NC so TMDS181 RX EQ will automatically adapt.

    Can you please read TMDS181 register 0x0B? Bit 1 is TMDS_CLOCK_RATIO_STATUS. This bit is automatically updated from snoop of DDC bus. For HDMI1.4, it will be 0. For HDMI2.0, it will be 1. For 4k@60Hz, if you do not see this bit being automatically set to 1, then we need to look at the DDC bus to make sure the source is correctly write to the slave SCDC register address 0xA8 offset 0x20 bit 1.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Genius 4995 points

    Hi David

    Hello, I am designing based on the schematic diagram of MianLianKe, with the DDC bus SRC terminal connected to ground. Could you please help confirm how to connect it.

  • 0 in reply to Gabriel Wang1
    TI__Guru**** 189451 points

    Hi,

    Please see below implementation.

    Thanks

    David