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Crosstalk problem using TS3DV421

user3641249
Prodigy 20 points
Other Parts Discussed in Thread: TS3DV421, TS3DV642, SN65CML100, TFP401

Hello,

I'm using a TS3DV421 as an HDMI multiplexer 2:1 and there is cross talk between channels.

When channel B is selected, the cross talk is acceptable and the receiver receives information correctly.

However, when channel A is selected, the cross talk is very important and the receiver can't display image correctly.

Both sources emit simultaneously.

Could you give me a reference design or a design guide for this device ?

Regards,

C. HEBERT

  • 0
    TI__Mastermind 45380 points
    C. Herbert,

    Could you post a schematic, layout, and screen shots of the behavior in question that we can review?

    We have an evaluation module for our newer version HDMI switch the TS3DV642 you can use as a guide. This device has an updated datasheet with some application and layout guidelines. There is also a users guide to the evaluation module that could also be helpful. www.ti.com/.../ts3dv642evm

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    Prodigy 20 points

    Hello,

    Thank you for your answer. You will find in attachment a part of schematic around the ts3dv421.

    All signals come directly from connectors, except HDMI_1_CLOCK_BUF_CML which is buffered because I have a system to check the clock presence. HDMI_1_CLOCK_BUF_CML is driven by an SN65CML100(see clock.png). Outputs of ts3dv421 go directly to inputs of an TFP401.

    HDMI sources are configured to emit permanently(both HPD signals high).

    ts3dv421 is supplied between 1.5V and 3.3V. You will find in attachment the voltage rising at power up. I think the  overvoltage during power up  damages the component. What do you think about this hypothesis ?

    I think I will change the ts3dv421 for the ts3dv642 but I want to be sure solving the problem.

    Best regards,

    C. HEBERT

  • 0 in reply to user3641249
    TI__Genius 11665 points

    Hello C. Herbert,

    Thank you for the detailed description.

    Based upon the o-scope screenshot, I believe your hypothesis is correct. the TS3DV421 is at risk of damage because the Vss is being ramped too late compared to when the Vdd is ramped. Is it possible to ramp Vss sooner so that the difference between Vdd and Vss never exceeds 2.1 V?

    Vdd - Vss = 3.6 V - 1.5 V = 2.1 V 

    As far as your crosstalk problem goes, I would advise verifying that the power sequence is appropriate and Vdd -  Vss is never greater than 2.1 V. Hopefully that solves the issue, but if not, we can go from there.

    I cannot say that switching to the TS3DV642 will guarantee to solve this problem immediately, but I would still advise switching to this part based upon the information Adam provided in the previous post. The TS3DV642 is a newer part, and thus has better support material.

    Please let me know if altering the power sequencing helps resolve the issue.

    Regards,

    Jared