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TFP401A-Q1: HDMI clock - Radiated EMI issue

Martin Vit
Prodigy 145 points
Part Number: TFP401A-Q1

Hello,

We are using TI's parts TFP401AIPZPRQ1,  SN65LVDS93ADGG, TPD12S521DB, TS3DV421DGVR to build HDMI to LVDS display interface.

We don't past EMI Radiation validate test. See result in the folowing table. We identified, that HDMI clock are source for EMI radiated emission. HDMI clock is runing on cca 142 MHz. In spectrum are visible also harmonics frequency of these clocks. I did measurement of these clock, see osciloscope. Where is also visible spectrum for these clocks.

Do You have any advice how we can improve our design to past EMI test. ?

Many thanks

Best Regards Martin

Layout

  • 0
    TI__Guru**** 177141 points

    Martin

    It looks like you have common mode choke between the HDMI connector the TPD12S521DB, have you tried to change the choke and see if it helps?

    Does the HDMI gets routed with solid ground reference underneath them? I see that the HDMI signal gets routed from one layer to the other layer, do you have ground via next to the signal via?

    If you measure the clock+ and clock- with single end probe, how much skew are you seeing between them? 

    Thanks

    David