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HDMI high speed signal layout

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Junior Member level 1
Sep 25, 2005
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Hi all,

I have a question regarding HDMI layout:
I have a HDMI board I need to layout, this board has just two connector: one connector is to my main board, and the other is a HDMI connector(i.e. this is a HDMI adapter board).
In your professional opinion, if I don't match the lines to 100 ohms will this cause the HDMI to fail?
Consider that the distance between the connectors is about 5MM (one is on the top, the other is bottom).
I usually just take care to match the board properly, however this is just an adapter board, and I'm not sure it's worth the effort.

Has anyone had an experience with such an issue?

In my *OPINION* you will be OK, the connectors themselve introduce a degree of impedance mismatch so there is some 'slack' in the specification to accommodate them. I would still try to match the track impedances if possible but the most important factor would be the track lengths. Try to keep them all the same length if possible, HDMI is well known to have poor tolerance to different delays between signals so try to match the delays by using near identical path lengths.

Even with adaptor boards I tend to match impedances, it is not the length of the impedance mismatch that is the issue, but the change in impedance the waveform sees when travelling down the waveguide (the actual point of change from one impedance to another).
Of course if your connectors add an impedance mismatch then all bets are off......

Thanks marce, but did you actually have a problem with such a board?

What connector do you use on your board?

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