fine-pitch ribbon cable TDR impedance

Dec 02, 2025 Last reply: 7 months ago 1 Replies

The usual 3M stuff (50 mil wire pitch) measures about 110 ohms, running gnd-sig-gnd.



But the 25 mil pitch cable measures 75 ohms!



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That's a lot nicer to mate up with a PCB.


John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics


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The FPGA only allows a few choices of drive strength, so it's best to go low on the source termination and let the gate input overshoot.

I could go even lower. The Efinix T20 gives 4 choices of drive strength and two speeds.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

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