Proper techniques to include PCB test point for SDCARD signals

Hi there,

I was wondering if I could get some advice on how to properly implement test points for probing SDCARD signals.

Since the SDCARD signals are high speed signals that requires 50 ohm controlled impedance traces, I was wondering that wouldn’t the test points have to be specific as well (to not introduce any impedance mismatch)?

How can I go about designing a PCB test point that matches the 50 ohm trace impedance? I don’t think any random test points (like a 0201 pad/ 0402 pad/ circle pad) would be able to achieve this?


If you put a 0402 pad inline with the trace, how much does it really affect the impedance of the trace?

Hi Snarky,

Did a quick calculation.

I am assuming 6.25 mils trace width for 50 ohm impedance (based on stackup). For a 0201 pad, I could use the long side to place it inline with the trace. The width of the 0201 pad comes up to 11 mils.

Doing a rough calculation yields around 20 ohms difference in Zo between the trace and the pad.

Wonder does NVIDIA have any recommendation on how to implement test points for high speed signals?


Hi, there are some resistors inline with the trace, and also some ESD components to signal lines, you can take them as reference to do design test points if necessary, or you can probe the signals on the pins of those resistors too.