PCB Layout question

C

CoreyCoop

Active member
I am in the process of laying out a PCB which will have a Teensy 4.1 on it. My question is should I, or should I not, connect to all the GND pins? On my PCB there will be a ground plane, so I would think it would be a good idea, and not create ground loops. Maybe I'm wrong?

Taking this a step further, when using any of the Teensys on hand soldered proto-boards, which I do a fair amount, my question is the same; is it a good or bad idea to connect the GND in multiple places on the Teensys? I have always kept it to one GND connection, but is that correct procedure?

C.
 
Rule number one - always connect the ground pins. They are there to be connected. They aren't big enough to cause ground loops and there are worse consequences for not connecting them usually. Watch out for different digital and analogue grounds in other situations.
 
You effectively have two parallel boards with ground planes, so this is like stitching groundplanes together, connect at as many
points as possible to allow ground-return paths for signals to route themselves as close to the signal as possible.

An ideal routing would use one ground pin per two signals, so that every signal has a neighbour ground. A pertinent example
might be the RPi Pico board which has a ground pin every 4 signals or so (note this board has a lot of pins so can afford this).
The pressure to have lots of GPIO in a small form factor works against good layout rules...

As said above digital grounding is very different from low-speed analog grounding which uses star-topology, for fast
logic we are talking Maxwell's equations, not Kirchoff's laws, or put another way stray inductance is dominant.

For high speed signals anytime you force a ground return current away from a signal you form a loop antenna to
broadcast and pick up EMI.
 
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