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Alaeddine , 01-21-2025, 02:58 PM

Hi, i wanted to know what's the purpose of putting additional ground vias close to the ground pins of an IC. And in this case, should i connect them to the ground pad of the decoupling cap (marked number 2)? Or is number 1 the correct one ?

Denis , 01-21-2025, 04:15 PM

I guess the decoupling capacitor is connected to the IC using 3V3 and ground pins.
Probably ground via beneath the IC.
2 ground vias connected together by a wire can cause ground loop.

Denis , 01-21-2025, 04:19 PM

Here is a similar decoupling capacitor connected to the STM.

QDrives , 01-21-2025, 08:45 PM

You place Gnd vias close to the IC pin to reduce the impedance and therefor the voltage drop as seen by the IC.
The same goes for the capacitor.
As a result, you can have multiple vias connected together on copper top.
Both 1 and 2 are ok.
Ground loops, as @Denis mentioned, are of **no** concern.

Denis , 01-21-2025, 09:24 PM

I'm referring to the lecture in the course "Mixed-Signal Hardware Design with KiCad".
Lesson 12, minute 7.

QDrives , 01-21-2025, 09:41 PM

I do not have access to the course, but as I mentioned, ground loops are of no concern.

Denis , 01-22-2025, 05:48 AM

Ok. Call Phil and ask him to update a lecture.

QDrives , 01-22-2025, 04:56 PM

Why? Is Phil not entitled to his own opinion?
Watch the video on shielding here https://youtu.be/Hj-HVve1QC4?t=2072

Alaeddine , 01-22-2025, 06:02 PM

is it the same topic for the trace in my case ?

QDrives , 01-22-2025, 07:36 PM

That comment was meant for @Denis as I assume he was referring to ground loops.

Denis , 01-22-2025, 07:50 PM

I found another video related to the question https://youtu.be/3swYweisn5g?si=0Ri8HQo-dY1OisUB
On the minute 6 was revived our case.
The conclusion is: inductance caused by a loop is way smaller than trace.
If there is any stray magnetic field present in the PCB, it would rather affect trace itself rather than 2 vias.