Placement matters: what happen when a decoupling capacitor being placed far far away from the IC that it is supposed to decouple? Compare diagram below to those in previous posts:
This time, I have removed all traces that that is not related to positive supply decouling capacitor discharge path. Obviously in this placement, the decoupling capacitor discharge path is much longer that those in posts stated above. In this case there are much larger series inductance that discourage good decoupling performance (as it is more troublesome for capacitor to discharge).
Top view of top signals – positive supply decoupling capacitor discharge path