Lesson · Problem 5
Build a Minimal MCU Board
Each supply pin gets its own nearby capacitor, on the same supply and the same ground.
Try it
Copper is the shared 3.3 V rail. Blue is the shared ground. Each capacitor is a shunt from its supply pin to that ground. Reset, boot, and the debug pins are on the card. This drawing is only the supply.
VDD1, VDD2, and VDDA each have a 100 nF on a short path to ground. The capacitors still join the same 3.3 V rail and the same ground. A short path is not a separate supply.
Why it works
VDD1, VDD2, and VDDA each feed a different part of the chip, so each one gets its own 100 nF on a short path. Those capacitors still join the same 3.3 V rail and the same ground. A short path is not a separate power supply.
Key takeaway
Each supply pin gets its own nearby capacitor. Those capacitors still share one 3.3 V rail and one ground.
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