power basics
regulate
- LDO: simple step-down; wastes (Vin−Vout)×I as heat
- Buck: efficient step-down; follow datasheet for inductor/diode/caps layout
- Protection: input diode/fuse, reverse protection, TVS for spikes
decouple everything
- 0.1 µF ceramic at each IC’s power pins
- 10–47 µF bulk per rail area
- class-II MLCCs (X7R/X5R) lose C with DC bias → add headroom
budget
sum worst-case currents; add 30–50% headroom. Check USB limits (500 mA on 2.0, 900 mA on 3.0 without negotiation).
fact
ground plane (pour) = wide, low-impedance return — helps noise & stability. caution
don’t run motors/LED strips off logic rails; give them their own supply and ground back at the source.