Linear regulator dissipation
✕ errorthermal/regulator-dissipation
What it looks like
REG2 dissipates ~2.4 W at the connected load (dropping 12→3.3 V at 280 mA — that needs a heatsink or a switcher, not hope).
What it checks
For a linear regulator, heat is (Vin − Vout) × Iout — computed from the actual connected input rail and actual load, not the datasheet's worst case.
Why it matters
Linear regulators turn every dropped volt into heat at full load current. A TO-220 with no heatsink handles a watt or two; an SOT-23 far less. Past that it hits thermal shutdown and your rail cycles on and off — which looks exactly like a software bug.
How to fix it
Switch to a buck converter for big drops (it converts instead of burning), reduce the input-output differential (pre-regulate), or add real copper/heatsink area sized for the computed watts.
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