What the standard defines
For hobby boards, no single document. Each microcontroller and sensor chip has a datasheet that states its supply voltage, the input voltages it reads as low and high, the output levels it produces and the absolute maximum ratings it must not exceed. Common logic families follow published industry standards, and boards built around a given chip inherit that chip’s figures.
What it does not promise
No tolerance across levels: a 3.3 V input is not assumed to accept 5 V unless the datasheet says so. No guarantee that a 3.3 V output is read as high by a 5 V input. No current capacity: a logic pin is a signal, with its own current limits. No protection against wiring mistakes.
What it works with
Level shifters and voltage dividers that join the two levels. Bench power supplies with current limits that make first power-up forgiving. USB-C and regulators that feed a board’s supply rail.
Questions makers ask before buying
Where do I find a pin’s voltage limit?
In the board maker’s documentation and the microcontroller’s datasheet, which state the operating voltage and whether any pins tolerate more.
Do sensor modules convert levels themselves?
Some include a regulator and level shifting, which their documentation states; many do not. The module description is the place to check.
Last reviewed 15 September 2026