# MCP23017 Expansion HAT logic voltage

Does anyone know the voltage range for the MCP23017 HAT - 32 channel I/O Expansion HAT's logic pins to register a HIGH signal? I know the supply voltage range is from 1.8V-5.5V, but I'm assuming it's different for the logic pins. I haven't been able to access the datasheet otherwise I'd just look at that; I've tried from several different websites and they all failed to load.

• Do you have schematics for that board? If not it will be impossible to know what circuitry there is on the board which would affect the logic input range. You must know which supply voltage the chip uses and then if there is no other circuitry between connector and IO pins then the chip datasheet will have the answer. Nov 10, 2021 at 7:19

So, $$\V_\mathrm{IH} = 0.25V_\mathrm{DD} + 0.8\$$ for A[0..2] and $$\V_\mathrm{IH} = 0.8 V_\mathrm{DD}\$$ for the other pins.