Along w/Vendor Bob's good direction - would it not always prove 'preferable' to ... 'BUFFER the MCU's GPIO from any/all 'potential' Output stress?'Our firm ALWAYS imposes some form of 'Buffer-Driver" between the Power Stage (even the intermediate, Power (Pre-Amp) Stage) and MCU.Indeed - such results in a 'cost/size ADDER' ... Yet what is the cost of a System Failure - Travel to Repair - and the (likely) 'Loss of Reputation?'The MCU IS an intelligent device - and its "Conversion to Beast of Burden" - even when operated in 'Open Drain' - invites 'issues!' (Especially so w/the passage of time - and the (expected) increase in 'Power Switched, Transient Spikes!'