Saturday, 24 September 2016

arduino - How to 'de-mux' a tri-state pin?


I would like to use a single pin (tri-state buffer, 3.3V logic in case this matters) to drive two P-channel MOSFETs as high-side switches. Only one of them will be 'on' at any time. When the pin is in the high-impedance state (hi-Z), I would like both turned off.


The solution I came up with is to pull-up the hi-Z state (to 0.2*Vcc, see comments) and use two comparators (open collector type) to drive the FETs when the pin is in either the Lo or High state:


schematic


simulate this circuit – Schematic created using CircuitLab


I wonder: is there a better, easier or more elegant approach to this? Is this solution suitable for fast switching?




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