12V motor controller + 20V sensor
Most of microcontrollers I worked with uses voltages from 1.2V ~ 5V. I had to work with external voltage converters and conditioning circuits for components I needed interfacing with. I believe there are MCUs with higher operating voltages, but I doubt they'll be economical for general use.

I don't know how accurate you need to be with the sensor output, but IMO, there are a lot of circuits and ICs that can make it simpler to interface the sensor with the MCU already. Perhaps get an MCU with better ADC or use an opamp.