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ADC internal phase voltage channel gives 9 Volt once the battery voltage goes just beyond 18 Volt

Question asked by PRATIBHA SURABHI on Aug 8, 2017
Latest reply on Aug 9, 2017 by Daniel Martynek


I am implementing sensorless BEMF algorithm for BLDC motor.

I have used ADC internal channel for phase voltage.

When battery voltage is less than 18 Volt,channel shows minimum phase voltage but as we increase battery voltage beyond 18 Volts channel shows (battery voltage/2) as a phase voltage.


eg. If battery voltage is 17.9V then channel gives 300mV as a minimum phase voltage,

but If battery voltage is 18.2V then channel gives 9.1V as a phase voltage


Please tell is this behaviour is proper? If so what is the reason for this behaviour.