I am designing a 3-phase BLDC motor driver right now and have limited space on my pins left.
Although I do have current limiting (ie. comparators) on each of the three phases, I have chosen to also run those readings off to 3 ADC pins to be able to get readings of the motor phase currents (ie. the ability to measure motor currents during flyback as opposed to the battery current which would not allows this but would only require on ADC pin). Because I have chosen this route, I only have two pins left with the following functions:
Pin1- Comparator or ADC
Pin2- ADC
Now I am left with voltage and temperature. I can't decide on the importance of each- voltage limiting (ie. comparators) would provide faster response when the battery voltage gets too low to shut off everything for protection while voltage sensing (ie. ADC) would allow me to better control the motor (I already have speed measurement though so it would be used for self-calibrating control coefficients used for control system predictions).
Then I have temperature which would be nice to measure though I am not sure what I would do with the readings, but temperature limiting would be much more important though I am not sure how accurately I could measure it- I don't have enough pins for a per-phase or per-transistor temperature sensing. I just have enough pins for one. Not all the MOSFETs have their large heatsinking pins connected to ground either so I am not sure if I could effectively measure the temperature of all the FETs with just a single silicon temperature sensor connected to the ground plane.
Or should I forego measuring motor phase currents for measuring battery current and two extra pins?
What would you guys pick? I'm fairly sure temperature sensing is kind of useless, but temperature limiting could be very important. I am undecided on voltage sensing or voltage limiting, however, and am not certain that I really need to be able to measure the motor phase currents (I already have current limiting on each phase).
Although I do have current limiting (ie. comparators) on each of the three phases, I have chosen to also run those readings off to 3 ADC pins to be able to get readings of the motor phase currents (ie. the ability to measure motor currents during flyback as opposed to the battery current which would not allows this but would only require on ADC pin). Because I have chosen this route, I only have two pins left with the following functions:
Pin1- Comparator or ADC
Pin2- ADC
Now I am left with voltage and temperature. I can't decide on the importance of each- voltage limiting (ie. comparators) would provide faster response when the battery voltage gets too low to shut off everything for protection while voltage sensing (ie. ADC) would allow me to better control the motor (I already have speed measurement though so it would be used for self-calibrating control coefficients used for control system predictions).
Then I have temperature which would be nice to measure though I am not sure what I would do with the readings, but temperature limiting would be much more important though I am not sure how accurately I could measure it- I don't have enough pins for a per-phase or per-transistor temperature sensing. I just have enough pins for one. Not all the MOSFETs have their large heatsinking pins connected to ground either so I am not sure if I could effectively measure the temperature of all the FETs with just a single silicon temperature sensor connected to the ground plane.
Or should I forego measuring motor phase currents for measuring battery current and two extra pins?
What would you guys pick? I'm fairly sure temperature sensing is kind of useless, but temperature limiting could be very important. I am undecided on voltage sensing or voltage limiting, however, and am not certain that I really need to be able to measure the motor phase currents (I already have current limiting on each phase).