Other Parts Discussed in Thread: MOTORWARE
I have drv8303 motor control chip with 3 sense resistors, on in each phase leg (between lower mosfet source pin and DC-). drv8303 only allows 2 current sense so the third shunt resistor current sense is processed externally via an opamp such that DSP receives current feedback from all three phases. normally in an AC motor drive the mosfet will see both Drain to Source and Source to Drain current so the sense resistor and drv8303 and/or op-amp has to allow for bi-directional (unipolar with a reference voltage such that 1.65V is zero amps) in a standard way. all relatively normal. not my question.. let's say i ONLY sampled the shunt resistor's sensed voltage when the lower mosfet passed current ONLY in Drain to Source direction. sure the sense resistor and the drv8303/op-amp will see bi-directional.. but for argument sakes lets say that DSP purposely ignores all sampled data when current was flowing Source to Drain (shunt resistor was "negative" voltage). would the Instaspin FOC still work? could it be made to work with some code change?
