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DRV8305: Question for DRV8305

Part Number: DRV8305

Hi Team,

The customer would like to know is DRV8305 able to reconstruct the bus current through three-phase low-side resistance sampling?

Thanks,

Annie

  • Hello Annie,

    Thanks for posting on the Motor Driver forums! I'll definitely need to talk to the team about what we can offer for suggestions. Expect a longer resolution time for this question, I'll try my best to give you an update 9/18/20 CDT.

    This depends on commutation type, other sources that use bus current (regulator currents, charge pump current, current sense amp consumption, etc), and . Take a look at the effort needed to theoretically understand a stepper motor: https://ieeexplore.ieee.org/document/6073479  (Note: this isn't completely applicable for the three phase brushless DC motor, but close enough to give you some insight).

    Sensing the 3 phase currents from the SOx outputs will definitely help in the calculation. Based on the math, it might be more effective to sense the bus current directly than using a more powerful processor that can calculate, and the reconstruct the bus current in real time.

    If you can help us understand the application knowing the bus current, that could help us answer the question more accurately.

    Best,

    -Cole

  • Hello Annie,

    Talking with the team, this is more of a research project if we take the theoretical approach. Otherwise, its much better to conduct an experiment to measure bus current and the low side currents and plot the relationship to see if a trend line can be extracted for your system. The equation or relationship can then be reconstructed if the low-sides are measured using the SOx pins. 

    As such, you have have questions regarding the SOx pins, let us know. Otherwise, the reconstruction equation will be dependent on your system and under your control. Apologizes for the lack of a theoretical answer. 

    Best,

    -Cole