DRV8316REVM: How to use active demagnetization on DRV8316REVM

Hello Kenji-san, and thanks for your question!

1. First, what is the difference in automatic synchronous rectification (ASR) mode and automatic asynchronous rectification (AAR) mode?

   1. ASR - The device automatically turns ON any MOSFET where the body diode is conducting in order to minimize diode losses.
      1. ASR applies during commutation when the phase is put into Hi-Z - the MOSFET is turned ON rather than using body diode conduction in order to reduce the power dissipation
         1. 
      2. ASR also applies during PWM. If current is flowing through a body diode, the device will automatically turn ON that MOSFET to minimize power dissipation.
         1. 
   2. AAR - The device automatically turns OFF the low-side MOSFET when the current is low and decreasing in order to prevent current from starting to flow in the reverse direction.
      1. 

1. In what case use, and change the settings of EN_ASR and EN_AAR?

   1. We recommend you to enable EN_ASR and EN_AAR by default. However if the motor has very low inductance, we recommend to turn OFF EN_ASR and EN_AAR.

1. Even if EN_ASR and EN_AAR bit state are changed, there is no difference in PWM, phase voltage waveform, and current waveform.
   What are the expected changes?
   1. We only expect to see changes in the PWM waveform in cases where the body diode is conducting. If the customer is using sinusoidal or FOC control there will not be observable times of body diode conduction and so we do not expect the PWM waveform to look any different.
   2. In the cases of trapezoidal commutation, the observed phase voltage waveform will only be slightly different. In cases of body diode conduction with ASR/AAR disabled, the voltage will be observed at -0.7V or VM+0.7V.  With ASR/AAR enabled, the voltage will change to 0V/VM (the body diode voltage drop is removed).

Thanks,

Matt