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DRV8316C: ASR and AAR enable will not lead to 0V drop on LS FET if negative current is applied

Florian Rösel
Prodigy 50 points
Part Number: DRV8316C

Hello,

currently we are exploring the DRV8316C and its ASR/AAR features. We are using 6xPWM Mode, not using the internal cycle-by-cycle current limitation. CSA_GAIN is 0x0, ILIM_RECIR is 0x0.

To verify the correct working of the feature, we want to set all PWM inputs to LOW. Afterwards we apply a negative current to OUTA, and expect a voltage drop induced by the body diode of LS-FET A around -0V7.

Our measurements confirm, that there is a voltage drop ~0V7 if we limit the negative current to ~1A.

Afterwards, we configure 0x07=0x0C (Control Register 5, EN_ASR and EN_ASS=0b1) and expect a voltage drop ~0V. We read back the register and the result of CCR_5 is the expected value (0x0C).

Unfortunately, we can not confirm that the voltage drop will decrease, too.

Could you please clarify, why we do not see 0V thous we enabled ASR/AAR?

Thanks,

Florian

  • 0
    TI__Expert 8401 points

    Hi Florian, 

    Thank you for your question.  

    Can you please clarify further this point: 

    Florian Rösel said:

    Afterwards, we configure 0x07=0x0C (Control Register 5, EN_ASR and EN_ASS=0b1) and expect a voltage drop ~0V. We read back the register and the result of CCR_5 is the expected value (0x0C).

    Unfortunately, we can not confirm that the voltage drop will decrease, too.

    What voltage are you measuring back instead of 0V? 

    Best Regards, 

    -Joshua

  • 0 in reply to Joshua Maize
    Prodigy 50 points

    Hi Joshua,

    we measure OUTA  <-> GND. There we measure -0V7, which seems to be the body diode voltage. Independently which value we are setting in Control Register 5 (offset 0x07) the EN_ASR and EN_ASS Bits. To confirm we set the bits correctly, we read back the values of the register and got the expected bit set.

    Best Regards,

    Florian

  • 0 in reply to Florian Rösel
    TI__Expert 8401 points

    Hi Florian,

    Thanks for the clarifying info. 

    Allow me to look into this matter this week and follow-up.  I'll respond if there are any supporting questions necessary to help resolve this. 

    Best Regards,

    -Joshua