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DRV8323R: drv8323RS Missing decoupling in DVDD

jinsu park
Prodigy 20 points
Part Number: DRV8323R

I am using drv8323rs partnumber. Due to a design mistake, I did not include the DVDD's decoupling capacitor in the artwork. At this time, when operating the motor, an unknown offset was detected in the motor current depending on the power on/off. This should not be related to the DVDD, but it is shown in the experimental results. I'm curious why the presence or absence of a DVDD decoupling capacitor makes such a difference.

  • 0
    TI__Genius 15075 points

    Hi Jinsu,

    In most regulators, there's a cap at the output to act as the storage and filtering element. The decoupling capacitor on the DVDD is used to stabilize the feedback loop for the internal regulator. The device could potentially be damaged by removing the decoupling capacitor.

    Regards,

    Yara

  • 0 in reply to Yara Al Shami
    Prodigy 20 points 
    First of all, thank you for your reply.
I do not use the power output from the DVDD externally.

Even looking at the block diagram in the datasheet, I couldn't find where DVDD was used.

Still, it was confirmed that there was an unknown offset in the current detection.

Should this also be considered an effect of the DVDD's decoupling capacitor?
  • +1 in reply to jinsu park
    TI__Genius 15075 points

    Hi Jinsu,

    Whether or not you are actually using DVDD output it is still recommended to follow the guidelines found in the datasheet. As described in the pin out table, which is not very obvious, the DVDD regulator is also used internally by the DRV as well (The DVDD LDO has an internal body diode from DVDD to VM). Therefore, the external decoupling capacitor is still needed as the digital core will depend on this rail and pull current from it during operation.

    In regards to your offset issue I recommend reading the following section in the datasheet: 8.3.4.3 Auto Offset Calibration

    This should be able to help with calibrating the offset

    Regards,

    Yara