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DRV10975: AVS and register programming on DRV10975

Christina Lim
Expert 5065 points
Part Number: DRV10975

Hi,

If I have system with input voltage (VCC) is 12V, if the VCC voltage is cut, will the AVS function still work? When does the IC cut off this functionality?

On the programming, how does the different modes affects the register programming :

1. If I exit standby mode, do I need to re-program the driver IC parameters?

2. If I use the DRV10975 variant which has the sleep mode, do I need to re-program the driver IC parameters when I exit sleep mode?

Thanks,

Christina

  • 0
    TI__Mastermind 21805 points

    Hello Christina,

    Thanks for your question.

    Mechanical AVS doesn't cover the case where power is cut because it uses Ke estimation to make that decision - the driver needs to be powered ON and current needs to be sensed.

    The DRV10975 has EEPROM (NVM) which can be configured, so you do not need to re-program the parameters for power down, sleep mode, or standby mode once the EEPROM is set.

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    TI__Expert 5065 points

    Hi Matt,

    Since Inductive AVS is not available for this device, does this mean the device is not protected from inductive energy flyback from the motor BEMF?

    What recommendation do we provide to customer on system level protection against inductive flyback?

     

    Thanks,

    Christina

  • 0 in reply to Christina Lim
    TI__Mastermind 21805 points

    Hi Christina,

    No, this device will not prevent inductive energy from pumping up the supply.

    As a system level mitigation we do recommend sizing the supply bulk capacitors appropriately to absorb the energy without exceeding the abs max ratings of the IC. As a last resort, a TVS can be added to clamp the supply voltage.

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    TI__Expert 5065 points

    Hi Matt,

    Do we have any application notes on the calculation for the bulk caps and the TVS for clamping supply voltage?

    Thanks,

    Christina

  • 0 in reply to Christina Lim
    TI__Mastermind 21805 points

    Hi Christina,

    Unfortunately we do not have any documents on the subject. In general VCC should be clamped to less than the abs max rating of the device.

    You can approximate bulk capacitance through energy transfer equations. C (dV)^2 = L (Irms)^2 + (moment of inertia) * (speed)^2. dV is the approximate increase in voltage. This depends on the motor inductance, RMS current, and the energy stored in the motor while coasting. This is a worst case approximation, since all of the motor energy will not result in supply voltage increase and the motor supply will be able to absorb some or all of the energy.

    Thanks,

    Matt