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DRV8824: DRV8824 Overcurrent Protection(OTP) and Thermal Shutdown(TSD)

Hiroaki Yuyama TED
Expert 1720 points
Part Number: DRV8824

Dear, support team.

How long is Overcurrent Protection and Thermal Shutdown effective start?
I want to know the time to start protection.

Regardless of the value of ISENSE resistor, OTP is in the range of 1.8 A to 5 A?
If the current increases slowly, does protection take effect at the junction temperature?

We operate with a current of 0.4 A or less.
When an overcurrent flows, the capacity of the pattern layout is unacceptable.

Do you have any ideas for current protection?

Best Regards,

Hiroaki Yuyama

  • 0
    TI__Genius 14487 points
    Hello Yuyama-san,

    Thermal shutdown is not handled by timing. The device will shut down when the circuitry on the die senses a temperature at its trip point. This trip point is between 150-180 C. The die may be at this temperature depending on the combination of driving current and ambient temperature the device experiences. You are correct, the device will take effect when the junction temperature exceeds the trip point.

    You are correct, the OCP of the device will disable the outputs if it senses a large current. The threshold for this is between 1.8 A and 5 A just as you mentioned. It does not depend on the R_SENSE resistor.

    Thermal shutdown and OCP are two different protection features. Whichever one comes first will shut the device down.

    If you want to ensure that the current you drive is less than 0.4 A, then you can change the R_SENSE resistors and xVREF pin voltages to limit the current at 0.4 A. This will just ensure that your full-scale current is not greater than 0.4, but it will not act as a protection feature. See sections 8.3.2 and 9.2.2.2 in the datasheet to see how to design for this.
  • 0 in reply to James Lockridge19
    Expert 1720 points
    Hi,James-san,
    Thank you for your reply.

    Yes, we set R_SENSE resistors and xVREF pin voltage at 0.4 A.

    If it is Overcurrent conditions on both high and low side devices, that is, a short to ground, supply, or across the motor winding,
    How long will it take OCP to become analog current limit?

    I want to know the time to become H-bridge will be disabled and the nFAULT pin will be driven low.
    And if the current limit reacts quickly when the motor is short circuited.
    Does the current limit react quickly when the motor is short-circuited?

    Best Regards,
    Hiroaki Yuyama
  • 0 in reply to Hiroaki Yuyama TED
    TI__Genius 14487 points
    Yuyama-san,

    The time for OCP to disable the H-bridge is 3 us. This is the "Overcurrent deglitch time" parameter in the datasheet.
  • 0 in reply to James Lockridge19
    Expert 1720 points
    Hi,James-san,
    Thank you for your Answer.

    I did not understand that "deglitch" is the time to start Overcurrent Protection.
    But I was able to understand with your Answer!

    Best Regards,
    Hiroaki Yuyama