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DRV8801A-Q1: Effects of exceeding abs. max. ratings and driving in continuous overcurrent, short-circuit

Part Number: DRV8801A-Q1

Hello,

I'm facing following questions regarding DRV8801A-Q1 you may help with:

  • How would the lifetime of the driver be affected if it experiences a continuous overcurrent at the H-bridge outputs? I.e. if the driver will keep retrying indefinitely?

  • In case of a short circuit (in the driver IC), is there a risk that the part will catch fire?
    • If yes, how will the driver behave (open-mode or short circuit)?

  • What is the consequence if the supply voltage pin experienced a transient voltage higher than 40V?

Best Regards, Martin

  • Hi Martin,

    "How would the lifetime of the driver be affected if it experiences a continuous overcurrent at the H-bridge outputs? I.e. if the driver will keep retrying indefinitely?

    In case of a short circuit (in the driver IC), is there a risk that the part will catch fire?
    If yes, how will the driver behave (open-mode or short circuit)?"

    The device is designed to protect itself by limiting the current in the event of a short circuit, and allow the heat inside the device to dissipate from the short circuit event before retrying. nFAULT is asserted to notify the system of a fault.

    There should be no risk in normal operation.


    "What is the consequence if the supply voltage pin experienced a transient voltage higher than 40V?"

    Please see footnote (1) below the Absolute Maximum Ratings table of the datasheet:

    (1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
    only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
    Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
  • Hello Mr. Duncan,

    I have a fellow-up questions about the driver,

    (1) It is still unclear for me what will happen if the driver experienced a transient voltage higher than 40V? will the driver internal circuit get short-circuited (which means it would be a potential fire hazard)?

    (2) If there was no Microcontroller that checks the nFAULT pin and there was short circuit at the motor, I know the driver will switch OFF the outputs if the current if more than I(PEAK) and wait for a time t(OCP) and then retry again. If this cycle continues indefinitely, what will happen to the driver's lifetime?

    I hope you can help me with these questions.

    Thanks
    Mohamed Elamin
  • Hi Mohamed,

    Mohamed Elamin said:
    (1) It is still unclear for me what will happen if the driver experienced a transient voltage higher than 40V? will the driver internal circuit get short-circuited (which means it would be a potential fire hazard)?

    • It is possible for transient to cause electrically induced physical damage 

    Mohamed Elamin said:
    (2) If there was no Microcontroller that checks the nFAULT pin and there was short circuit at the motor, I know the driver will switch OFF the outputs if the current if more than I(PEAK) and wait for a time t(OCP) and then retry again. If this cycle continues indefinitely, what will happen to the driver's lifetime?

    • The driver’s lifetime will be impacted. 
    • The driver is specified with recommended operating conditions of up to 36V.  Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

    What is the specific concern you have? Have you added any additional circuitry to avoid the supply voltage transient?

  • Hi Rick,

    Thank you for the reply.

    Rick Duncan said:

    Have you added any additional circuitry to avoid the supply voltage transient?

    I have a filtering circuitry before the input voltage pin VBB. I use couple of inductors and a bi-directional TVS to protect the input voltage.

    Rick Duncan said:

    What is the specific concern you have? 

    We are trying to determine what will happen at the motor driver in the worst case scenario (i.e. the filtering circuitry is not working as it should). What is the fire possibility if the IC got damaged through a transient pulse?

    Best wishes,

    Mohamed

  • Hi Mohamed,

    It is difficult to speculate if there is a fire hazard if the IC is damaged due to a transient pulse.

    A transient can result in a short or open. If a short occurs, current can flow through the device in an uncontrolled path. Depending on the current, the device may act like a resistor or a fuse.


    For that reason, it is recommended to have protection circuits.

    The blog e2e.ti.com/.../motor-drive-forum-top-faqs-3-methods-to-prevent-electrical-overstress has a few recommendations to protect against electrical overstress. Adding a fuse is also a good idea.
  • Thank Rick for you response.

    We implemented all protection mentioned in the link.
  • Hi Rick,

    one last question aboutA colleague of mine told me in their High Side Switch application note, they have a test "Short Circuit characterization according to the AEC_Q100-012" where it says that the maximum number of cycles in the Short circuit mode is around 20,000 cycle. I have attached an application note from TI that does this test

    Do you know how many cycles would the DC Motor driver last if it got stuck in the endless over-current protection mode?

    Thank you.

    Mohamed

    Attachment:

    slva709.pdf

  • Hi Mohamed,

    There does not appear to be any information regarding this.