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DRV8889-Q1: the time of open load detection

Longbiao Liu
Prodigy 50 points
Part Number: DRV8889-Q1

Hi expert,

there are some questions about the open load detection time of DRV8889, In the data sheet it is written that“if this condition persists for more than the open load detection time (tOL), an open-load condition is detected”，According to the explanation of this sentence, the time from the actual load opening to the time when the chip detects a fault and pulls down the nFAULT should be greater than T_ol. 

But it is written later in the data sheet that T_ol is the maximum detection time, and I also tested during the  test that the actual open load detection time is less than T_ol.

I wonder if there is a contradiction between these two instructions in the data sheet?

What should the actual open load detection time be based on?

In addition, the host computer software provided by the official website cannot modify the OL_TIME register to change the open load detection time, whether some methods can be provided？

thanks!

  • 0
    TI__Mastermind 44595 points

    Hi Longbiao,

    Thank for posting this question. See below snippet from the datasheet specifications. The tOL max. spec is given just so the user knows that would be the worst case OL detection time. The actual tOL could be lower. In other words typical tOL (typ.) is < tOL (max.).

    Please also note under certain conditions a false OL may be indicated. 

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    TI__Prodigy 50 points

    thank you for you reply. I have some more needs for the "DRV8889-Q1EVM-GUI-cloud", It is not possible to change the time of the open load detection in this software. Can you give me some other method? thanks.

  • 0 in reply to Longbiao Liu
    TI__Mastermind 44595 points

    Hi Longbiao,

    These bits are reserved bits RSVD in the DRV8889-Q1. You cannot modify these bits. See below snippet.

    They can be modified for the DRV8889A-Q1. See below snippet. EVM not available with this 'A' variant. If you're willing to rework the DRV8889-Q1 EVM with a DRV8889A-Q1 device sampled from TI, let me know. I will give you access to a cloud based GUI that will allow you to modify these bits.

     

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    TI__Prodigy 50 points

    Hi Murugavel,

    Is the open load detection time for DRV8889- q1 therefore not possible to change? What is the maximum time? 200ms? 

    If I want to change this time, do I need to replace DRV8889-q1 on the EVM board with DRV8889A-q1 first? 

    best regards

  • 0 in reply to Longbiao Liu
    TI__Mastermind 44595 points

    Hi Longbiao,

    Yes, your both comments are correct. After replacing and getting it to know you should use a different GUI I can get you access if you'd want to do that. First step is to replace the device and get the EVM working with the existing cloud based GUI.

    Regards, Murugavel