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DRV7781

Other Parts Discussed in Thread: DRV8871

Hi,

I have the following questions on DRV8871.

Is there any protection given for the shorting of supply voltage with any one of the output?

Is there any EMI/EMC guidelines or suggested filters for the driver outputs (i.e. OUT1 & OUT2)?

What is the resistor value shown in the data sheet, section 7.3.1, Figure:4 ?

  • Hi Suresh,

    suresh p33 said:
    Is there any protection given for the shorting of supply voltage with any one of the output?

    There is overcurrent protection. If the output is shorted to the supply and draws more current than the maximum overcurrent level for the OCP deglitch time, the outputs will be disabled.

    suresh p33 said:

    Is there any EMI/EMC guidelines or suggested filters for the driver outputs (i.e. OUT1 & OUT2)?

    These guidelines are not provided. You may consider contacting your motor manufacturer for suggestions.

    suresh p33 said:

    What is the resistor value shown in the data sheet, section 7.3.1, Figure:4 ?

    Thank you for pointing this out. The resistor should not be there. It will be removed in a future update.

  • Thanks for your detail on protection and suggestion for EMI/EMC guidelines.

    I have seen DRV8871 failure during the power ON.
    I have analyzed and found there is an external short between OUT1 and ground in the board. Due to that DRV8871 flashed.
    The supplied voltage with 24VDC and both the inputs are pulled high during initialization.

    Is there any worst case scenarios tested ?

    Why it was failed and is there any analysis for the same?
  • Hi Suresh,

    Can you provide a few more details?

    Did the external short between OUT1 and ground in the board exist before the failure?
    Were the inputs ever set to enable the device?
    What is the current rating of the power supply?
  • Yes, it was happen during testing on general purpose prototype board.Before switched ON there was a short between OUT1 and ground that didn't observed. i have connected the motor load of 200mA and Powered ON ,suddenly DRV8871 was flashed. I verified checked that short between OUT1 and ground. i removed DRV8871 from the board , still short was there between these signals. Removed the stagnated extra lead in the general purpose board between these lines and connected a new sample of DRV8871. Now it is working normal.

    During Power ON I have connected the inputs from different Power supplies ( One from micro controller board I/O and other one is pull-up from DRV8871 Kit existing 5V supply).In our application running the motor in one direction.

    The current rating of power is 250mA maximum.

    Is there any protection that you can suggest?

    I hope have provided enough information and please let me know the failure details of the drive.
  • Hi Suresh,

    What is the Rlim resistor value?

    If your motor requires 250mA, try using a resistor set to approximately 300mA (~210kOhm). This allows some variation of motor current, but should protect against shorts by chopping the current.