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DRV8842 vs DRV8841

Christopher Porter
Prodigy 80 points
Other Parts Discussed in Thread: DRV8842, DRV8841

Hello,

I was reviewing the datasheets for the DRV8841 and the DRV8842 and I noticed that the logic for the current control inputs is opposite.  I am looking to use the DRV8842 to actuate a solenoid and would like the maximum current.  We previously used the DRV8841 and pulled the current pins low for max current, I want to make sure that in the next revision of the board I will need to tie the current control pins high on the drv8842 to get the maximum.

Thanks,

Chris

  • TI__Mastermind 21805 points

    Hi Chris,

    You are correct, the DRV8841 requires pins I1 and I0 to be tied low for maximum current, while the DRV8842 needs I4...I0 to be tied high. Alternatively, you can disable the current regulation feature by grounding the ISENSE pins (no current sense resistor) and connecting pin VREF to V3P3.

     

    Matt Hein

  • in reply to Matt Hein
    Prodigy 80 points

    Matt,

    In the event that I disable the current sense should I pull the I4..I1 pins low since they serve no purpose and I would be wasting power, albeit a small amount, sending current through the devices internal pull down resistors.

    Thank you very much,

    Chris

  • in reply to Christopher Porter
    TI__Mastermind 21805 points

    Chris,

    Unfortunately, the current control inputs will take precedence in this case, so if you pull them all high then the H-bridge may turn off. For simplicity, pull one of the control inputs (say, I4) high and tie the rest low so that this will not happen.

     

    Matt

  • in reply to Matt Hein
    Prodigy 80 points

    Matt,

    I thought that pulling all the pins high would allow for maximum current, as opposed to shutting the device off.

    If I were to design the circuit with the current sense disabled and one of the current control inputs pulled high would my current be limited to 5% of the full scale current?

    Thanks for all the help,
    Chris
  • in reply to Christopher Porter
    TI__Mastermind 21805 points

    Chris,

    Sorry for the confusion. I misspoke; my last message should actually say, "if you pull them all low then the H-bridge may turn off." That was my mistake.

    If you design the circuit with the current sense feature disabled, then any configuration of I4 … I0, except for all pins pulled low, will result in an unlimited current (although the device still has overcurrent and overtemperature protection). So it doesn't really matter what percent scaling you choose, the result will be the same. Since the full-scale current is configured by placing a current-sense resistor on the ISENSE pins (and adjusting the voltage on VREF), not including the resistor means that the full-scale current is not set.

    You can pull all current control inputs high, but I suggested only one is necessary because you discussed wasting power.

     

    Matt