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DRV8308: Powering Hall sensor from Vsw or Vreg

Sal LaRussa
Genius 9690 points
Part Number: DRV8308

We recommend adding resistor between Vreg or Vsw and hall sensor.

Have we seen damage to hall sensors without this resistor in place?

Thanks,

Sal

  • 0
    TI__Mastermind 21805 points

    Hi Sal,

    You need to have a resistor between VSW and the Hall elements because the Hall elements need to be biased below the abs max ratings of UHP/UHN comparator input pins. If there is no resistor between VSW and the Hall element then the Hall element output will be sitting at VSW, which is a high voltage. I have seen some customers omit the resistor between the Hall elements and ground because then the halls get biased close to ground, which is OK for the hall comparator input pins.

    If the customer is using a Hall sensor rather than a Hall element, no resistor is required, since the current limitation is done inside the Hall sensor and the Hall output is open drain.

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    TI__Genius 9690 points

    Thanks for the quick reply Matt.   Given that the ABS MAX on our hall sensor inputs (UHP/UHN) is Vreg, I would assume no resistor is needed if powering the hall element from Vreg, correct? 

  • +1 in reply to Sal LaRussa
    TI__Mastermind 21805 points

    Hi Sal,

    The voltage would be in the right range if you power directly from VREG, but you'd still need to limit the current if a hall element is used. Normally the hall element has some bias current specification and you need to add a resistor to make sure you don't blow it up with too high of a bias current.

    With a hall sensor, you don't need to do any of that so you can directly connect it.

    Thanks,

    Matt