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DRV8847: About connecting the output port of a microcomputer to nSLEEP of 4 DRV8847PWR

user5308758
Prodigy 120 points
Part Number: DRV8847
Hi,
We are considering switching the operation / sleep of 4 DRV8847PWRs by connecting the 1 output port of microcomputer to four nSLEEP ports and switching the one output port of microcomputer high / low.
I have a few questions about this.
1.Are there any concerns or additional parts (e.g. need a pull-up resistor)
2.The difference between "keeping nSLEEP always high (maintaining the operation mode) and making nSLEEP high only when operating DRV8847PWR" is Standby power consumption (If nSLEEP is set high even when not operating, standby power is wasted).Is this recognition correct? Are there any other concerns?
Best Regards.
  • 0
    TI__Expert 8985 points

    Hi user,

    Answers inline.

    1.Are there any concerns or additional parts (e.g. need a pull-up resistor)
    HH-> Your supply needs to account for the the 4 VM operating currents, the current each of the four nSLEEP pins consume, and the minimum VIH voltage required for nSLEEP to be recognized high. 
    2.The difference between "keeping nSLEEP always high (maintaining the operation mode) and making nSLEEP high only when operating DRV8847PWR" is Standby power consumption (If nSLEEP is set high even when not operating, standby power is wasted).Is this recognition correct? Are there any other concerns?
    HH-> If a fault occurs, the only way you can reset it is by resetting nSLEEP or turning off VM. You will need to turn off VM if nSLEEP will always be high and a fault occurs. Another concern: are you utilizing 2-pin MODE for this design? If so, IN3 must be tied low and the only way to decay the current is to pull nSLEEP low.
  • 0 in reply to Hector Hernandez Luque
    Prodigy 120 points

    Hi,

    There are four types of faults.
    1.UVLO recovers when VM is above VUVLO(nFault L→H).
    2.OCP recovers after tRETRY(nFault L→H).
    3.OLD recovers after Power reset or Device comes out from sleep mode.
      Even if OLD occurs, the internal circuit and H-Bridge operate normally(But nSleep maintains L).
     To return nSleep to H, it is necessary to turn off the power or enter sleep mode
    4.TSD recovers whenTj is below TTSD-THYS(nFault L→H).
    Is the above recognition correct?
    We are using 4pin mode.
    And fault condition indication by nFualt pin is not used.
    Best Regards.
  • 0 in reply to user5308758
    TI__Expert 8985 points

    Hi user,

    If OLD occurs, nSLEEP remains logic high. To clear the fault report, you need to either power cycle or reser (RESET) the nSLEEP pin to Low, then back to High. nSLEEP is an input and you have control over it. The device does change its function (it has a pulldown resistor, so it will be pulled low if you do not drive it).