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DRV8313: Connecting nSLEEP, nRESET & nFAULT together

Eddie Koh
Genius 10635 points

Part Number: DRV8313

Would it be ok to connect all of nSLEEP, nRESET and nFAULT together, to an MCU weak pullup high to enable and the nFAULT can still pull low to indicate a fault?

Breaking the question down into 3 stages:

1. Tie nSLEEP & nRESET together

2. Connect nSLEEP & nRESET to nFAULT 

3. Tie all 3 signals to MCU with weak pullup 

     -3.1 MCU will pull all 3 signals high (when there is no fault)

     - 3.2 nFAULT's 10mA capability will pull MCU's GPIO + Weak pullup to logic low during fault

Notes:

nFault is OD with 10mA

MCU GPIO is weak pull up ~0.1mA equivalent

  • 0
    TI__Mastermind 18981 points

    Hi Eddie, 

    We will aim to give you an answer on this by early next week 

    Best Regards, 
    Andrew 

  • 0
    TI__Mastermind 29686 points

    Hi Eddie,

    Sorry for the delay in responding to you! I do not recommend connecting nSLEEP, nRESET, and nFAULT together. nSLEEP is used as an input to put the device into sleep mode, which shuts down much of the device internal circuitry for low power consumption. The nRESET pin is an input to reset faults, and nFAULT is an open drain output to report faults. By connecting nFAULT to nSLEEP and nRESET, this creates a condition where when a fault occurs and nFAULT goes low, that will also put the device into sleep mode and also try to reset faults at the same time. Once the fault is cleared either due to nRESET going low or the device entering sleep mode, then it either may try to pull nFAULT back high, or it may not due to nSLEEP being low. The exact behavior of the device in this condition is not something that I have tested, and I wouldn't recommend this. I would connect each of the pins to their own dedicated GPIO. Additionally, using the weak pullup of the MCU is not the best idea since this may result in a slow recovery time of the nFAULT signal since the equivalent resistance of a 0.1mA pullup is about 33k ohms, which may result in a longer time for the pin to be pulled up compared to a 10k pullup resistor that is recommended for nFAULT. 

    Regards,

    Anthony Lodi