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DRV8874: Level question of OUT1 and OUT2 in sleep state

Lee HongGyo
Prodigy 210 points
Part Number: DRV8874

I inquire about the output level of OUT1 / 2 when DRV8874 Sleep status.


The operating conditions are as follows.
PWM mode
Bidirectional structure


The operation sequence is as follows.
Sleep --> Brake --> Forward --> Brake --> Sleep


Description of the picture below
When Sleep is set to 1, Out1/2 drops to 0V (brake state).
If Forward, the Out1/2 level is maintained at 12V for 15mSec ( Forward state)
When you brake, the Out1/2 level drops to 0V. ( Brake state).
When Sleep is set to 0, Out1/2 becomes about 4.7V (Sleep state).

Questions
I inquire if it is normal for Out1/2 to be about 4.7V when Sleep=0.

  • 0
    TI__Mastermind 37683 points

    Hi Lee,

    Lee HongGyo said:
    I inquire if it is normal for Out1/2 to be about 4.7V when Sleep=0.

    Out 1 and 2 will be in a high impedance (High-Z) state when nsleep=0V. Typically, if there is nothing pulling the outputs to a non-zero voltage, the OUT1/2 voltage should be zero. Can you share the output driver stage of your design? Do you have any other components connected to the OUT1/2 outputs aside from the load?

  • 0 in reply to Pablo Armet
    Prodigy 210 points

    Thank you for answer.
    The output stage configuration is shown in the figure below.
    When nsleep=0V, OUT1/2 is High-Z, so you replied that OUT1/2 is normally 0V.
    But in my case, when nsleep=0V, OUT1/2 is about 4.7V.
    I'm suspecting the diode as the reason OUT1/2 doesn't go to 0V based on your comment.
    This diode is a Schottky diode. I think it's because of Leakage Current.
    I will reply with the result after removing this diode.

    additional questions
    When nsleep=0V, OUT1/2 is High-Z, so OUT1/2 is usually 0V. As in this case, if it is 4.7V, I ask if it is a problem with the DRV8874 IC.

  • 0 in reply to Lee HongGyo
    Prodigy 210 points

    I simulated the drv8874 using the TI PSpice model.
    It was confirmed that OUT1/OUT2 outputs 0V when there is no Schottky diode in the output in the sleep state.
    If there is a Schottky diode at the output in the sleep state
    It is confirmed that OUT1/OUT2 outputs about 6V.
    It can be seen that the simulation results with Schottky diodes are very similar to the actual measurement results.
    So I will remove the diode and measure it.
    A Schottky diode is inserted for the purpose of IC protection against the inductive load.
    I know there is a MOSFET body diode inside the DRV8874, but
    I put a Schottky diode on the outside to protect the IC.
    From an inductive load and external ESD point of view, is the IC ok without an external Schottky diode?
    If the output is 4.7V in Sleep state, is there any problem with the DRV8874 IC?

  • +1 in reply to Lee HongGyo
    TI__Guru 54645 points

    Hello,

    There is no problem for the IC.  It is an acceptable condition.

    Regards,

    Ryan