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Original question:

DRV8871: DRV8871

DRV8871: DRV8871

Michel Da Silva
Prodigy 110 points
Part Number: DRV8871

Hi,

 On a project, I use a DRV8871 to drive a DC motor.  here below,  the partial schema is showed

I link up the "IN1" pin to a 5V source by an external wire. When I power up the 24V source and the 5V source simultaneously, the motor start.

When the voltage is good, I switch "IN1" off. The motor stop

After a time (10s-20s) , I switch "IN1" on. The motor don't start.

I don't understand why !

Have you some idea on my problem?

best regards

M. Da Silva

  • 0
    Prodigy 110 points

    Here the partial schema

  • 0 in reply to Michel Da Silva
    TI__Guru** 114905 points
    Hi Michel,

    If you are powering up the 24V and 5V simultaneously, the motor is attempting to start at ~6.5V.
    When starting at 6.5V, the motor current is probably less than the overcurrent trip point.
    When starting at 24V, the motor current is probably greater than the overcurrent trip point.

    This can be checked by monitoring the OUT1 and OUT2 signals. At 24V, look for a small pulse on OUT1 (~3us) repeated every 3ms. If you see this, it is an indication of an overcurrent event.

    The overcurrent event can either be caused by the motor or a capacitor placed across the motor.
  • 0 in reply to Rick Duncan
    Prodigy 110 points

    Thank you for the answer.


    I monitored the OUT1 and I saw small pulse (2-3µs) repeated every 3ms. The motor used during test have an internal protection electronic and I suppose a capacitor is present.