This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8870: OUT1 or OUT2 short o GND

Part Number: DRV8870

Hello Support team,

I intentionally made the OUT1 terminal or OUT2 terminal short-circuited to GND and operated Forward and Reverse.
The assumption was that overcurrent would occur and OCP or OTP would work, but no current flows at all, and it seems that some protective function is working.
What kind of control is being done?
In addition, it will operate normally if the GND short state is released. The device seems to have non damage.

Best Regards,
Hirokazu Takahashi

  • Hi Takahashi-san,

    The outputs have overcurrent protection. If the current through either a high side or low side FET exceeds the overcurrent level for more the overcurrent deglitch time, the outputs will be disabled for 3ms.

    Please examine the outputs voltages with a scope. You will may see one of the outputs attempting to enable.

    The current flow will be very little since the current only flows for 0.05% of the time.

  • Hello Rick -san

    Thanks for you support.
    According to datasheet, OCP is defined as 4.5A@typ.
    But we couldn't find such over current.
    How do you think it?

    I couldn't understand your comment below.
    "The current flow will be very little since the current only flows for 0.05% of the time."

    Best Regards,
    Hirokazu Takahashi

  • Hi Takahashi-san,

    According to datasheet, OCP is defined as 4.5A@typ.
    But we couldn't find such over current.
    How do you think it?

    To see this current you need either a current probe, or to measure the voltage across the ISEN resistor if the resistor is installed.

    The current will only be available for ~1.5us.

    Please refer to Figure 13 of the datasheet (OCP with 45V and the Outputs Shorted Together) as an example. The current peaks at ~10A and the outputs are disabled due to the overcurrent event.

    I couldn't understand your comment below.
    "The current flow will be very little since the current only flows for 0.05% of the time."


    Sorry, I was not clear. If you are trying to measure the average current using a DMM or power supply, the reading will be very small because the current is only driven into the short for a small percentage of time. 1.5us (Tocp) / 3ms (Tretry) = current duty cycle of 0.05% when a short is present.

  • Hello Rick -san

    Thanks for your support.

    Our measurement waveform is here.


    191218_DRV8870_output short.pptx

    We couldn't find any output current at the forward term.
    How do you think about this phenomenon?

    Best Regards,
    Hirokazu Takahashi

  • Hi Takahashi-san,

    During the forward term, the OUT1 high side FET will turn on for ~1.5us and then turn off for ~3ms.  The process will then repeat. This is very difficult to see unless you are zoomed in.

    The high side FET will turn on, but the voltage at the output may not increase significantly.

    It is easier to look for current flow.