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DRV8873: Driver getting hot when powered and NOT driving a load

Jason Gramse
Intellectual 410 points
Part Number: DRV8873
Other Parts Discussed in Thread: DRV8876

I've designed a circuit to drive a brushed linear actuator at 28 Vm. I've got all the parts soldered onto the board. When I apply power, however, the DRV8873 gets hot even though there is no motor connected and the EN/IN1 and PH/IN2 pins are low. I'm wondering what I'm doing wrong. Here is the current design. Do you see anything obvious that needs to be changed? 

  • 0
    Intellectual 410 points

    Sorry, I just solved my own problem. From the datasheet:

    Looks like the way my circuit is configured, the OUT1 and OUT2 are both high and cannot be set to Hi-Z as the disable pin is tied to GND. Looks like I need a new board. 

  • 0 in reply to Jason Gramse
    TI__Guru** 114905 points

    Hi Jason,

    We are glad to hear you solved your problem, but there could be more.

    How hot did the device get? With the motor disconnected, there should be little current flowing to cause the DRV8876 to get hot.Please double check the layout and look for possible current flow through the motor. 

    One possible current area is the DVDD connection. DVDD appears to be connected to another 5V regulator. If it is, the connection should be removed. Keep in mind the DRV8873 requires an external signal to wake the device. nSLEEP should be connected to an external 5V signal.

    If you have space on your board, it is recommended to place footprints to allow using the various configurations available. This will prevent having another spin of the board.

  • 0 in reply to Rick Duncan
    Intellectual 410 points

    Thank you so much Rick! That was indeed the problem. DVDD was connected to a 5V regulator. After lifting this pad the problem was gone. I missed that in the data sheet. If I want my device to remain on all the time, is there any reason I shouldn't connect nSLEEP to a 5V supply? I'm running out of pins to connect a signal to.

  • 0 in reply to Jason Gramse
    TI__Guru** 114905 points

    Hi Jason,

    There is no issue connecting nSLEEP to a 5V supply, other than wasted current when the motor is not driven.

    Most times this is done through a current limiting resistor (1k for example) to prevent a short at the pin shorting the power supply.