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DRV8886: Issue with the driver

ashkan rashedi
Prodigy 110 points
Part Number: DRV8886

Hi, I am attaching my design here. It is not giving me anything in the output. Currently that 100u cap is not in place since I do not have it now, I guess that should not be the cause of my issue since that is just a noise cap. I am not connecting any motor to the output yet. I am giving 0 or 1 for direction directly from uC and generating a *** with uC for making steps. I am expecting to see pulses in the output. But I dont see anything. 

THe exact part number I ordered in Digi is DRV8886PWP, it did not pop up in the list above. 

Thanks for your help. 

Ashkan

  • 0
    TI__Guru** 114905 points
    Hi Ashkan,

    The schematic appears to be correct. Please check the VCP, DVDD, and AVDD voltages. These voltages should be present for the outputs to pulse.

    If one or all of the voltages are not present, please check the connections to nSLEEP and ENABLE.

    If the connections are correct, please check for a fault. You will need a pull up resistor on the nFAULT pin.
  • 0 in reply to Rick Duncan
    Prodigy 110 points

    Hi Rick,

    Thanks for the reply. I have soldered the pull up resistor. Also for logic pins I have changed 5V to 3.3V since I am using a 3.3V uC. According to the datasheet 3.3 is fine for DRV8886. Updated schematic is attached. 

    Also I found a cold solder and I fixed it. Now all outputs are staying high at 12V. VCP is about 23V, AVDD is about 5V and DVDD is about 3.3V. nFAULT is high at 3.3V. ENABLE and nSLEEP are high at 3.3V.

    I give a clean pulse to step but the DIR pin is just oscillating (like a noise, not pulse) from 0 to 5V. uC is OK since it is working fine (I am printing something though UART all the time). This pin was not liek that before, I understand the DRV8886 is forcing the pin to act like that!!! What would be your comment?

    Thanks

    Ashkan

  • 0 in reply to ashkan rashedi
    TI__Guru** 114905 points
    Hi Ashkan,

    DIR should not be the cause of this, as it is an input with a pulldown.

    Do you have a second board with the device populated? If so, can you try it?

    Also, is the motor connected? What is the value of R9? It should not be lower than 15kOhm.
  • 0 in reply to Rick Duncan
    Prodigy 110 points
    All values are as shown in the schematic. So R9 was 100. Now I have changed it to 240KOhm.
    The motor is not connected. Does it have to be connected?
  • 0 in reply to ashkan rashedi
    Prodigy 110 points
    I have connected the motor now it is working, but I can not change the direction. It does not matter when I change the direction since that pin is always noisy as I mentioned before!!!
  • 0 in reply to ashkan rashedi
    Prodigy 110 points
    The pin was not connected properly. Now everything works. Thanks for you help.
  • 0 in reply to ashkan rashedi
    TI__Guru** 114905 points
    Hi Askan,

    Thanks for the follow up. Glad to hear you have it working.