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DRV8823-Q1: DRV8823-Q1 output waveform

Part Number: DRV8823-Q1

Dear TI:

    My customer used DRV8823-Q1, the output waveform abnormal.

    The register configuration:

     Channel 1: {0x0083,0x00c3,0x00c2,0x00c1,0x0001,0x0041,0x0040,0x0043};//(xI2, xI1, and xI0)20%,Delay Mode= slow mode

     Channel 2: {0x1083,0x10c3,0x10c2,0x10c1,0x1001,0x1041,0x1040,0x1043};//(xI2, xI1, and xI0)20%,Delay Mode= slow mode

     The waveform as below, there is a abnormal waveform(the red circle) , one step is 10ms:

     What causes the abnormal waveform and how to solve it? Thanks!

     

Regards!

Eric Shen

     

  • Hi Eric,

    I believe this is expected, but more information is required to confirm this.

    What output voltage is captured? (AOUT1, AOUT2, BOUT1, or BOUT2)
    What was written to the registers in the step prior to the circled part of the waveform?
    What was written to the registers in the circled part of the waveform?

    It appears the output was sinking current prior to the circled part and then both outputs were disabled. Current in the coil continues to flow and causes the voltage to increase to approximately 0.7V above VM until the current reaches 0.
    The outputs are now Hi-Z and the next part of the waveform is the back EMF.
  • Hi Rick:

       FYI:


       What output voltage is captured? (AOUT1, AOUT2, BOUT1, or BOUT2)----AOUT2
       What was written to the registers in the step prior to the circled part of the waveform?----0X0083
       What was written to the registers in the circled part of the waveform?----0X00C3

  • Hi Eric,

    This still does not make sense.

    0x0083 should be AOUT2 low as shown
    0x00C3 should be AOUT2 low also

    The image makes sense if the registers were changed from 0x0083 to 0x0082. It looks like the AOUT was disabled in the circled area.

    Would you please check again? Thank you.
  • Hi Dick:

      The registers value is right, I has check with customer.

       Customer give me 8 steps registers configuration as below:

       Channel 1: {0x0083,0x00c3,0x00c2,0x00c1,0x0001,0x0041,0x0040,0x0043};//(xI2, xI1, and xI0)20%,Delay Mode= slow mode

       Channel 2: {0x1083,0x10c3,0x10c2,0x10c1,0x1001,0x1041,0x1040,0x1043};//(xI2, xI1, and xI0)20%,Delay Mode= slow mode

        And the red circled area is step 1+step 2, the eight blue arrows represent the eight steps, and there are another abnormal waveform in yellow pane, two small low pluse. So what is the pluse?

       

        Thanks!

    Regards!

    Eric Shen

  • Hi Eric,

    I went to the lab, and I was not able to duplicate this waveform.

    When I sent 0x83 and 0xc3, AOUT2 remained low.

    At this time, the most likely explanation for the circled area remains the same as the original response. If the outputs are being disabled, current in the coil continues to flow and causes the voltage to increase to approximately 0.7V above VM until the current reaches 0. The outputs then are Hi-Z and the next part of the waveform is the back EMF.

    Is it possible to capture the serial transaction that cause the circled area to occur? If slow please zoom in and provide the scope capture.

    To determine the cause of the small pulses, please zoom in on this area and provide a scope capture of the small pulse plus the serial transaction. How is SSTB connected?
  • Hi Eric,

    As we have not heard back, we are assuming the issue has been resolved. If it has not, please reply or if the post is locked select "Ask a related question".
  • Hi Rick:
    Thanks! Customer pending this issue now, if customer need support, i will to trouble you again.

    Regards!
    Eric Shen