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DRV8313: Highcurrent Issue

Part Number: DRV8313

Dear Sir,

I tried running the motor with two pieces of hardware available with me.
1. Motor is running with STSPIN233, Current is drawing at 8VDC is 0.25 A.
2. Motor is running with DRV8313, Current is drawing at 12VDC is 1.10 A.

The motor is the same, the Microcontroller is the same, and the Software/Firmware of PWM logic is the same.

The Schematic is the same, I shared earlier.

Please let me know, What will be the possible reason?.

Regards
Murthy

  • Hi Murthy,

    Thanks for posting your question to the e2e forum - we are looking into this and will follow up with some feedback in the next two days 

    Thanks and Best regards,
    Andrew

  • Hi Murthy,

    Please see the below answer to your question.

    In the case of motor phase current, it is usually determined by variables such as

    • the motor operating supply voltage,
    • the motor operating speed and backEMF voltage, and the motor loading, and the motor wiring & motor itself. 

    In your mentioned case, DRV8313 is being operated at 12V supply vs the STSPIN233's 8V.

    This alone would have a big impact on the motor phase current, even if we are keeping the other variables the same. 

    Hope that helps clarify the situation, and let us know that answers your question.

    Thanks and Best Regards,
    Andrew

  • Dear Sir,

    Now, I operated both Ic's at same voltage 8VDC,Still DRV8313 taking 3 to 4 times more current.

    Regards
    Murthy

  • Hi Murthy,

    Thanks for the update - 
    Would it be possible to share a schematic (and maybe layout) of both designs, so that we can look for potential root causes? 

    Thanks and Best Regards,
    Andrew

  • Dear Sir,


    Please share your email ID
    I will share the schematic through email.


    Thank You!


    Regards
    Murthy

  • Hi Murthy,

    sent you a private message over e2e - will follow up there & via email

    Best Regards,

    Andrew 

  • Hi Murthy,

    Thanks for your patience - 

    I took a look at the schematics you sent over, and did have some follow-up feedback and questions. 

    1. Question regarding current measurement
      1. are you saying that you are seeing the 0.25A/1.1A as the current going into the motor phase, measured at OUT1/2/3 pins?
      2. or are you saying that this current is just what you're pulling from your main power supply? (to power the entire system)
      3. The current draw going into the motor itself is dependent on those factors I mentioned earlier, like operating voltage and speed and backEMF, motor wiring and loading, etc.. 
      4. I am wanting to clarify if this excess current is all going into the motor, or if it is conducting through some other part of the system through a high-leakage path, which might explain why the power supply is drawing so much current elsewhere. 

    2. Things I noticed on the schematic:
      1. observed that the V3p3 regulator pin only has 100nF of capacitance on it, instead of the 0.47uF cap to GND recommended in the datasheet
        1. can you try correcting this capacitor value, and let me know if it changes the performance of the system? 
      2. observed that you have a 0.1uF bypass cap on VM, but no 10uF bulk capacitor. 
        1. do you have any bulk capacitors between the VM pin and GND?
        2. The datasheet section 9.1 mentions the purpose for this 
    3. Misc question about motor operation 
      1. what was the switching frequency used for both motor driver devices?

    Thanks and Best Regards,
    Andrew

  • Dear Sir,


    1. Are you saying that you are seeing the 0.25A/1.1A as the current going into the motor phase, measured at OUT1/2/3 pins?
    Not motor phase current, Its total current pulling from your main power supply.


    2. I am wanting to clarify if this excess current is all going into the motor, or if it is conducting through some other part of the system through a high-leakage path, which might explain why the power supply is drawing so much current elsewhere.

    We will test and update you Sir


    3. observed that the V3p3 regulator pin only has 100nF of capacitance on it, instead of the 0.47uF cap to GND recommended in the datasheet.

    Noted, we change the Capacitor


    4. do you have any bulk capacitors between the VM pin and GND?

    Yes,330uF,25V DC bulk capacitor connected across the power rail


    5. what was the switching frequency used for both motor driver devices?
    Switching Frequency:16KHZ

    Regards

    Murthy

  • Thanks Murthy

    Looking forward to an update on your progress - I will keep looking into this further as well.

    One thing that will help us debug is to determine where the current is going in each case below:

    • total current draw from main power supply is ~1A from earlier comments 
    1. how much of that current is going into the motor phase windings, exactly, through OUT1/2/3
    2. how much of that current is being sinked into the DRV device's VM pin(s) specifically 
    3. how much of that current is being routed elsewhere to possibly damaged components elsewhere

    Items #1,2 above are usually predictable, so I am curious as well as to where all the excess current is going.
    At the very least, if DRV device current draw and motor phase current are reasonable, then we can be more confident that the DRV device and motor are not damaged, and then localize the problem to some other part of the circuit 

    Lastly, one other question I wanted to ask is whether the motor operation is fine (able to spin a motor smoothly) with the DRV8313 device

    • or if there are possibly some other strange waveforms like transients and spikes on the VM power supply bus? 

    Best Regards,
    Andrew

  • Dear Sir,

    Thank you so much for your warm reply to all my questions.
    The issue is resolved in our PCB.

    Regards
    Murthy