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DRV8311: Driver consumes a lot of current and heating up.

Radomir Pans
Prodigy 90 points
Part Number: DRV8311
Other Parts Discussed in Thread: DRV8305-Q1EVM

Hi,

We are using the following chip DRV8311HRRWR to drive a custom-made motor. The problem we have is that the motor driver is heating quite a lot.

The total current of the board is about 147mA:

  • Idle current: 23mA
  • Driver + motor: 124mA


After a few measurements, we saw that about 50% of the driver + motor current is dissipated into the driver chip, more or less 60mA. This causes the driver to heat up and reduces the efficiency of the application. This is a significant issue, especially since it's a battery application.

  • We have already tried different dead-time settings.
  • We have analyzed if the PWM input is correct.
  • We tried to play with different PWM speeds (40kHz and 80kHz).
  • We checked if the phases are 120 degrees apart from each other.

The layout could be improved in terms of heat dissipation. There are no thermal pads under the exposed pad. This will be changed in the next iteration.

Do you maybe have any clue why the chip is heating so much?

If you need more information, please let me know.

  • 0
    TI__Expert 6491 points

    Hi Radomir,  

    Thank you for your question!  

    Let me look over your given information and provide a suggestion as soon as I can this week.  

    I will say now that adding thermal pads and more copper pours/stitching vias is one big way to help with layout thermals. 

    Best Regards, 

    -Joshua 

  • 0 in reply to Joshua Maize
    Prodigy 90 points

    Hi Joshua, 

    Did you get the chance to look into it? 

    If you need more information, feel free to ask :) 


    With kind regards, 
    Radomir Pans 

  • 0 in reply to Radomir Pans
    TI__Expert 6491 points

    Hi Radomir,  

    Thank you for your patience and sorry for the delay! 

    After review of your schematic it appears to be fine,  and your chosen parameters (lowest slew rate,  40kHz PWM,  etc)  are should not lead to this issue.  

    I believe that layout optimization may be the most important factor,  and this motor drive layout document here will be helpful as you design the next iteration. A possible source of heating to look into could be traces that are too narrow for the amount of current flowing. 

    Let me know if I can help further as we work on optimizing.  

    Best Regards, 

    -Joshua 

  • 0 in reply to Joshua Maize
    Prodigy 90 points

    Hi Joshua,

    We will implement the modification into the next design. 


    We conducted some testing to measure the power consumption of the motor using two different drivers:

    1. The driver used by the manufacturer (XCR-E driver).
    2. DRV8311 driver

    This was our setup:

    Power Supply --> Driver --> 3-Phase A-meter --> Motor

    The results indicate that the power delivered to the motor is approximately 220mW with both drivers, confirming that the power output is correct. However, this also suggests that there are significant losses within the DRV8311 driver itself. At the moment, we do not know the exact amount of power being dissipated in the driver, and this will require further measurement.

    Our device is powered by a single-cell Li-ion battery. The 3.3V LDO output from the driver is also used to power the rest of the board, which has an idle current of around 23mA.

    We are asking whether our input voltage to the driver is too low for efficient operation. Specifically, could using a higher voltage reduce losses in the driver and, consequently, decrease heat dissipation?

    Additionally, we are considering testing another driver and are currently deciding between two models: DRV8305-Q1EVM and DRV8305EVM. Which one would be more suitable for our low-power application?

    With kind regards, 
    Radomir

  • 0 in reply to Radomir Pans
    TI__Expert 6491 points

    Hi Radomir, 

    Thank you for the additional info, and keep me updated on the outcome of these implemented changes.

    Radomir Pans said:
    We are asking whether our input voltage to the driver is too low for efficient operation. Specifically, could using a higher voltage reduce losses in the driver and, consequently, decrease heat dissipation?

    Operating the device below 6V can lead to larger RdsOn values and higher losses, as detailed in this datasheet table: 

    Further performance of the DRV8311 across voltage/temperature is shown in section 7.8 as well:

    So increasing the device operation may have a significant impact on performance as speculated-- Can you try increasing the input voltage to 6+ volts and observing the new thermal performance and current draws?

    Radomir Pans said:
    Additionally, we are considering testing another driver and are currently deciding between two models: DRV8305-Q1EVM and DRV8305EVM. Which one would be more suitable for our low-power application?

    The Q1-variant of our DRV BLDC devices are for automotive-grade requirements and applications (certified), while the regular device is typically for industrial use. There are many practical differences and I would recommend the DRV8305EVM if not designing for an automotive application.

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    Prodigy 90 points

    HI Joshua, 

    Thanks for looking into it.     I will try to perform the tests this week, I will keep you posted. 

    With kind regards,
    Radomir Pans

  • 0 in reply to Radomir Pans
    TI__Expert 6491 points

    Hi Radomir, 

    Thanks, and looking forward to hearing the results.

    Best Regards, 

    -Joshua