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DRV8323R: high temperature

Annie Liu
Genius 10295 points
Part Number: DRV8323R

Hi Team,

Compared with DRV8323RS, the temperature of DRV8323RH during operation is higher than 20℃, and the maximum detection temperature is 75℃. 

Schematic diagram designed according to the manual. The code is modified based on the previous control of DRV8323RS, and only controls the enable and PWM control pins. 

The fet is ‎TPH2R506PL, the power supply voltage is 24V.

Thanks,

Annie

  • 0
    TI__Expert 3535 points

    Hi Annie,

    Can you please clarify what your question is? The operating ambient temperature for this device is -40C to 125C.

    I can provide a full schematic review, however I'll need you to provide the power stage + the IDRIVE setting you're using. 

    Thanks,

    Michael

  • 0 in reply to Michael Arrant
    TI__Genius 10295 points

    Hi Michael,

    Is it normal for the chip to heat up to about 75°C?

    IDRIVE = Tied to DVDD

    Rated power is about 200W

    Thanks,

    Annie

  • 0 in reply to Annie Liu
    TI__Expert 3535 points

    Hi Annie,

    Is this test being ran at room temp? I tested this today on one of our EVMs with a thermal imaging camera and I saw the device heat up to about 33°C. The IC will heat up to higher temps depending on how many layers the board is, size of the board, and other layout related qualities. 

    Have they tried swapping DRV's to see if this happens to another IC? Is the DRV functioning properly? 

    Can you tell me a little more about the application the customer is using our device for?

    Regards,

    Michael

  • 0 in reply to Michael Arrant
    TI__Genius 10295 points

    Hi Michael,

    • Was tested at room temperature
    • Tried to replace the IC but still heat
    • The chip can work normally
    • The layout and routing follow the requirements of the chip manual
    • Double-layer board, circle with a diameter of 60mm

    The application scenario is to control the PMSM motor, referring to the motor FOC drive design of MIT mini cheetah

    Thanks,

    Annie

  • 0 in reply to Annie Liu
    TI__Expert 3535 points

    Hi Annie,

    OK so no affect to functionality, they can still get the motor to spin and they just want to know why it's heating up to 75C. This could be the result of a non ideal layout, has the customer reviewed our layout best practices guide? I can help review the layout if the customer would like.

    What is the temp of the IC when the motor is not spinning but still powered up?

    Regards,

    Michael

  • 0 in reply to Michael Arrant
    TI__Genius 10295 points

    Hi Michael,

    Yes, customer would like to know why the DRV8323RH chip rises to such a high temperature? Will it affect the use of the chip and will it be more easily damaged? The layout refers to the design manual. DRV8323RS uses the same layout and does not heat up.

    It's just that the IC will not heat up when it is not working. When the IC is working, the motor does not rotate, and the chip will quickly heat up to 70°C+.

    Thanks,

    Annie

  • 0 in reply to Annie Liu
    TI__Expert 3535 points

    Hi Annie,

    First I want to note that 75C is well within the operating temperature of the device. The device can operate between -40C to 125C continuously. 

    Some additional current is being drawn somewhere, resulting in the device heating up to 75C. We just need to figure out what part of the device is drawing this additional current.

    Let's start with the IDRIVE setting. We ask customers to design the rise and fall times of their FETS to be between ~100ns-200ns. 

    The FETS that you are using have a Qgd of 11nC. This alongside the max IDRIVE setting results in a rise time of 11ns. So I'm recommending that the use an IDRIVE strength between 50mA and 100mA.

    Rise time can be calculated with: Risetime = Qgd/IDRIVE strength 

    Let's check some of the power dissipation points of the device.

    How much current is Vin drawing on the hardware variant vs the SPI variant? 

    Take a look at the charge pump for each device, do you notice a significant difference? 

    What about the buck regulator, can you check the SW pin and compare the current output? Can you check DVDD output current too?

    After you check these things, and adjust the IDRIVE, I can further help you debug.

    Regards,

    Michael