This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8873-Q1: Junction temperature is exceeding 150 deg for a rms current greater than 5A

Part Number: DRV8873-Q1
Other Parts Discussed in Thread: DRV8256, DRV8245-Q1

Hi

We are using the part DRV8873-Q1 in our automotive design. The motor driver is used for controlling window up and down motion in cars. 

While calculating junction temperature using the datasheet as per section 8.2.1.2, we observed that junction temperature exceeds 150 deg for an rms current greater than 5A.

We have a requirement for continuous current of 7-8A and peak current of 10A. But 7A is exceeding the junction temperature limit of 150 deg. We have connected the motors to 12V in our design.

Please let us know if this motor driver DRV8873-Q1 is capable of driving loads of 7-8A?

If yes, why is it exceeding the max junction temperature mentioned in datasheet?

Regards

Prema

  • Hey Prema, 

    7A to 8A continuous load is at the limits of this device performance, and would likely require external heatsinking if it could maintain it.  If this is a new design, I recommend looking at DRV8243-Q1, or higher current variations DRV8244-Q1 or DRV8245-Q1

    DRV8245 can maintain 8.9A without PWM for 10 seconds, or 7.7A DC with PWM for 10 seconds:

    Or you could use the on-chip current regulation to limit the current to a lower value such as 6.5A.

  • Thanks!

    What is the maximum current the chip DRV8873-Q1 can sustain?

    We are doing a POC and we have initiated purchase of this part. Do you see any major concerns? Kindly let us know

  • Hey Prema, 

    What is the maximum current the chip DRV8873-Q1 can sustain?

    For continuous operation, this will depend on the thermal limitation of the device which is affected by the PCB layout and if you're using external heatsinks. See the app note Best Practices for Board Layout of Motor Drivers for ways to optimize the PCB layout.  

    Follow the calculations in 8.2.1.2 Drive Current and Power Dissipation of the datasheet to calculate the device temperature under a given load.  

    For momentary pulse, the device OCP will trip above 10A of current (I_OCP).  

    Just to give a ballpark answer, it looks like DRV8256 with a slightly higher 165mΩ RDS_ON can run RMS current of around 3.5A, so I would guess DRV8873-Q1 to be able to run 4A RMS continuously.  But that's just my rough guess, I recommend testing it out. 

    We are doing a POC and we have initiated purchase of this part. Do you see any major concerns?

    No major concerns! I do recommend looking into the recently released DRV8245-Q1 to (feel free to order an EVM https://www.ti.com/tool/DRV8245H-Q1EVM ) if that would work better for you. 

    Best,

    Jacob