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DRV8353R: Is it a Issue of DRV8353's Current Messing Signals ?

Part Number: DRV8353R

Hi,

Our Project is working now with DRV8353RS to drive a PMSM Motor. We are using all of 3 Shunt Resistors to measurement Motor Phase Currents. 

By HIL- Testing it happened a strange thing with motor current. After about 20 seconds with high load test, current value decrease about 3A.

I have checked these SO_x Signals from Gate Driver and it is probably depended on temperature. By 90 °C increases SOx_Signal 0,01V like be calculated 3A.

First question: 

How can i compensate this temperature drift effect ?

Second question: 

After this Measurement, i have noticed that, three SOx_Signals don't have the same voltage level and the signal behaviors in depending on temperature are also difference. 

Below you can see a diagram of SOx_Signal depending on temp. 

Thanks !

Best regard.

  • Hoang,

    Thanks for posting on the MD forum!

    Are you using the SPI device? If so you could re-run the calibration sequence once the board is warm and while the motor is not spinning. 

    If you are using a hardware device, you can use a temperature sensor and correct for the error using your MCU.

    Regards,

    -Adam

  • Hi Adam,

    Thanks for your answer.

    Yes, we are using SPI device. We have tried to calibrate it, but we don't know if it rights way to calibrate succeed.

    Could you please describe me, how it's procedure looks (best with step by step). What, where should I make special attention to?

    What can be happened after the calibration procedure ?  Should all of three signals have a same progression ?

    I'm still not understanding, why 3 Signals have different variation of its amplitude ? 

    Below are our measurement results with same PCB, with and without connection to MCU. 

    I have measured  on many pcbs and the results are differently, should i run the calibration procedure for every pcb (every new gate driver) ?

    Many thanks again for your Supports and I hope you can help me to solve this problem. Not exact current measurement damages our motor control system.

    Regards,

    Hoang 

      

  • Hoang,

    What is your calibration procedure?

    The calibration is not internally temperature compensated, you will need to do this with your MCU if this is needed.

    What I would recommend is calibrating at a temperature near what you expect the system to be used at. You could always re-calibrate during run-time when you know there is little or no current flowing through the bridge.

    Regards,

    -Adam

  • Hi Adam,

    I understood what you wrote, that "the calibration is not internally temperature compensated" and i want to calibrate it with our MCU too, but I don't know if we do it in the right way.

    What I got from data sheet of DRV8353x (SLVSDY6 –AUGUST 2018) are as following: In the end of this post is shown again, what are written in data sheet.

    - First I think, there is some mistake, because in the register setting, we don't have "AUTO_CAL" bit, we have only "CAL_MODE". 

      We set "CAL_MODE" from 0 to 1 to use internal auto calibration routine.

    -And then for every phase signal we set these register bits "CSA_CAL_A", "CSA_CAL_B" and "CSA_CAL_C" from 0 to 1 to rerun the auto calibration routine for each of motor phase signal. 

    Is this procedure correct ? 

    In the data sheet is written, that " During auto calibration all the amplifiers will be configured for the max gain setting in order to improve the accuracy of the calibration routine.". 

    Can you please tell me, what is happened with gain setting after the calibration ? Is it still changed with max gain setting or should be automatically changed back to what we set before ?

    Is the change of gain setting during the calibration affecting just one phase or all phases? In Our application we are using the gain setting of 20.

    Regards,

    Hoang

  • Hoang,

    AUTO_CAL should read CAL_MODE, sorry about that, this is a typo I will correct.

    Yes your procedure is correct.

    The gain setting is only changed during the calibration and it will switch back to your selected gain afterwards.

    The gain is changed for all CSA and then returned back to the setting they were previously before calibration.

    Regards,

    -Adam