BOOSTXL-DRV8305EVM: The problem of positive and negative feedback of FOC current op amp

Green Deng

Dear team:

One of my customers changed the MOSFET pre-driver chip and op amp chip on the basis of BOOSTXL-DRV8305EVM. When running the lab_02b program, the current will be very large and the motor will also be stuck. So he has the following questions:

1, The op amp he used in his circuit board design is a positive feedback op amp, so besides modifying the void HAL_updateAdcBias function in the code, which function needs to be modified? How to modify?

2, In addition to modifying the positive and negative feedback of the op amp, the op amp multiple, and the voltage feedback, what parameters need to be modified in the software?

Best regards

over 3 years ago

+1 Aaron Barrera over 3 years ago

TI__Mastermind 26046 points

Hello,

Thanks for posting to the MD fourm!

1) Please check for a function called HAL_readADCDataWithOffsets() in hal.h. There should be two lines of code called HAL_getCurrentScaleFactor(handle) that calculates the current and voltage scale factors. If you add a negative sign in front of it, it can be used for OpAmps with positive feedback.

static inline void
HAL_readADCDataWithOffsets(HAL_Handle handle, HAL_ADCData_t *pADCData)
{
    HAL_Obj *obj = (HAL_Obj *)handle;

    float32_t value;

    float32_t current_sf = HAL_getCurrentScaleFactor(handle); //negative feedback = positive sign
    float32_t voltage_sf = HAL_getVoltageScaleFactor(handle);
    
    ...
    
}

2) I am not sure by heart on every parameter that needs to be changed, but you can refer to this post from the C2000 team that shows how to modify the HAL layer for new hardware: https://e2e.ti.com/support/microcontrollers/c2000/f/c2000-microcontrollers-forum/987190/c2000ware-motorcontrol-sdk-using-other-adc-for-motor-current-measurements

Which MCU hardware are you using?

Thanks,
Aaron

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BOOSTXL-DRV8305EVM: The problem of positive and negative feedback of FOC current op amp