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I Total value with DRV8301 kit

KV
Expert 1800 points
Other Parts Discussed in Thread: DRV8301

Hi,

I am experimenting with DRV8301 kit and would desire to know the total current - "I_TOTAL" value.  This is connected to ADC-A2 and used the below statement to read the register

Totalcurrent=AdcResult.ADCRESULT7;

The watch window value displays 0.499 (IQ12 format) and the motor is under no load.  The current drawn would be very less.  The DRV_gain is set to 40 i.e., base current 20.625 Amps. 

Could I know what the watch window value indicates?.

thx

 

  • 0
    TI__Guru** 119560 points

    recall that your ADC is 0-3.3V while your motor current/voltage sampling is in a range of -X to +X

    So what you want to do is scale the inputs where 1.65V ADC input is equivalent to 0, 0V is -X and 3.3V is +X.

  • 0 in reply to ChrisClearman
    Expert 1800 points

    Thanks Chris.  The DRV8301 board is designed for 60 amps peak output current per phase.  Looks like the Opamp is doing summing of voltages across phases.  Could I assume 0, 1.65V, 3.3V to be the output of the opamp for -60A, 0A , 60A.  So accordingly I could scale the inputs.  Please suggest.

    thx

  • 0 in reply to KV
    TI__Guru** 119560 points

    BLDC_Int-Settings.h

    line 105

    or PM_Sensorless-Settings.h

    line 98

    #elif DRV_GAIN == 40
    #define BASE_CURRENT 20.625  // Base peak phase current (amp) , maximum measurable peak current (with DRV830x gain set to 40)