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TMS320F2800157: F2800157 interface with different gate driver how to calculate Full scale current ?

Prabhakaran CP
Prodigy 20 points
Part Number: TMS320F2800157
Other Parts Discussed in Thread: DRV8353

Tool/software:

Hi,
We are working on a custom board with F2800157 MCU. Same MCU Launchpad with DRV8353 we can run the motor smoothly at various speeds.
But when we moved the code verified code to the custom board, the motor ran for a few minutes and got stopped by the module due to the current error.

1)in the custom board we not using a DRV8353 Chip instead of using an IRF2286 gate driver Is the doubt in the calculation of full-scale current and voltage?
The full-scale voltage we calculated based on the divider resistor but we Full-scale current we don't know for because in DRV8353 using current gain we set
various full-scale current values here no way to adjust the current gain and the current shunt is 0.3 ohm.

As per 0.3 ohms if calculated I got the value as 110 but not sure about the gain in IRF but the gain is adjustable in DRV .How to calculate for IRF ?

  2) If some random values for USER_M1_ADC_FULL_SCALE_CURRENT_A behaviors are different motor running for some time and getting the module over the current fault. finally motor stopped.

     

3) The motor running at 50ns dead band at Build_Level2 without issues, but, the same deadband motor not running at BL#3 and BL#4 . The motor only runs if we set 4000 to 5000  deadband.

Kindly help us, we are sure there are some calculation issues with ADC Full-scale current values.

Appreciate your help asap. 

Thanks 

Prabhakaran

  • 0
    TI__Expert 7771 points

    Prabhakaran,

    ADC_FULL_SCALE_CURRENT and ADC_FULL_SCALE_VOLTAGE parameters have a specific physical definition. If you have an ADC channel that's measuring current, then a value of 0xFFF (the highest possible value for a 12-bit ADC), the current being measured is at ADC_FULL_SCALE_CURRENT Amps. The value of ADC_FULL_SCALE_CURRENT is dependent on your physical circuit and the information provided by the datasheet for your gate driver.

    Let me know if this helps.

    Regards,
    Jason Osborn

  • +1 in reply to Jason Osborn
    Prodigy 20 points

    Hello ,

    Thanks for your Response.

    Checked as per you suggestion,Shunt resistor is 0.3 milli Ohms ,finally we got below values like this (attached screenshot) for USER_M1_ADC_FULL_SCALE_CURRENT_A = "864.8854.."

    But if we applied the same value in UMC code .Motor is not running and always getting Module Over Current Fault.Instead of this calculated if applied very less value to USER_M1_ADC_FULL_SCALE_CURRENT_A less than "2.0 or 0.5" .Motor running for long time(48min ) running without issues then later its getting module over current error.

    if we keep reduce USER_M1_ADC_FULL_SCALE_CURRENT_A value lesser than 0.5 then motor running time getting extended .so,motor performance is inverse of the above calculation of USER_M1_ADC_FULL_SCALE_CURRENT_A.

    Thanks for your  support.

    Regards

    Prabhakaran

  • +1 in reply to Prabhakaran CP
    TI__Expert 7771 points

    Prabhakaran,

    Apologies for the delay in response. I've been looking into this, and I cannot find a reason for the behavior you're seeing. Please do the following to assist with further debugging:

    • Determine what, if any, changes have been made to the algorithm
    • Model the circuit in a SPICE program, such as TI-TINA, to determine what current corresponds to a reading of 3.3V output.
    • While running the motor, put a current probe on one of the motor phases. What is the actual current running through the motor?

    Regards,
    Jason Osborn