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PGA305EVM-034: DAC Calibration

Igor Giterman
Prodigy 145 points

Part Number: PGA305EVM-034

EVM GUI manual has section on DAC calibration.

It is not clear what DAC calibration does and why it is is needed at different temperatures and where this calibration codes are stored. 

Can somebody explain this one?

Thank you for your help.

  • 0
    TI__Guru** 113765 points

    Hi Igor,

    You want your DAC to output certain voltage (or current) values based on the pressure and temperature data at the time of calibration otherwise how would the PGA305 know what to output?  The DAC calibration values are not stored, but rather passed along with the pressure and temperature data collected at the time of the calibration as part of the coefficient computation.

    Let's say you do a 3P1T calibration.  For each of the three pressures you would want a specific DAC output.  So you would need to have a corresponding DAC output that matches the pressure.  As the DAC will have some offset and gain error, you want to set a desired DAC code and output voltage.  Then you would measure the actual DAC output voltage.  You would calculate the actual DAC code needed to set the DAC output to the desired response.  This data, along with the pressure and temperature data are then sent to the coefficient calculation algorithm in the GUI.

    Best regards,

    Bob B  

  • 0 in reply to Bob Benjamin
    Prodigy 145 points

    Hello Bob,

    Thank you for the explanation.

    In principle I think I understand the process:

    1. Collect Pressure Data at calibration points

    2. Collect Temperature Data at calibration points

    3. Collect DAC data at temperature calibration

    4. Set Matrix of Digital data of Raw Pressure Reading at Pressure and Temperature points (the Matix)

    5. Compute coefficients with "Target" of DAC Values at each temperature

    6. Load coefficients into SoC

    7. Run verification at desired Temperature and Pressure points (On "measure matrix grid" and "between points"

    Please let me know if my description of the process is correct. 

    I need to run one complete cycle to make sure I understand the complete process and correctly implement each step.

    Thank you for your help.

    Regards,

    Igor

  • 0 in reply to Igor Giterman
    TI__Guru** 113765 points

    Hi Igor,

    This process appears correct.

    Best regards,

    Bob B