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PGA305EVM-034: DAC calibrations and 3P-1T reading

Renan Santos Adriano
Mastermind 22260 points

Part Number: PGA305EVM-034

Hello Team,

My customer is trying to perform a calibration according to the attached data, however he was not successful.

data_calibration.zip

They did the DAC calibrations and 3P-1T reading, but when they are going to do the DAC readings it corresponds to the sensor reading, the fixed output is fixed at 0.34V. Where there should be a variation from 2.00 to 6.00V, according to the DAC calibration.

What could be wrong with this procedure?

Regards,

Renan

  • 0
    TI__Mastermind 31655 points

    Hello Renan,

    This is most likely due to an EEPROM CRC error or a diagnostic trigger. When the EEPROM CRC in the last byte of the EEPROM does not match the value calculated based on the entire EEPROM space the DAC output will be forced to a user-defined value (on the EEPROM digital page in the GUI). This could also be a result of one of the analog diagnostics. For now I would disable all of the diagnostics and double check that the correct CRC value is being used. Once all of the coefficients are written and any other EEPROM changes are made, they can use the GUI to calculate a new CRC value and write it to the EEPROM. 

    Regards,

  • 0 in reply to Scott Cummins
    TI__Mastermind 22260 points

    Hello Scott,

    My customer already did the tests, and checked the CRC, where they calculated and recorded it again. The output of the DAC continues with a fixed value. What else they could do?

    They also have another question, on the ADC_Settings screen, when they read the ADC (Pressure Sensor), is this value already offsetting the values from the coefficients and scale factors?

    Regards,

    Renan

  • 0 in reply to Renan Santos Adriano
    TI__Mastermind 31655 points

    Hi Renan,

    The ADC data read from the PADC registers is raw data with no digital offset or linearization from the coefficients applied. Has the customer been testing the compensated output in compensation mode? If the PGA305 is in digital interface mode, the output will not be controlled relative to the ADC input. After the EEPROM has been configured, the PGA305 should either be power cycled, or put into compensation mode through the GUI.


    Regards,

  • 0 in reply to Scott Cummins
    TI__Mastermind 22260 points

    Hello Scott,

    My customer did the test again, and the result was the same.
    In the PGA305 GUI user manual, on page 103 we have the Calibration Demo, but in the GUI they are using (version 1.6.1.0) it doesn't have this option. Is it possible that I am using the wrong version? Would it be possible to send me the version with this option?

    Regrds,

    Renan

  • 0 in reply to Renan Santos Adriano
    TI__Mastermind 31655 points

    Hello Renan,

    The GUI version available on the web is the latest version. Can your customer please provide their full EEPROM contents in the most recent configuration?

    And it wasn't entirely clear. Has the customer tried disabling the diagnostics and masking all of the AFEDIAG bits? They can also more easily tell if they are encountering a diagnostic or CRC fault by configuring the Fault Configurable Value to a specific setting to see if the fixed output changes to that value.


    Regards,

  • 0 in reply to Scott Cummins
    TI__Mastermind 22260 points

    Hello Scott,

    Please see attached file provided by my customer:

    result.zip

    The DAC output is not working. The output voltage is 0 volts.

    Regards,

    Renan

  • 0 in reply to Renan Santos Adriano
    TI__Mastermind 31655 points

    Hi Renan,

    According to the EEPROM page read from the data that you sent me, it looks like there are no coefficients programmed into the PGA305 at all. Since all of the gain coefficients are set to 0, the output will always be set to 0. To test a direct passthrough, the G0 coefficient could be set to 0x400000. This will set the gain to 1. At least one of the G-N coefficients will need to be non-zero before there will be any output at the DAC.


    Regards,