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PGA305: PGA305 P_GAIN vs PADC Gain

Lori Ferger52
Intellectual 495 points
Part Number: PGA305


Document SLDS231 has a schematic on page 1 showing a simplified block diagram of the PGA305.  The "Resistive Sensing AFE" shows a PGA feeding the 24-bit ADC. 

- Is "P_GAIN", as referenced in the PGA305 EVM GUI on the "EEPROM Config-Analog" page,  the gain of the this PGA which feeds the ADC. 

- Is PADC_Gain, as referenced in the PGA305 EVM GUI on the "EEPROM Config-Digital" page, applied after the ADC conversion?

- The "Analog PADC Data" on the PGA305 EVM GUI on the "EEPROM Config-Analog" page does not seem to change value if P_GAIN is changed.  Is this data always returned with a gain of "1"?

  • 0
    TI__Mastermind 31655 points

    Hello Lori,

    P_GAIN is the gain of the PGA in front of the Pressure ADC.

    PADC_GAIN is a digital gain applied after the ADC conversion.

    When you change the P_GAIN on the EEPROM Config-Analog page it only writes the corresponding EEPROM register. The actual P_GAIN will not update until the compensation engine has been run. To see a change to the PADC data on the EEPROM Config-Analog page you will need to either run the compensation engine then switch back to digital interface mode after changing P_GAIN on that page, or you can go to the ADC settings page and change the P_GAIN there (this changes the control register for the P_GAIN directly).

    Regards,