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PGA308: Calibration details

Oba
Genius 17335 points
Part Number: PGA308
Other Parts Discussed in Thread: , PGA309

Hello

My customer has some questions about PGA308EVM software.
They are reading ppt file in PGA308EVM Video Quick-Start User Guide (part 2)(sbfc033).

Q1) Offset adjustment in page 824 of the ppt file.
I think this process is trying to minimize the offset value.
Does this process try to adjust both Course offset and ZERO_DAC(Fine_offset)?

Q2) Offset adjustment in page 826.
At final fine adjustment stage, are both Fine_Gain and Output_Amp calculated? 

Q3) Gain adjustment in page 825
It says “The output is used to back-calculate the PGA308 input (i.e. divide by gain and account for offset).”.
What is FE_Gain value for this divide calculation?

Regards,
Oba

  • 0
    Guru 140200 points

    Hi Oba,

    can you give a link to the ppt file?

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 55466 points

    Hi Oba,

    The attached document details the calibration procedure used to calibrate offset and gain on the PGA309.

    The PGA309 core amplifier is similar to the PGA308.  There are some differences between the PGA308 and PGA309:  the PGA309 uses an external EEPROM, it also adds over temperature calibration and linearization of the sensor; there are also some differences in the Gain settings available and the internal DAC ranges of the device. 

    However, the transfer function of the PGA308 and PGA309 and the calibration algorithm for course offset, fine offset, and selected gains is the same.  Below is the PGA308/PGA309 transfer function dependent on the coarse/fine offset DAC settings, input/output stage gain settings and Gain DAC settings:

    Please refer to the attached pdf document which details how the gain settings, offset DAC settings are calculated on the algorithm as the minimum and maximum pressure signals are applied during the calibration process.  Step 13 on the attached document does not apply to the PGA308, since the PGA308 does not incorporate a temperature look up table.

    PGA309_calibration_procedure (3).pdf

    Thank you and Regards,

    Luis