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PGA309 Linearity DAC: Modelling & Choosing Value?

Andrew Meier
Prodigy 70 points

Other Parts Discussed in Thread: PGA309

The linearity DAC is sampled from the PGA309 voltage output and modifies the bridge sensor excitation Vexc.

These slight changes in Vexc, in turn, are reflected in the PGA309 voltage output.

This creates a problem when trying to model the effect of the Linearity DAC setting in a spreadsheet, because the spreadsheet software sees a circular reference between Vexc and the final voltage output.  Is there a convenient and reliable way to model the effect of the Linearity DAC setting on the final voltage output of the PGA309?

What is the best method for choosing and modelling the Lin DAC value?

  • 0
    TI__Mastermind 27715 points

    Hello Andrew,

    The PGA309 User's Guide contains an entire section (2.6 - Linearization Function) dedicated to the linearization function which gives the design equations, tables of values for typical applications, and several examples which should help clarify this for you. 

    As for modeling the effect of the LinDAC without creating a circular reference, the 'Generate_Sim_Values.xls' spreadsheet does that for you.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog and Sensing Products