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DAC8750: Total output error calculation

TKO
Prodigy 225 points

Part Number: DAC8750

Hello,

I need your help to calculate the total unadjusted error(TUE) for Iout over temperature. The TUE mentioned in the Electrical Characteristics table is +/-0.16FSR, but based on the datasheet graphs I believe the device can perform better in my application. I'm not 100% sure which graphs I need to calculate together.

In my application the output range is 4-20mA, internal reference and internal Rset are used and analog Vdd is 24V. I'm looking for a maximum error over the temperature range of -20C to +65C? For example, what kind of error I can expect to see when I program the output for 20mA?

I may need to implement calibration depending on the result. 

Thanks in advance!

  • 0
    TI__Genius 11750 points

    Howdy TKO,

    I believe Fig 17 of the DS should help shed some light on total unadjusted error vs DAC code. As you may know, TUE, can be broken down into independent error sources:

    • gain error,
    • offset error
    • Integral Non-linearity error

    The TUE data in Fig 17 displays TUE vs code. One important parameter not mentioned in your post is the BOOST configuration.  This largely affects TUE across codes as illustrated in the plot.

    Fig 19 displays the worst case TUE (without BOOST), which is shown as an absolute vale of min/max in this plot, across temp. It is not possible to predict the TUE of a DAC code using this data, as it encompasses worst case TUE across all DAC codes. With this graph, and for the temperature range described above, I can speculate the worst case TUE to be ~0.075%FSR (AVDD=10V, Rload=300).

    To help reduce output error, a simple 2pt calibration can be employed at room temp to establish the gain and offset error of your system. The datasheet does include Gain error and Offset error temperature coefficients, which can be incorporated into you calibration algorithm.

    Hope this information helps,

    Best Regards,

    Matt