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ADS41B49 data plots

Dan LaChance
Expert 1770 points
Other Parts Discussed in Thread: ADS41B49

Hello TI,

My customer is considering using the ADS41B49 A/D converter on an upcoming design.  He is skeptical about some of the data in the datasheet. 

Specifically, he's hoping that the 12-bit data/plots are accurate, but were erroneously copied over to the 14-bit plot pages, and that the 14-bit performance is actually better than shown.  The reasoning is that figures 17 and 19 look virtually identical to figures 35 and 37, but they represent SFDR for a 12-bit and 14-bit converter, so he's expect the 14-bit to be appreciably better.

The data sheet to reference is the SBAS486E – NOVEMBER 2009–REVISED JULY 2012.

Thanks,

Dan

  • 0
    TI__Genius 17320 points
    Hi Dan,

    This is not a typo - well at least one that I'm aware of. The data is accurate. The SFDR is not limited by the resolution of the ADC, but rather the linearity of the sample and hold and input buffer. Take a look at the electrical tables where you can easily compare the SFDR between the 12-bit and 14-bit versions (page 4 of the datasheet). You'll see that the typical SFDR performance is exactly the same. The SFDR will be limited by HD2 or HD3 at large input levels.

    Note that the number of bits has a direct effect on noise, but not on distortion. We would not expect the 12-bit ADC to have reduced SFDR performance, just reduced SNR performance. The 14-bit version may show slightly better SFDR at low input levels. See figures 22 and 39.

    Regards,
    Matt Guibord