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ADS1246: ADS1246 with 3.3V AVDD

Leo Marrero89
Prodigy 70 points
Part Number: ADS1246
Other Parts Discussed in Thread: ADS1230, ADS1232, ADS1231, ADS1220, ADS1235, ADS124S06

Hi Everyone, 

I am planning to use the AD1246 with a load cell at 3.3V operation. 

1. Can is still use the the 2.048V reference or is it better to use an external reference?

2. Is there an effect on the effective number of bits (ENOB)? Based on my computation so far, i loose dynamic range by using a 3.3V instead of 5V but is the ENOB still the same? Based on the datasheet, the ENOB is only affected by the reference voltage. However, according to this application note SBAA184, i need more bits due to the difference in the full scale range and the dynamic range of the loadcell input. 

Thanks,

  • 0
    TI__Mastermind 49041 points
    Hi Leo,

    Thanks for your post and welcome to the forum!

    If you take a look at the Device Comparison Table, you will see that the ADS1246 does not have an internal reference. Unfortunately this means that the ADS1246 is not ideal for load cell applications since the excitation voltage should be the same as the reference. For the ADS1246, the reference must be less than AVDD-1V, so the maximum reference voltage is 2.3V.

    I encourage you to explore a few other parts in the portfolio:

    The highest precision devices for load cell applications while still being relatively low cost are the:
    ADS1230 (20-bit)
    ADS1232 (24-bit)
    ADS1231 (24-bit)

    Higher cost and higher speed would be:
    ADS1220
    ADS1235
    ADS124S06

    There are advantages/disadvantages to each one. The top group is precision at the sacrifice of speed (max of 80sps) but are very simple to operate as well (no registers and pin controlled only.)
  • 0 in reply to Alexander Smith
    Prodigy 70 points

    Thanks for the feedback, Alexander!

    Looks like I will have to rethink my setup a bit and look at the others. Thank you for the recommendations. 

    Leo