ADS1248: ADS1248 drawing problem with pt100 and pressure transmitter

Hi Michael Soldierram,

What do you think is the issue with this drawing?

You might consider adding a pull-up on the RESET pin to ensure the device starts up in a known state

You also don't need C25, C27, or R13, since that node is tied directly to ground anyway.

-Bryan

Hi Michael Soldierram,

The RTD input looks fine. You might need to change the component values in the filter, but that can be done experimentally once you get your prototypes since those resistors/caps are easy to change. See here for some general recommendations: https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/955466/faq-delta-sigma-adc-anti-aliasing-filter-component-selection

I am not sure what you are trying to do with the pressure input - is that for a 4-20mA output pressure sensor? I see a 100ohm resistor and a single-ended measurement between AIN2 and AIN3. Note that the ADS1248 cannot make single-ended measurements with a unipolar supply, see equation 5 in the datasheet

-Bryan

Hi Michael Soldierram,

You would just need to use two resistors in series (maybe 3x), and then measure across the top (or middle) resistor. Again, you should perform the calculations to determine if your input signals meet the PGA common-mode range, as described in equation 5 as well as section 9.3.2.1.

Alternatively, you could consider using the ADS124S08, which is the next-generation version of the ADS1248. The ADS124S08 has more features, more input channels, lower power, lower noise, higher sampling rates, and additionally allows for single-ended inputs by disabling the PGA. Therefore, the implementation will be simpler, and basically your same schematic can be used

-Bryan