Hi,
This is my schematic. I use 4 wire temperature measurement with 3.3V supply on ADS1248. Connection with ADS1248 is established successfully and I am able to read/write register etc.
For the test purpose I connected 120ohm resistor and make 4 leads out of it. I am using RTD#1 together with 5k REFP0. On the actual schema I've switched P1 and N0 because it was a mistake to connect it this way.
I've set:
PGA = 32, VREF = onboard(2.048V), 5SPS, Burnout Off, Positive input A0, negative input A1, IDAC 250u
According to my calculation the input differential voltage(between AINP and AINN) should be Vin = IDAC*RTD = 250u*120OHM = 30mV. Modulator input is therefore 30mV*PGA = 30mV*32 = 0.96V. And my output should be then (0.96V/2.048)*2^24 = 7864320, and my MSB is then F0. However ADS1248 after sending RDATA command sends 3B as MSB and the value is constant. LSB is ofc changing a little. I've measured the onboard reference and it is 2.048V.
Thank you for your help.