Hello Rolando,
Thanks for posting some interesting questions on TMP121.
Sorry about the confusion in the datasheet. TMP121/122/123/124/125 are based out of the same silicon die and confirmation bit on Page 6 of the data sheet refers to device confirmation. I checked the design files and when this bit is '0' it refers to TMP121/TMP123 ('1' refers to TMP122/TMP124) . It doesn't signify data valid or data ready functionality. So in your case you should be able to read this bit as '0'.
Table 2 deals with the binary equivalence of the temperature value for the customer to decode. It's not describing the register values it is only dealing with the binary equivalent temperature and hence doesn't include the confirmation bit.
The largest change from sample to sample really depends on the temperature range and its rate of change in your application. Once I understand the range, I would add a guard band of max accuracy error (2deg C) + an additional 1-2degree just to be on the safe side while filtering out the unwanted invalid values.
I would also check and make sure the code that decodes the temperature register is correct because you are getting double or half of the actual temperature values some time. Speed should not be an issue in your case and data output from the internal shift-register is also buffered so this cannot be a synchronization issue with SPI click and internal oscillator clock.
I hope this help and do let me know how it goes.
Best Regards,
Abhi Muppiri
Applications Engineer
MHR- Sensing Products
Texas Instruments
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