Tool/software:
Hello,
In reference to the following forums:
FDC1004: Different capacitance value measured when CAPDAC change
FDC1004: CAPDAC Anomaly when value changes from 16 to 17
I have been trouble shooting the same issue and have seen the same anomaly as Neil Hall with a similar conclusion (although, I have occurrences at different CAPDAC values). Has there been a solution by chance?
I'm using the FDC1004 in 'single ended measurement' to read 4 different capacitive sensors while filling a container systematically in 1ml intervals (reading after each 1ml is added and liquid has settled); I've also conducted testing with only one cap sensor attached and see the issue in all scenarios. I'm keeping a low footprint so I can't add the EVM to my set-up. The data shifts down briefly between CAPDAC values 7/8 and again at 15/16 then linearly increases from that point. I can't help but notice that this occurrence seems to coincide with transitional bit values.
in section 6.3.2 of the datasheet, it's noted that the CAPDAC has a " a 5-bit resolution, monotonic transfer function" could the major bit switches for high order bits (ie. capdac switching from 0111 to 1000) be de-railing the monotonic transfer somehow?
It may help to look at capacitances of 25pF to 40pF for the first switch (CAPDAC values 7 to 8) then again 50pF to 60pF for the second (CAPDAC values 15 to 16)
I would very much appreciate your help, I'm hoping to get going on some more testing with the chip but need make sure the data is accurate first.
Cheers,
Alexandria
