The QD4 series contains a built-in voltage reference that is better than 1% accurate. Not bad, but I have an application that could benefit from better accuracy. I am wondering if anybody has tried calibrating the reference with a trim value in software, on a chip-to-chip basis. I think this could reduce the ADC's absolute voltage measurement error by a factor of 2-3.
Our factory uses a "beehive" gang programmer. I am thinking we would need to modify it to
1) place a highly-accurate reference voltage on one of the inputs,
2) program the chip with a measurement program that can communicate a trim value back to the PC,
3) read the trim value back to the PC
4) Have the PC program each chip with a binary containing the proper trim value (probably only 10 or so values would come into play).
If anybody has suggestions on how to accomplish items 2-4, or if you know of a reason why this whole thing will never work or be beneficial, or if you've tried this yourself and succeeded, please let me know.