I am using a AD7682 A/D in a very simple design. We have 4 prototypes build, on 4 of them, the output result from the A/D on a tie to ground input is near 0 as anticipated, only the bit 0 change from time to time, but not more. On one board, the output count is near 30 with the same condition, we check everything, even replace the chip, this only lower the count to 20, but still high. The A/D is working anyway, the only problem is the fact that all reading are offset by the error count.
Any suggestion on how to correct this, or why this append?