There is a huge apparent bit of confusion and inconsistency related to the term of LSB's when it comes to the discussion of A/D converters and their performance factors.

Some folks seem to think that an error of +/- 1 LSB means to throw away the low bit by masking it off. The same such folks seem to think that an error of +/- 3 LSB means to chop off the three low bits.

This is not what virtually all A/D specifications actually mean by "so many LSB's of error". A single LSB is meant to refer the magnitude of the input analogue signal that causes the A/D converter to change its reported conversion count by one in total value. (For example an 8-bit A/D converter operating over a 0 to 5V range has an LSB value of about 19.5 mV. So if the A/D converter is spec'ed at linearity error of +/- 3 LSBs it means that the linearity is +/- 19.5 x 3 = 58.6 mV. It is not meaning to throw away the low three bits which would correspond to an error of 2^^3 or 8 LSB's.

Michael Karas