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8XC196MC, MD, MH USER’S MANUAL
12-16
Figure 12-10. Actual and Ideal A/D Conversion Characteristics
The actual characteristic of a hypothetical 3-bit converter is not perfect. When the ideal charac-
teristic is overlaid with the actual characteristic, the actual converter is seen to exhibit errors in
the locations of the first and final code transitions and in code widths, as shown in Figure 12-10.
The deviation of the first code transition from ideal is called zero-offset error, and the deviation
of the final code transition from ideal is full-scale error. The deviation of a code width from ideal
causes two types of errors: differential nonlinearity and nonlinearity. Differential nonlinearity is
a measure of local code-width error, whereas nonlinearity is a measure of overall code-transition
error.
FULL SCALE ERROR
ZERO OFFSET
ACTUAL
CHARACTERISTIC
1/2123456786 1/2
0
1
2
3
4
5
6
7
INPUT VOLTAGE (LSBs)
Ø OUTPUT CODE, Q
ABSOLUTE ERROR
IDEAL
CHARACTERISTIC
A0084-01