543
Chapter 15
A/D Converter
Preliminary User’s Manual U15839EE1V0UM00
(3)
Quantization Error
When analog values are converted to digital values, a
±
1/2 LSB error naturally occurs. In an A/D
converter, an analog input voltage in a range of
±
1/2 LSB is converted to the same digital code, so
a quantization error cannot be avoided.
Note that the quantization error is not included in the overall error, zero scale error, full scale error
and non-linearity error in the characteristics table.
Figure 15-15:
Quantization Error
(4)
Zero-scale error
This shows the difference between the actual measurement value of the analog input voltage and
the theoretical value (1/2 LSB) when the digital output changes from 0...000 to 0...001. If the
actual measurement value is greater than the theoretical value, it shows the difference between
the actual measurement value of the analog input voltage and the theoretical value (3/2 LSB)
when the digital output changes from 0...000 to 0...010.
Figure 15-16:
Zero-Scale Error
0.......0
1.......1
Digital output
Quantization error
1/2LSB
1/2LSB
Analog input
AV
REF
0
111
011
010
001
Zero-scale error
Ideal line
000
0
1
2
3
AV
REF
Digital output (Lo
w
er order 3 bits)
Analog input (LSB)
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