RL78/G15 CHAPTER 10 A/D CONVERTER
R01UH0959EJ0110 Rev.1.10 Page 339 of 765
Mar 7, 2023
10.8.3 Quantization error
When analog values are converted to digital values, a ±1/2LSB error naturally occurs. In an A/D converter, an analog
input voltage in a range of ±1/2LSB 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, integral linearity error,
and differential linearity error in the characteristics table.
Figure 10-16. Overall Error
Ideal line
Overall error
1……1
0……0
0 V
DD
Analog input
Digital output
Figure 10-17. Quantization Error
Quantization
error
1……1
0……0
0 V
DD
Analog input
Digital output
1/2LSB
1/2LSB
10.8.4 Zero-scale error
This shows the difference between the actual measurement value of the analog input voltage and the theoretical value
(1/2LSB) 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 (3/2LSB) when the digital output changes from 0……001 to 0……010.
10.8.5 Full-scale error
This shows the difference between the actual measurement value of the analog input voltage and the theoretical value
(Full-scale – 3/2LSB) when the digital output changes from 1......110 to 1......111.
10.8.6 Integral linearity error
This shows the degree to which the conversion characteristics deviate from the ideal linear relationship. It expresses the
maximum value of the difference between the actual measurement value and the ideal straight line when the zero-scale
error and full-scale error are 0.
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