SH7205 Datasheet, PDF (1086/1904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 21 A/D Converter (ADC)
21.6 Definitions of A/D Conversion Accuracy
The A/D converter compares an analog value input from an analog input channel with its analog
reference value and converts it to 10-bit digital data. The absolute accuracy of this A/D conversion
is the deviation between the input analog value and the output digital value. It includes the
following errors:
• Offset error
• Full-scale error
• Quantization error
• Nonlinearity error
These four error quantities are explained below with reference to figure 21.7. In the figure, the 10-
bit A/D converter is illustrated as the 3-bit A/D converter for explanation. Offset error is the
deviation between actual and ideal A/D conversion characteristics when the digital output value
changes from the minimum (zero voltage) B'0000000000 (000 in the figure) to B'000000001 (001
in the figure)(figure 21.7, item (1)). Full-scale error is the deviation between actual and ideal A/D
conversion characteristics when the digital output value changes from B'1111111110 (110 in the
figure) to the maximum B'1111111111 (111 in the figure)(figure 21.7, item (2)). Quantization
error is the intrinsic error of the A/D converter and is expressed as 1/2 LSB (figure 21.7, item (3)).
Nonlinearity error is the deviation between actual and ideal A/D conversion characteristics
between zero voltage and full-scale voltage (figure 21.7, item (4)). Note that it does not include
offset, full-scale, or quantization error.
Digital output
Digital output
(2) Full-scale error
Ideal A/D
111
conversion
characteristic
110
101
100
011
010
(3) Quantization
error
001
0000 _{1 2}
10241024
[Legend]
FS: Full-scale voltage
10221023 ^FS
10241024 Analog input
voltage
Ideal A/D
conversion
characteristic
(4) Nonlinearity
error
Actual A/D
convertion
characteristic
(1) Offset error
FS
Analog input
voltage
Figure 21.7 Definitions of A/D Conversion Accuracy
Rev. 1.00 Mar. 25, 2008 Page 1054 of 1868
REJ09B0372-0100