SH7206 Datasheet, PDF (881/1188 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 17 A/D Converter (ADC)
17.6 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 17.7. In the figure, the 10
bits of the A/D converter have been simplified to 3 bits. 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 17.7, 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 17.7, item (2)). Quantization
error is the intrinsic error of the A/D converter and is expressed as 1/2 LSB (figure 17.7, item (3)).
Nonlinearity error is the deviation between actual and ideal A/D conversion characteristics
between zero voltage and full-scale voltage (figure 17.7, 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
110
characteristic
101
100
011
010
(3) Quantization
error
001
000
01 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 17.7 Definitions of A/D Conversion Accuracy
Rev. 3.00 Jun. 18, 2008 Page 857 of 1160
REJ09B0191-0300