HD6417706 Datasheet, PDF (556/709 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer Super RISC engine Family/SH7700 Series

19.8 Definitions of A/D Conversion Accuracy
The A/D converter compares an analog value input from an analog input channel to its analog
reference value and converts it into 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 using figure 19.10. 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) 0000000000 (000 in the figure) to
000000001 (001 in the figure) (figure 19.10, item (1)). Full-scale error is the deviation between
actual and ideal A/D conversion characteristics when the digital output value changes from the
1111111110 (110 in the figure) to the maximum 1111111111 (111 in the figure) (figure 19.10,
item (2)). Quantization error is the intrinsic error of the A/D converter and is expressed as 1/2 LSB
(figure 19.10, item (3)). Nonlinearity error is the deviation between actual and ideal A/D
conversion characteristics between zero voltage and full-scale voltage (figure 19.10, item (4)).
Note that it does not include offset, full-scale or quantization error.
Digital output
111
110
Ideal A/D
conversion
characteristics
Digital output
Ideal A/D
conversion
characteristics
(2) Full-scale error
101
100
(4) Nonlinearity
011
error
010
(3) Quantization
error
001
000
0 1/8 2/8 3/8 4/8 5/8 6/8 7/8 FS
Analog input
FS: Full-scale voltage
voltage
Actual A/D
convertion
characteristics
(1) Offset error
FS
Analog input
voltage
Figure 19.10 Definitions of A/D Conversion Accuracy
Rev. 4.00, 03/04, page 510 of 660