SH7040 Datasheet, PDF (621/923 Pages) Renesas Technology Corp – Renesas 32-Bit Single-Chip RISC Microprocessor SuperH RISC engine Family/SH7040 Series(CPU Core SH-2)

16.6 A/D Conversion Precision Definitions
The medium-speed A/D converter converts analog values input from analog input channels to 10-
bit digital values by comparing them with an analog reference voltage. In this operation, the
absolute precision of the A/D conversion (i.e. the deviation between the input analog value and the
output digital value) includes the following kinds of error.
(1) Offset error
(2) Full-scale error
(3) Quantization error
(4) Nonlinearity error
The above four kinds of error are described below with reference to figure 16.7. For the sake of
clarity, this figure shows 3-bit medium-speed A/D conversion rather than 10-bit medium-speed
A/D conversion. Offset error (see figure 16.7 (1)) is the deviation between the actual A/D
conversion characteristic and the ideal A/D conversion characteristic when the digital output value
changes from the minimum value (zero voltage) of 0000000000 (000 in the figure) to 0000000001
(001 in the figure ). Full-scale error (see figure 16.7 (2)) is the deviation between the actual A/D
conversion characteristic and the ideal A/D conversion characteristic when the digital output value
changes from 1111111110 (110 in the figure) to the maximum value (full-scale voltage) of
111111111 (111 in the figure). Quantization error is the deviation inherent in the medium-speed
A/D converter, given by 1/2 LSB (see figure 16.7 (3)). Nonlinearity error is the deviation between
the actual A/D conversion characteristic and the ideal A/D conversion characteristic from zero
voltage to full-scale voltage (see figure 16.7 (4)). This does not include offset error, full-scale
error, and quantization error.
Digital output
Digital output
(2) Full-scale error
Ideal A/D conversion
111
Characteristic
110
101
100
011
010
(3) Quantization error
001
000
0
1/8 2/8 3/8 4/8 5/8 6/8 7/8 FS
Analog input
voltage
FS : Full-scale voltage
Ideal A/D conversion
Characteristic
(4) Nonlinearity error
Actual A/D conversion
characteristic
(1) Offset error
FS
Analog input
voltage
Figure 16.7 A/D Conversion Precision Definitions
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