M16C62_M Datasheet, PDF (454/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

A-D Converter
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
2.7.13 Absolute Accuracy and Differential Non-Linearity Error
• Absolute accuracy
Absolute accuracy is the difference between output code based on the theoretical A-D conversion
characteristics, and actual A-D conversion result. When measuring absolute accuracy, the voltage at
the middle point of the width of analog input voltage (1-LSB width), that can meet the expectation of
outputting an equal code based on the theoretical A-D conversion characteristics, is used as an ana-
log input voltage. For example, if 10-bit resolution is used and if VREF (reference voltage) = 5.12 V,
then 1-LSB width becomes 5 mV, and 0 mV, 5 mV, 10 mV, 15 mV, 20 mV, ···· are used as analog input
voltages. If analog input voltage is 25 mV, “absolute accuracy = ± 3LSB” refers to the fact that actual
A-D conversion falls on a range from “00216” to ”00816” though an output code, “00516”, can be ex-
pected from the theoretical A-D conversion characteristics. Zero error and full-scale error are included
in absolute accuracy.
Also, all the output codes for analog input voltage between VREF and AVcc becomes “3FF16”.
Output code
(result of A-D conversion)
00B16
00A16
00916
00816
00716
+3LSB
Theoretical A-D conversion
characteristic
00616
00516
00416
00316
00216
00116
–3LSB
00016
05
10 15 20 25 30 35
Analog input voltage (mV)
40 45
50 55
Figure 2.7.26. Absolute accuracy (10-bit resolution)
2-137