M37281EKSP Datasheet, PDF (53/172 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER

M37281MAH–XXXSP,M37281MFH–XXXSP,M37281MKH–XXXSP, M37281EKSP
8.8.8 Definition of A-D Conversion Accuracy
The definition of A-D conversion accuracy is described below (refer
to Figure 8.8.4).
Accuracy is shown the difference between measurement result out-
put code and output code which is expected for A-D conversion whose
specification is ideal by using LSB.
The analog input voltage in accuracy measurement is made to be a
middle point of input voltage width (=1 LSB) which outputs the code
in which the A-D converter with the ideal characteristics is identical.
For example, 1 LSB’s width is 20 mV at VREF = 5.12V.
0 mV, 20 mV, 40 mV and 60 mV are selected for analog input voltage.
A-D conversion accuracy is shown in Fig 8.8.4.
That the output code expected in the ideal A-D converter is “0516”
shows that there is actual A-D conversion result with in “0316” to “0716”
on the = ±2LSB absolute accuracy, when the analog input voltage is
100 mV.
And, zero error and scale error are contained for the absolute accu-
racy, and the quantization error is not contained.
Output code
0916
0816
0716
0616
0516
0416
Absolute accuracy
+ 2LSB
Ideal A-D conversion
characteristics
Limitless resolution A-D
conversion characteristics
0316
0216
– 2LSB
0116
0016
0
20 40
60 80 100 120 140 160 180 200 220
Analog input voltage (mV)
Fig. 8.8.4 Definition of A-D Conversion Accuracy
Rev.1.01 2003.07.16 page 53 of 170