Table of Contents
Advertisement
8.5 Comparison voltage in 8-bit mode
In the 8-bit mode, the M37751 treats the high-order 8 bits of the 10-bit successive approximation register
as the conversion result. Accordingly, when compared with the 8-bit A-D converter, the A-D conversion of
the M37751 is performed by using a comparison reference voltage that is different by 3V
the underlined portions in the Table 8.5.1). The difference of the output code change point is generated as
shown in Figure 8.5.1.
Table 8.5.1 Comparison reference voltage of the M37751's 8-bit mode and 8-bit A-D converter
Comparison reference
voltage V
ref
V
: Reference voltage
REF
n : Contents of successive approximation register
8-bit A-D converter with ideal characteristics (In the case of V
(A-D conversion result)
M37751's A-D converter with ideal characteristics (In the case of V
(A-D conversion result)
8-bit mode 10-bit mode
02
01
00
Note
V
REF
Fig. 8.5.1 Difference of output code change point
M37751's 8-bit mode
8
V
/2
n — V
REF
Output code
02
01
00
10
Output code
09
08
07
06
05
04
03
(Note)
02
01
00
Analog input voltage (mV)
: Difference from output code change point
: Reference voltage
7751 Group User's Manual
8.5 Comparison voltage in 8-bit mode
10
/2
0.5
REF
30
(Note)
17.5
37.5
A-D CONVERTER
REF
8-bit A-D converter
8
V
/2
n — V
REF
REF
= 5.12 V)
REF
Analog input voltage (mV)
= 5.12 V)
REF
10-bit mode
8-bit mode
/2048 (refer to
8
/2
0.5
8–15
Advertisement
Table of Contents
