A-D CONVERTER
12.5 Comparison voltage in 8-bit resolution mode
12.5 Comparison voltage in 8-bit resolution mode
In the 8-bit resolution mode, which is selected by the resolution select bit, the high-order 8 bits of the 10-
bit successive approximation register are treated as the A-D conversion result. Accordingly, when compared
with the 8-bit A-D converter, a comparison reference voltage is different by 3VREF/2048. (Refer to the
underlined portions in Table 12.5.1). The difference of the output code change point is generated as shown
in Figure 12.5.1.
Table 12.5.1 Comparison voltage
8-bit A-D converter
M37906’s 8-bit resolution mode
Comparison voltage
Vref
VREF
28
VREF
28
VREF
210
VREF
28
✕✕n –
✕✕0.5
✕✕n –
✕✕0.5
VREF : Reference voltage
n : Contents of successive approximation register
✕8-bit A-D converter’s ideal characteristics (when VREF = 5.12 V)
Output code
(A-D conversion result)
02
01
00
10
30
Analog input voltage (mV)
✕M37906’s A-D converter’s ideal characteristics (when VREF = 5.12 V)
Output code
(A-D conversion result)
10-bit
resolution
resolution
mode
8-bit
10-bit resolution mode
8-bit resolution mode
mode
09
08
07
06
05
04
03
02
01
00
02
(Note)
01
00
(Note)
17.5
37.5
Analog input voltage (mV)
Note: Difference of output code change point
V
REF: Reference voltage
Fig. 12.5.1 Difference of output code change point
7906 Group User’s Manual Rev.2.0
12-17
RENESAS [ RENESAS TECHNOLOGY CORP ]
