CHAPTER 13 A/D CONVERTER
Preliminary User’s Manual U17260EJ3V1UD
309
Table 13-2. A/D Conversion Time Selection
(1) 2.7 V
≤
AV
REF
≤
5.5 V
A/D Converter Mode Register (ADM)
Conversion Time Selection
Conversion Time Configuration
FR2 FR1 FR0 LV1 LV0
f
PRS
=
2 MHz
f
PRS
=
10 MHz
f
PRS
=
20 MHz
Note
Conversion
Clock
(f
AD
)
SAR
Clear
Sampling Successive
Conversion
Time
ADCR
Transfer,
INTAD
Generation
0 0 0 0 0
264/f
PRS
26.4
µ
s 13.2
µ
s
Note
f
PRS
/12
0 0 1 0 0
176/f
PRS
17.6
µ
s 8.8
µ
s
Note
f
PRS
/8
0 1 0 0 0
132/f
PRS
13.2
µ
s 6.6
µ
s
Note
f
PRS
/6
0 1 1 0 0
88/f
PRS
Setting
prohibited
8.8
µ
s
Note
f
PRS
/4
1 0 0 0 0
66/f
PRS
33.0
µ
s 6.6
µ
s
Note
f
PRS
/3
1 0 1 0 0
44/f
PRS
22.0
µ
s
Setting
prohibited
Setting
prohibited
f
PRS
/2
2/f
AD
6/f
AD
12/f
AD
2/f
AD
Other than above
Setting prohibited
Note
This can be set only when 4.0 V
≤
AV
REF
≤
5.5 V.
(2) 2.3 V
≤
AV
REF
< 2.7 V
A/D Converter Mode Register (ADM)
Conversion Time Selection
Conversion Time Configuration
FR2 FR1 FR0 LV1 LV0
f
PRS
=
2 MHz
f
PRS
=
5 MHz
Conversion
Clock
(f
AD
)
SAR
Clear
Sampling Successive
Conversion
Time
ADCR
Transfer,
INTAD
Generation
0 0 0 0 1
480/f
PRS
Setting
prohibited
f
PRS
/12
0 0 1 0 1
320/f
PRS
64.0
µ
s f
PRS
/8
0 1 0 0 1
240/f
PRS
48.0
µ
s f
PRS
/6
0 1 1 0 1
160/f
PRS
Setting
prohibited
32.0
µ
s f
PRS
/4
1 0 0 0 1
120/f
PRS
60.0
µ
s Setting
prohibited
f
PRS
/3
1 0 1 0 1
80/f
PRS
40.0
µ
s Setting
prohibited
f
PRS
/2
2/f
AD
24/f
AD
12/f
AD
2/f
AD
Other than above
Setting prohibited
Cautions 1. Set the conversion times with the following conditions.
•
4.0 V
≤
AV
REF
≤
5.5 V: Sa successive conversion time = 5 to 30
µ
s
(f
AD
= 0.6 to 3.6 MHz)
•
2.7 V
≤
AV
REF
< 4.0 V: Sa successive conversion time = 10 to 30
µ
s
(f
AD
= 0.6 to 1.8 MHz)
•
2.3 V
≤
AV
REF
< 2.7 V: Sa successive conversion time = 25 to 62
µ
s
(f
AD
= 0.6 to 1.48 MHz)
2. When rewriting FR2 to FR0, LV1, and LV0 to other than the same data, stop A/D conversion
once (ADCS = 0) beforehand.
3. Change LV1 and LV0 from the default value, when 2.3 V
≤
AV
REF
< 2.7 V.
4. The above conversion time does not include clock frequency errors. Select conversion time,
taking clock frequency errors into consideration.
Remark
f
PRS
: Peripheral hardware clock frequency