
CHAPTER 9 A/D CONVERTER (
μPD78F921x ONLY)
User’s Manual U16994EJ6V0UD
158
Table 9-1. Sampling Time and A/D Conversion Time
fXP = 8 MHz
fXP = 10 MHz
Reference
Voltage
Range
Note 1
Sampling
Time
Note 2
Conversion
Time
Note 3
Sampling
Time
Note 2
Conversion
Time
Note 3
Sampling
Time
Note 2
Conversion
Time
Note 3
FR2
FR1
FR0
VDD
≥ 4.5 V
12/fXP
36/fXP
1.5
μs
4.5
μs
1.2
μs
3.6
μs
0
VDD
≥ 4.0 V
24/fXP
72/fXP
3.0
μs
9.0
μs
2.4
μs
7.2
μs
1
0
96/fXP
144/fXP
12.0
μs
18.0
μs
9.6
μs
14.4
μs
1
0
48/fXP
96/fXP
6.0
μs
12.0
μs
4.8
μs
9.6
μs
1
0
1
48/fXP
72/fXP
6.0
μs
9.0
μs
4.8
μs
7.2
μs
0
1
0
VDD
≥ 2.85 V
24/fXP
48/fXP
3.0
μs
6.0
μs
Setting
prohibited
Note 4
(2.4
μs)
Setting
prohibited
Note 4
(4.8
μs)
0
1
176/fXP
224/fXP
22.0
μs
28.0
μs
17.6
μs
22.4
μs
1
VDD
≥ 2.7 V
88/fXP
112/fXP
11.0
μs
14.0
μs
Setting
prohibited
Note 4
(8.8
μs)
Setting
prohibited
Note 4
(11.2
μs)
0
1
Notes 1.
Be sure to set the FR2, FR1, and FR0, in accordance with the reference voltage so that Notes 2 and 3
below are satisfied.
Example When VDD
≥ 2.7 V, fXP = 8 MHz
The sampling time is 11.0
μs or more and the A/D conversion time is 14.0 μs or more and 100 μs or
less.
Set FR2, FR1, and FR0 = 0, 1, 1 or 1, 1, 1.
2.
Set the sampling time as follows.
VDD ≥ 4.5 V:
1.0
μs or more
VDD ≥ 4.0 V:
2.4
μs or more
VDD ≥ 2.85 V:
3.0
μs or more
VDD ≥ 2.7 V:
11.0
μs or more
3.
Set the A/D conversion time as follows.
VDD ≥ 4.5 V:
3.0
μs or more and less than 100 μs
VDD ≥ 4.0 V:
4.8
μs or more and less than 100 μs
VDD ≥ 2.85 V:
6.0
μs or more and less than 100 μs
VDD ≥ 2.7 V:
14.0
μs or more and less than 100 μs
4.
Setting is prohibited because the values do not satisfy the condition of Notes 2 or 3.
Caution
The above sampling time and conversion time do not include the clock frequency error. Select
the sampling time and conversion time such that Notes 2 and 3 above are satisfied, while taking
the clock frequency error into consideration (an error margin maximum of
±5% when using the
high-speed internal oscillator).
Remarks 1.
fXP: Oscillation frequency of clock to peripheral hardware
2.
The conversion time refers to the total of the sampling time and the time from successively
comparing with the sampling value until the conversion result is output.