32185 Datasheet, PDF (547/1032 Pages) Renesas Technology Corp – MCU

11
A/D CONVERTER
11.5 Notes on Using A/D Converter
Table 11.5.1 Sampling Time (in Which C2 Needs to Be Charged)
Conversion start method Conversion speed
2BCLK mode Single mode
(when sample-and-hold
disabled or normal
sample-and-hod enabled
Single mode
(when fast sample-
and-hold enabled)
Slow mode
Fast mode
Slow mode
Fast mode
Comparator mode
Slow mode
Fast mode
Simultaneous
sampling
Slow mode
Fast mode
BCLK mode
Single mode
(when sample-and-hold
disabled or normal
sample-and-hod enabled
Single mode
(when fast sample-
and-hold enabled)
Slow mode
Fast mode
Slow mode
Fast mode
Comparator mode
Slow mode
Fast mode
Simultaneous
sampling
Slow mode
Fast mode
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Normal speed
Double speed
Sampling time
for the first bit
55BCLK
31BCLK
23BCLK
15BCLK
55BCLK
31BCLK
23BCLK
15BCLK
55BCLK
31BCLK
23BCLK
15BCLK
55BCLK
31BCLK
23BCLK
15BCLK
27.5BCLK
15.5BCLK
11.5BCLK
7.5BCLK
27.5BCLK
15.5BCLK
11.5BCLK
7.5BCLK
27.5BCLK
15.5BCLK
11.5BCLK
7.5BCLK
27.5BCLK
15.5BCLK
11.5BCLK
7.5BCLK
Sampling time for the
2nd and subsequent bits
27BCLK
15BCLK
11BCLK
7BCLK
–
–
–
–
–
–
–
–
–
–
–
–
13.5BCLK
7.5BCLK
5.5BCLK
3.5BCLK
–
–
–
–
–
–
–
–
–
–
–
–
Therefore, the time in which C2 needs to be charged is found from Eq. B-1, as follows:
Sampling time (in which C2 needs to be charged) > Cin × R1 + C2(R1 + R2)Eq. B-2
Thus, the maximum value of R1 can be obtained as a criterion from the equation below. Note, how-
ever, that for single mode (when sample-and-hold is disabled), the sampling time for the second and
subsequent bits (C2 charging time) must be applied.
R1 ^{< C2 charging time - C2 × R2}
Cin + C2
32185/32186 Group Hardware Manual
Rev.1.10 REJ09B0235-0110 May 15, 07
11-49