Hardware manual

Microcomputer Technical Q&A
132
Q&A No.: QAH8S-245
Category: A/D Converter
Subject: A/D Conversion Time in Simultaneous Sampling Operation
Question
What is the A/D conversion time in simultaneous sampling operation?
Answer
The conversion time is normally 1 µs, but with simultaneous sampling, as shown in the figure
below, the conversion time for even-numbered conversions (B and D) is twice that for odd-
numbered conversions (A and C). The conversion time is thus 1 µs for even-numbered
conversions and 2 µs for odd-numbered conversions.
Sample A
Sample B
Sample C
Sample D
t
D
0.15 µs
(3 cycles)
t
SPL
1 µs
(20 cycles)
t
CP
1 µs
(20 cycles)
t
CP
2 µs
(40 cycles)
t
SPL
1 µs
(20 cycles)
t
CP
1 µs
(20 cycles)
t
CP
2 µs
(40 cycles)
t
F
0.05 µs
(1 cycle)
φ
Address
Write signal
ADST
Sampling
timing
A/D conversion
operation
timing
ADF
Conversion
A
Conversion
B
Conversion
C
Conversion
D
(20 MHz)
A/D Conversion Times in Simultaneous Sampling Operation