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About sampling time of A/D converter

Last Updated:01/16/2018

Question:

Normal 1 mode or Normal 2 mode can be selected by the LV0 bit in the A/D converter mode register 0 (ADM0). However, the number of sampling clocks varies depending on the mode. How should I select a mode?

Answer:

Please select an appropriate mode according to the output impedance of the analog input source of your system.
When the output impedance is high;
if the sampling time is short, the internal sample & hold circuit may not get charged completely, which may cause a failure in obtaining an expected conversion accuracy.
Meanwhile, if the sampling time is long, the internal sample & hold circuit may not get charged sufficiently due to dynamic changes in the input voltage.
Please be sure to sufficiently check the sampling clocks with your system.

Remarks:
Number of sampling clocks in Normal 1 mode: 7 clocks (fAD)
Number of sampling clocks in Normal 2 mode: 5 clocks (fAD)

Suitable Products
RL78/F12
RL78/F13
RL78/F14
RL78/F15
RL78/D1A
RL78/G13
RL78/G14