F²MC-16FX Family, Hardware Set Up
Document No. 002-04772 Rev. *B
13
The frequency of the oscillation can be calculated by
DB
X
OSC
C
L
f
2
1
.
The inductivity L
X
is the unknown value and depends on the PCB, its routing, and the wire lengths.
There are two counter measurements to prevent from latch-up.
One solution is to decrease the capacity of the debouncing capacitor. This increases the oscillation frequency, and
the over-all energy of the overshoots is smaller.
“big” capacity “small” capacity
This solution has two disadvantages: First the debouncing effect decreases and second, there is no guarantee, that
the latch-up condition is eliminated.
A better solution is to use a series resistor at the port pin like in the following schematic:
