Fujitsu ALL FR 460 Series Application Note page 17

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FR460 Hardware Set Up

Chapter 3 Port Input / Unused Pins / Latch-up

But at the port pin Pxy on point (B) the following voltage can be measured:

By closing the switch SW the circuit becomes a parallel oscillator with the wire-inductivity L

the debouncing capacity C

and the damping R

of the pull-down resistor (Assume the power

supply to be ideal, i. e. it has no internal resistance):

Because R

is often chosen high (> 50 K Ohms), its damping effect is weak.

This (weakly) attenuated oscillator causes voltage overshoots on the port pin, drawn in red in

the illustration below:

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MCU-AN-300033-E-V13

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