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Cable capacitance issues?

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conmanxx

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Hello,

Currently I'm working on a project, we are seeing some strange behaviour.

We are reading inputs through back panel of an instrument. all input lines are pulled high to 5V through 10K resistor.
A simple external contact closure will then pull the input lines low

These inputs are connected to a TXS0108E voltage level translator which converts inputs down to 3.3V,

We observe when we plug cable onto these input lines the outputs of the TXS0108E start flicking high/low intermittently.
We believe the cable capacitance is causing the issue.

Has any one seen similar problems?
Any advice on how to solve the issue?
A buffer maybe is the way to go between the cable and the TXS0108E?
 

FvM said:
How about debouncing the inputs in software?
Click to expand...

Adding hysteresis is it? I.e Input must be constantly low for a period of miilseconds before it is accepted?

Hmm worth considering

Would prefer a hardware solutution!
 

How about a .1uf capacitor between the input(s) and ground?
 

As we have no idea what the expected switching rate/frequency is in your application, it is kind of hard to suggest a value, but a simple low pass RC filter on the input should do it - if the wiring is going out to mechanical switches/relays, you should probably have some filtering and/or transorbs or clamping diodes on the inputs anyway to protect from switching transient voltage spikes.
 

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