Go Down

Topic: protection for digital input pin (Read 1 time) previous topic - next topic

fungus


Quote
So you don't need any more.

Yes you do. 1mA is the maximum current that should flow through the internal protection diodes.


I actually said:

So you don't need any more.

(Assuming you've limited the number of amps that can reach the pin, eg. though a 10k resistor)

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Grumpy_Mike

Quote
(Assuming you've limited the number of amps that can reach the pin, eg. though a 10k resistor)

The thing is that once you start putting 10K series resistors on inputs your noise immunity is shot and it limits the rise time of the signals. That is why I have a 22R series resistor so the protection circuit does not end up crippling the signal.

tvcsantos


It's my page so yes I think it is good especially if you are only protecting against transients. If the voltage is going to be constantly over 5V then make that resistor something like 100R.


Got it :)

I don't have a 100pF can I use other values?

What impact the capacitor values have?

Grumpy_Mike

Quote
I don't have a 100pF can I use other values?

Yes, using other values will control the balance between protection against spikes and disrupting the input signal.
The capacitor absorbs voltage spikes ( good ) and also slows down the input rise time ( bad ) .

Go Up