[sdiy] Gate input protection

Seb Francis seb at burnit.co.uk
Sat Nov 15 02:05:40 CET 2008


Samppa Tolvanen wrote:
> On Sat, Nov 15, 2008 at 1:56 AM, Seb Francis <seb at burnit.co.uk> wrote:
>
>   
>> The first option looks an elegant solution, but I'm not sure it's safe if a
>> negative gate signal would be present.  Then the forward voltage across the
>> zener (~1V) would allow -1V at the dsPIC input.  Or is the 100K resistor
>> enough to make this ok?  Is there a simple way to add protection for -ve
>> gate voltages?
>>
>>     
>
> mmm - maybe just throwing in a forward biased diode after the resistor?
>   

Duh, kind of obvious now you mention it!

And Eric's solution of using a resistor + schottky array looks ideal, 1 
part less to solder.

Thank you :)
Seb







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