AVR-Chat

One way is to add a series resistor to each input (say 4.7K to 10K),  
then add a diode (preferably Schottkey,j but silicon junction will  
work) from each input to the processor Vcc, cathode to Vcc. That will  
limit each input at the micro to the current Vcc )(plus one diode drop).

Jim Wagner
Oregon Research Electronics
On Jul 28, 2009, at 7:40 PM, Brian wrote:

> I made a module for a car to monitor inputs. Since inputs can only  
> be VCC +/-0.5V for a high signal, how do you keep the inputs from  
> getting to the micro before VCC is applied? It keeps blowing my  
> inputs so they dont work.
>
> One thing I thought about is using a mosfet switch controlled by an  
> output of the micro to allow the signal only once it is started up.
>
> Brian
>
>
> 



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