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Electronics => Electronics => Topic started by: airman00 on September 13, 2009, 09:32:40 AM

Title: Pullup Resistor on Reset Pin
Post by: airman00 on September 13, 2009, 09:32:40 AM

I've always used either 4.7k or 10k on my RESET pins on AVRs, but glancing at the datasheet of the ATmega325P ( the AVR i'm using) , I see that the pullup should be between 20K ohm and 100 K ohm.
So what's happening there? I'm using a 10K resistor and everything seems fine, but I wonder why the datasheet writes that the minimum is 20k.

Title: Re: Pullup Resistor on Reset Pin
Post by: Soeren on September 13, 2009, 01:18:30 PM

Hi,

That shouldn't be an issue.
The upper limit is defined only by the input current and how much noise you expect in the are they're placed. The lower limit is only defined by the output impedance of what you use to drive it with.

To save current go high impedance, but beware of getting too high, or noise will be a problem.