[SOLVED] what shoud I do with AREF & RESET pins in AVR?

[Cyrus the Great]

what shoud I do with AVCC & RESET pins in AVR?

hi.I want design PCB for my circuit which its has a ATmega 16.I heard that I should pull-up the AVCC pin to protect it from noise.is it true what I heard or no.and my another question is that when I want update my schematic to pcb in altium designer there is a warning which said that the reset pin is float. should I connected to the ground or no?

 

[alexan_e]

I heard that I should pull-up the AVCC pin to protect it from noise.is it true

I'm not sure what you mean by pull-up, you mean with a resistor?
Here is what the datasheet says in the pin description

AVCC is the supply voltage pin for Port A and the A/D Converter. It should be externally con-
nected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC
through a low-pass filter.

You should definetelly connect it to Vcc

there is a warning which said that the reset pin is float

The reset pin is pulled up internally but there can be cases with noisy enviromnet that can pull the pin down so it would be probably beneficial to add an external resistor.
Refer to http://www.atmel.com/images/atmel-2...gn-considerations_application-note_avr042.pdf

 

[Cyrus the Great]

thank you.the pdf is what I need.so its better to connect the Reset pin with a 330 ohm resistor to the ground even I don't need the external reset in my circuit ?

 

[alexan_e]

The internal pullup is about 30K-60K , for an external one you wouldn't need to go below 4k7 - 10K

I personally don't use the reset resistor for my hobby projects but for production PCB I would suggest you use it.

Also note the following in the PDF I linked

The recommended pull-up resistor is 4.7kΩ or larger when using STK500 for programming.
For DebugWIRE to function properly, the pull-up must not be smaller than 10kΩ.

 

[Cyrus the Great]

thank you so much.
with the best regard.