Electronic – Does ATtiny RESET pin need a resistor


I need to make sure that my ATtiny does not reset unexpectedly. To do that, I am planning on connecting the RESET pin directly to VCC.

However, I have heard some places that you need a 10k resistor between VCC and the RESET pin, to prevent too much current from flowing into the RESET pin and burning the IC. I have also seen some places that you do not need a resistor between VCC and RESET, and I have also read a few places that you do not even need to connect RESET to anything, because it is pulled high internally.

I could not find any definitive answer on this, and I would like to know what the case would be for each of these condidions (directly to VCC, VCC through resistor, don't connect RESET pin at all) is.

Best Answer

I don't think theres a technical reason why you couldn't connect your reset pin directly to +V, as long as it was already programmed and you never wanted to modify that program. As far as I'm aware, there is no function of the attiny that requires the reset pin to be pulled low (for example, the watchdog timer doesn't try to pull the reset line low).

Having said that, there isn't really a good reason why you would want to have the line directly connected, and there are quite a few where you wouldn't want it to be directly connected (like programming, and manual reset etc).

The attiny does have an internal pull-up to VCC, but its quite weak (~100k iirc), so environmental conditions could cause a spontaneous reset. If you're worried about this, you should use an external pull-up resistor. It means using an extra component, but it's safer, especially if your reset pin is routed to a programming connector.