I've read a number of posts on this topic, but would like clarification that the following is okay.
I wish to wire a simple switch to an input pin on the ATmega88. The circuit is as simple as the following:
--- Pin -------o o--------- GND
Enabling the internal pull-up on the input pin will ensure it is high when the switch is open, cool. However, when the switch is held closed, the input drops low sourcing current through the pull-up. I'm concerned that an extra resistor should be added somewhere between the pin and ground to limit this current.
The datasheet says that the minimum internal pull-up resistance is 20kOhm, so at 5v this will provide a tiny current, 5/20k = 0.25mA. The power is 1.25mW. This looks to be very small, well below the 40mA DC current limit per pin.
Given I'm not implementing a super-low power device, is my circuit okay, even if the switch is held closed for long periods?