I'm going to use an ATtiny85 for a project running from a lithium battery. It's a relatively high-power project (up to 4A at times) so I was going to use a MOSFET as a switch, and have the ATtiny control the MOSFET. I want it to shut off at a certain voltage for low-voltage protection on the battery. I've seen on the 85's spec sheet is has Vcc, or internal reference voltages of 2.56 (needs 3V minimum for this), or 1.1V. I want it to turn off at 2.5V~2.6V for the batteries I have (they say they're safe to 2.4V, but just want to be a little safer). Would the best way be to accomplish this be to use a voltage divider of appx 40% against the internal 1.1V, and then when it drops below saturation it would know the voltage must be low? Or is there a better way to accomplish this task?