Impressively Low Sleep Currents w/ WDT (90nA) [SOLVED - its really 4.3uA]

[ChemE]

I'm using what Felix sold me a few years ago; I believe that is the 5110.  I have to confess despite reading it here 100 times, I don't know what push pull means in microelectronics.

[perky]

An output from a microprocessor has two MOSFETs inside the chip at the pin, one connects the pin to the power supply (the top FET) and the other connects the pin to GND (the bottom FET). To drive a 1 the processor turns the top FET on and the bottom FET off, the output then gets driven to the power supply voltage. To drive a low the bottom FET is on and the top FET off, the output then gets driven to GND. This is a push-pull circuit, also know as totem pole, as it 'pushes' current out in the 1 state and 'pulls' current in in the low state. An open drain (also sometime called open collector) only ever turns the bottom FET on while the top FET is always off, it relies on a pull-up to pull the pin to a 1 when the bottom FET is off.

Mark.

[ChemE]

Thanks for the explanation Mark, that makes perfect sense to me now.  Much obliged!