So, I am building the soft-on/off circuit shown below and described here on a breadboard to test it out before I actually put it into a design.
However, to better fit the parts on hand, I decided to alter a couple of the R and C values slightly, and use a pair of TO-220 FETs instead of the SO-8 dual FET, resulting in this:
simulate this circuit – Schematic created using CircuitLab
which yields the simulation results below when turned on without RL connected (NFG tracks Vout in both plots, so it's not shown):
and with RL connected for a 10mA load at full Vout (PFG, Vin, and PB track each other here):
However, when I prototype the same circuit that's in the simulation, without a load, I get this gem of a result on power-on:
Along with that, Vout comes up to a steady 12V, tracking Vin. What in the world could I have done wrong here? Is the circuit given really that sensitive to part selection? Or how could I have miswired it to produce the results I'm receiving? And where on Earth is that 370us pulse on PFG at startup coming from?
Best Answer
Summary from comments: I think you need a load for this circuit to work.
Shamelessly taking credit for this, here is an answer for you to mark :)
You should also take a look at Linear Technology's line of push button controllers. They are very low power and have worked well for me in the past.