Seamus

I can do that, but your schematic shows the collector of Q3 connected to 3V3

Ah - of course, yes it is. Not quite sure that's a ground, but we can assume that for now. I'll do that later today.

> 3V3 at least has a pulldown (1k8 IIRC) to GND OK - that will be important for the LTSpice model - models actually, as we'll need one model for...

I wanted to throw this into the discussion as a reference schematic for a GPIO pin. Here's [the source](http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/gpio-pin-electrical-specifications), but I think it's been posted by others. The clamp diodes...

> Would be interesting to test what happens, but I highly expect that connecting GPIO3 to GND in LPM will do nothing at all :-) Ach, apologies for that gibberish...

As a variation on your idea for using a transistor, perhaps [an analog switch of this configuration](https://www.vishay.com/doc?70597) would be better suited to this application? I've not been able to find...

> Yes, that would indeed be an option as well. It crossed my mind, but somehow using a switch IC where a transistor is sufficient feels a bit like cheating...

From an earlier post: > > At some point shortly after RPi enters LPM, GLOBAL_EN becomes high once again. GLOBAL_RESET may or may not have anything to do with that...

> For our discussion, I think this is not a really relevant distinction, just using "halt" mode (POWER_OFF_ON_HALT=0) and "LPM" mode (POWER_OFF_ON_HALT=1) is fine. Perhaps *"sleep"* is not relevant, but...

1. RE TS5A3153 & TS5A3154 switches: These have arrived, but I've done nothing with them yet - and I won't be able to make any progress until I return from...