Maximum current available on the 3.3V pins of the Technic Hub/Boost Hub/City Hub?

[arohrbacher]

As the title says, does anybody know how much current one can draw from the 3.3V supply (pin 3/GND and pin 4/VCC, see The Powered Up connector ) on the PUP sockets of the various LEGO Powered Up hubs? The reason I am asking is that I am working with home-made PUP sensors/displays/etc (see DIY-PU-Sensor ) and want to avoid drawing too much current from the 3.3V line (and possibly destroying something in the hub).
I would imagine that the LEGO 3x3 LED matrix draws quite a bit of current when fully on, but it might be that this item is powered from the "motor PWM" pins 1 and 2 - I can't say for sure as I don't own one of these LEGO matrices...
I tried to find a schematic of the LEGO hubs, but didn't find anything that would tell me more. Even a partial schematic of how the 3.3V are generated from the batteries would help...

Thanks in advance!