I be damned
found another option...
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The BJT is lacking the intrinsic diode thus blocking current both ways, and those most modern late PNP BJT are quite on par with those recent MOSFET switches!
enter:
2SAR552PIt can be driven off 30mA pins, can drive up to 3A pulses (way over USB supply) all in all a simpler switch, and if anything odd where to happen i have the fly back diode in place on the base (brought to bear should reverse current ever flow over the device)
Why this exotic PNP/PMOS layout you may wonder?
Earlier I have decided to have all the backlit LEDs connected to common ground to make the PCB layout simpler, this mandates so called high side switching, and as far as i am aware this is most reliably achieved with BJT.
This is so due to BJT being current controlled devices that only slightly depend to discrete voltage levels - which are a moving target in said high side switching.
Further a note on the dreaded BJT thermal runaway (losing resistance under load and when heating up):
If a single device is used this is totally no issue - it loses resistance as it heats up - thus heating up less - that's about all
It remains only to find out the proper amount of
milimaps required per LED to achieve the needed level for a backlit key effect.
This is the more difficult as we actually try make a board for more than just one color of LEDs (white, blue, amber, maybe more)
Am i overthinking this?