voltage regulator at 4.3V and 0.7V from 5V input that can handle inputs up to +-12V

[davenn]

Try Googling 90004-8076 and see what others have to say about it.....

dozens of property addresses and similar

no IC info .... do you have a couple of specific links please ?

 

[(*steve*)]

When i've tried to put a voltage regulator with a output of 4.3V to replace that line from U10 (or other variants with diodes, or voltage dividers) , the circuit is not able to keep the voltage at that level (4.3V), once i connect the external line to +12V.

I was hoping someone could explain why this IC is able to do it and a simple circuit like those is not ?

That's because it is a current sink, not a current source.

Connecting a 4.3V zener to each supply rail might do the trick, but there won't be any current limit.

 

[mpopeang]

Yes, that will explain this behavior i was seeing.