For powering a RS485 circuit, I am requiring a Negative Power Source.

I was thinking to split a standard power source with 0V, +6V and +12V, using the +6V as ground with LM7805, and using some LM7805|LM7905 (or similar) devices for regulate into +5V|-5V.

In this case, the +6V could become a sinking terminal if the negative voltage circuit is unloaded, which I think should not be correct and could break the source(?).

The arbitrary change of GNDs confuse me, because the GND should always be a sinking terminal, not a sourcing.

So, how should I generate +5V -5V sources in a proper way?

Also, it is a choice to generate a low power -5V from a +5V source?

[![enter image description here](https://i.stack.imgur.com/6Ihhr.png)](https://i.stack.imgur.com/6Ihhr.png)

Edit.

* Agreed regarding RS485 not actually requiring -5V source. Please keep the example valid for other application.
* Consider 0V, +7.5V and +15V for the voltage dropout.
* Consider only resistive loads, DC output signals.

In the best case, I am afraid this question depends on the nature of the power source (?). For example, 

* Case 1: if we have two sources, one from GND to +7.5V and other from GND to +15V, then loading only the 7805 will negatively polarize (charge) the 0 +7.5V source (?), hence this design is wrong in this case?
* Case 2: The proper design should have two sources from GND to +7.5V, and putting them in series (?).

[![enter image description here](https://i.stack.imgur.com/o6dr9.png)](https://i.stack.imgur.com/o6dr9.png)