IEEE circuit schematic standards
You should consider the circuit schematic a "Figure" and follow the guidelines for figures (with respects to labeling, referencing and spacing). If you are using LaTeX, I'd recommend taking a look at the circuitikz package.


  Can i for example show a simplified version of my schematic? or do I need to put the whole schematic in the paper?


Figures, as in any paper, should have clear readibility. It probably isn't worth showing things such as power supply input circuitry, they would just clutter the figure. Yet one must remember that a good paper is also a reproducible one. Keep the schematic clean, stick to the important bits, and keep it reproducible by any half-decent engineer. If you wish the readers to have access to the full schematic, I'd recommend doing so through a weblink.