Data Sheet

LABCENTER ELECTRONICS LTD.
28
Managing power nets and power supplies is a very important concept so we’ll experiment a little
to re-enforce the point. Exit the Power Rail Configuration dialogue form, right click on the I2C
memory part and select Edit Properties from the resulting dialogue form. Next, click on the
Hidden Pins button at the right hand side to view the hidden pins and their net assignments.
Hidden Power pins in schematic components.
Let’s change the power pin to be on net VDD, instead of the default of VCC. If we then exit the
dialog and re-invoke the Power Rail Configuration dialogue and switch to the VDD/VCC power
supply we should see that the VCC net is no longer present (this was the only connection on
our schematic so far).
While we are here and for completeness change the Voltage of the power supply to be 3.3V,
which is actually what we will be using. In PCB Design this is useful only as a reference to
ourselves but actually has significance in the software for simulation purposes.
This exercise, while useful in explaining how to view/change the power nets for individual
components, had no effect on design connectivity. The software is clever enough to assign both
the VCC and the VDD nets to the same supply and the Power Rail Configuration dialogue
allows us to configure our power connectivity at design level.
Returning to the schematic now, edit the VDD terminal (right click, edit properties) and change
the terminal label to ‘MY_POWER_NET’. If you go back to the Power Rail Configuration
dialogue you should see that this is now an unconnected power net (a power net which is not
associated with a power supply).