Connecting power supply to VCC

[NewSciGuy]

Our design uses the standard global power supplies, VCC, VDD, VEE, and VSS. Our design also has a power supply that generates these voltages. How do I connect the output of the power supply to these global symbols? I get an electrical rules check if I simply connect the output of the regulator to VCC, etc.

[Miguel_V]

Hello,

I'm not sure if I fully understand your question. The components under the Source Group, POWER_SOURCE family (VCC, VDD, etc) are themselves sources. They will supply whatever voltage you set them to so there's no need to connect them to a different power source.

Regards,

[NewSciGuy]

I understand that they act as sources in simulations, but we have a power supply as part of our board design, and we want this to be the source of VCC, etc. We want the circuit board generated from this schematic to have the output of our power supply connected to the same net at the power inputs for the other chips.

Does that make sense? VCC comes from some mystical place otherwise. Is there a better way to design a circuit where the source of VCC is explicit instead of implicit?

I understand that we could simply not use the built in (mystical) power sources and wire up everything explicitly to custom global connectors, but this is a hybrid analog/digital circuit and VCC is implicit on the digital chips making global connectors more error prone.

[Miguel_V]

Hey,

I think I understand. When you export a design to make PCB, you don't use these virtual power supplies (those don't get exported). What you normally do is wire all the power inputs to a connector. These connectors are what connects to whatever it is you are going to use to feed the card. For simulation purposes, use the virtual sources, but for exporting, create connectors. Later on you can make the net that connects all these sources into a ground plane or trace it to whatever you are using as a power source (in real life). You can take a look at the Getting Started sample file in Multisim (the blue folder icon), in there you can see how the nets are all wired to a connector. When this design is exported to Ultiboard All the virtual components will disappear, while the ground, digital ground, power and input nets that are connected to that connector  will be exported (So in this case, It's probably a pin header to connect a function generator, and power supply).

Regards,

[NewSciGuy]

I'm not clear on how this will handle digital IC that don't have an explicit VCC or VSS pin.

[Miguel_V]

Ah,

Sorry, OK I think I actually got it now. My mistake. Yeah Multisim will treat this as a DRC error due to a power pin connecting to a power pin. You have a few options. Use instead of VCC/VDD/etc, On-page labeled connectors. This will be an example of virtual wiring where you simply have the connectors coming off the IC power pins and the power source pins.

Your second option is to simply wire all together before exporting. So wire all the IC power pins to the output of the your onboard power source in one big net.

Your last option is to ignore the DRC error. When the exporting, if you connected the output of your on-board power source to the VCC (per say), it will come out connected to all the thing that share this VCC net. YOu just might not be able to simulate due to the engine finding 2 power sources in parallel.

Regards,