Seperate 0v trace from Ground plane

[Lucither]

Hi,

Is there a way of having a ground plane (net 0) as well as a seperate trace that is also on net 0, the idea being that the seperate trace is carrying high current and i dont want it being drawn on the ground plane. When i draw the trace and then add a ground plane it all joins together, ideally i only want the 2 to meet at the input connector. I have worked around this in the past by placing a dummy ferite on the board and assigning the other side of it to DGND but was hoping for an inbuilt way of handling this.

Thanks for any advice.

Rgs,

Lucither.

[_user32 · Accepted solution]

Rgs,

You have a few methods of doing this...

A. Separate grounds tied with net bridge.

You can implement the design like you've already done - create ground 'net 0' and create a separate ground net 'cgnd' or 'dgnd', etc...  For these nets, rather than create a powerplane (Place -> Powerplane...) create a separate copper area (Place -> Copper area) for each individual net.   Rather than tie them together with a 'fake' component, you can tie them together with a net bridge (Place -> Net Bridge) to create a star ground connection at a single point.   The one drawback to a net bridge is that it is only managed in Ultiboard - there is no reference back to it in Multisim.   You could create a simulation only resistor part (black in color) in Multisim with a very low value and label this R_netbridge to account for this and tie it between 'net 0' and your alternate ground.   I have also previously posted about alternate grounds and symbols that you can use.   I've also requested this for a future Multisim version.

http://forums.ni.com/t5/Circuit-Design-Suite-Multisim/Isolated-Ground-and-Analog-Ground-in-Multisim/...

B. Single ground net split with polygon splitter.

You can create a single ground plane (Place -> Powerplane...) and then use the polygon splitter to divide up the plane such that the high current will only flow back to the star ground point.   The tool is located in the menu (Design -> Polygon Spllitter) - Note - I believe its available only on UB PowerPro as well.   At this point the user needs to define how the plane is carved out.  Be sure that you are not carving out islands that do not connect back to a common point.    One tip is to start from an edge of the board or polygon and work towards the star ground point.   Also note that some of the polygon / plane settings can reverse the polygon splitter settings so you may need to adjust the settings if you are not getting good results.   If you activate the plane and go to properties - the 'Copper Area' tab has the void/island settings that I am giving a caution about.

C. Create single net, use Copper Area to separate

You can create a single net, but then use the Place->Copper Area to manually separate the plane as needed.   The polygon tool allows you to create individual islands - and you'll need to manually tie them together at a single point.

Regards,

Pat

[Lucither]

_User32 many thanks. I am just on my way out but after a quick glance i beleive that you have given me what i need. Looks like i have a bit of playing around to do testing all the ideas you have posted. Will do this shortly.

Thanks again,

Lucither.

[Lucither]

User32,

Just for your interest i used the suggestion of a net-bridge, works perfectly for my current situation, many thanks. Will also give your other option a looking over as this is a situation i find myself in nearly every design and want to get the process as slick as possible.

Many thanks,

Lucither.