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STAR Ground - Joining nets at one point

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Сообщение 1 из 4
mark.richardsFWCEV
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STAR Ground - Joining nets at one point

As a very long time DipTrace user, the transition to Eagle has been horrific.  However, I am now able to create new components, manage libraries, and perform schematic capture.  (PC Board layout is the next learning curve).  Going from a simple and logical GUI to Eagle's more restrictive and somewhat non-intuitive interfaces emptied a few aspirin bottles.  With the issue below, I may have to lean upon a strong drink.

 

My designs often mix analog and digital and demand separate grounds/planes that meet at a single point (called a STAR ground).  This is managed in DipTrace using a zero-ohm jumper at the desired STAR point.  I'd like to evolve beyond this to a better way.

 

How have others provided for this in Eagle?  How?

 

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Сообщение 2 из 4
C.Nicks
в ответ: mark.richardsFWCEV

Hi Mark,

What I tend to do to isolate ground sections is use the Restrict layers (41 & 42) to keep grounds from pouring into areas. Any shape you draw in the Restrict layer will create a cutout in polygons. Alternatively you can use a resistor or inductor at the star point as you've mentioned. When I do this I use a different gnd supply symbol and net for digital and analog grounds. If you do this make sure you have different polygon ranks so that the polygons don't pour together.

The Restrict layer is very handy when designing pours. When I temporarily switched to Altium, I really missed the simplicity of Eagle's polygon handling and restrict layer. You can place text, wires, rectangles, and polygons on the restrict layer.

 

- Cameron

Best Regards,
Cameron


Eagle Library Resources


Kudos are much appreciated if the information I have shared is helpful to you and/or others.
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Сообщение 3 из 4

Hi mark.richardsFWCEV,

 

Thank you for participating. Cameron's suggestion is a very good option and one I would encourage you to consider. Here are couple of others:

 

1. Use a 0 ohm jumper part, which you can easily make by making a component with 2 surface mount pads and shorting them together in the package.

 

2. Polygons with different signals will short if they overlap, so you can keep your digital and analog grounds separate and just have the polygons overlap at one point(preferably near the power supply), if they have the same rank(by default they do) then they will short together. When you run the DRC you'll get a couple of errors but you can approve them.

 

I personally tend to favor option 2, but as you can see there are a few ways to skin this cat.

 

Please accept as solution if my post fully resolves or you issue, or reply with additional details if the problem persists.

 

Let me know if there's anything I can do for you.

 

Best Regards,



Jorge Garcia
​Product Support Specialist for Fusion 360 and EAGLE

Kudos are much appreciated if the information I have shared is helpful to you and/or others.

Did this resolve your issue? Please accept it "As a Solution" so others may benefit from it.
Сообщение 4 из 4

Thanks to both for responding.

 

I think the technique that will work best for me is a device with two nodes which have distinct pins but which is also connected physically.  The same as a cut-jumper.  So I created an 0805 surface mount pad and bridged these internally with a rectangle on the TOP layer.  I haven't brought this up to a pc board yet, so not certain the rectangle will be treated as copper.  By using a rectangle, I am trying to avoid 3 pads and also hoping I will not be hit with a DRC error.

 

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