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I'm making a PCB with two ground signals, power ground and signal ground. These two shall be connected together at one spot on the PCB, after recommendations from the datasheet. But how is this done in the schematic? I can't simply connect these two together, since it will then be interpreted as one net and give a DRC error. Any help is appreciated. The schematic is done in Altium Designer.

Here is the schematic of the demo board which I have based my design on, a connection between SGND and GND is done on the bottom if the schematic.

http://cds.linear.com/docs/en/demo-board-schematic/DC2044A-2-SCH.PDF

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You can create something called a net tie. Net Ties and how to use them

Alternatively, you can place a zero ohm resistor, or a ferrite bead between the two grounds.

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Treat them as too separate nets and then join them at one point with a zero ohm link/resistor.

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Also, be aware of capacitive coupling between the layers. If the PCB tool uses one layer of copper for one ground, and another layer for the other ground, you get two large copper planes separated by a very small distance, with a dielectric layer in between. If this sounds familiar, it's because it describes a capacitor. There are two basic approaches to solve this. First, put both grounds on one layer. Then all coupling is "sideways" and is very small. The second is to put a third layer in between the two layers, connected to ground at one point. It shields the two layers from each other, and is often called a Faraday layer. (See "Faraday box" for explanation.)

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