Grounding

What is GND?

1.In electronics and electrical engineering, it is by convention we define a point in a circuit as a reference point. This reference point is known as ground (or GND) and carries a voltage of 0V.

2.Typically, this reference point is the base for all other voltage measurements within the circuit. However, not all voltage measurements are taken from this reference point.

3.Earth's ground is exactly as it sounds. It's a ground physically (and electrically) connected to earth via a conductive material such as copper, aluminum, or aluminum alloy. (Earth GND is quite a complex subject).

4.GND has also become the return path for the power supply current in unipolar supply systems.

GND-ing in PCBs

1.In multilayer PCBs GND is majorly offered through a dedicated GND layer plane.

2.A ground plane on a printed circuit board (PCB) is a large area or layer of copper foil connected to the circuit's ground point, usually one terminal of the power supply. It serves as the return path for current from many different components.

3.This serves to make circuit layout easier, allowing the designer to ground any component without having to run additional traces.

4.The large area of copper also conducts the large return currents from many components without significant voltage drops, ensuring that the ground connection of all the components is at the same reference potential.

5.In digital and radio frequency PCBs, the major reason for using large ground planes is to reduce electrical noise and interference through ground loops and to prevent crosstalk between adjacent circuit traces.

6.When a ground plane layer is a present underneath, it forms a transmission line with the trace. The oppositely-directed return currents flow through the ground plane directly beneath the trace. This confines most of the electromagnetic fields to the area near the trace and consequently reduces crosstalk.

Analog and Digital GND

1.Ground planes are sometimes split and then connected by a thin trace. This allows the separation of analog and digital sections of a board or the inputs and outputs of amplifiers.

2.The thin trace has a low enough impedance to keep the two sides very close to the same potential while keeping the ground currents of one side from coupling into the other side.

“A power plane is often used in addition to a ground plane in a multilayer circuit board, to distribute DC power to the active devices. The two facing areas of copper create a large parallel plate decoupling capacitor that prevents noise from being coupled from one circuit to another through the power supply.”

Things to keep in mind while using the GND plane

1.If there’s an open space on your board, fill it with copper and vias to connect with your ground plane.

2.Keep your ground layer whole at all times.

3.Provide a common ground point

4.Be sure to minimize series vias on your ground paths and instead send component grounds directly to your dedicated ground plane.

5.Be sure to properly design your ground first before doing any routing.

6.Know where your currents are going.

7.Always plan for dynamic variance when sending ground connections between boards in a multi-board system

8.The analog parts of your board need to be kept separate. This includes analog-to-digital converters and digital-to-analog converters. When designing the “floor plan” of your PCB, be sure to keep these areas isolated.