Ground Questions: Power Supply & PCBs

[Corneo]

I got a question regarding ground in terms of a power supply and another one with regards to PCBs.

Usually you see people put a jumper cable between the negative terminal of a power supply to common ground. Why do people do this? Is it for the user to reference the power supply to actual Earth ground? Isn't the chassis tied to Earth ground using the third prong?

Whats the difference between digital ground and analog ground in terms of a PCB? How are things actually wired in terms of a layout file?

 

[berkeman]

The outputs of many lab power supplies are floating with respect to Earth ground, even if the power supply box uses a 3-prong power cord. This is handy if you want to stack power supplies in series, for example, to make a higher overall voltage.

Separate analog and digital grounds are used generally to keep digital noise out of the analog circuitry. You want to keep the grounds separate, and put the power supply in the middle, to avoid sharing any ground impedance between the distribution of power to the digital and analog sections.

See my discussion of star grounding in this thread, for example, and in the paper that I linked to in my post:

https://www.physicsforums.com/showthread.php?t=213955

 

[oswaler]

I can offer some insight into these questions about ground in relation to power supply and PCBs.

Regarding the first question about jumper cables, this practice is commonly done to ensure a stable and reliable ground connection. By connecting the negative terminal of the power supply to the common ground, any potential differences between the two can be minimized, resulting in a more consistent and accurate power supply output. This is especially important in electronic circuits where even small variations in ground can affect the performance of the circuit.

As for the second question about the difference between digital and analog ground on a PCB, it all comes down to the type of signals being processed. Digital signals operate at high frequencies and have sharp edges, while analog signals are continuous and operate at lower frequencies. Therefore, it is important to have separate ground planes for these signals to avoid interference and maintain signal integrity. In terms of the layout file, these separate ground planes are typically connected at certain points to create a common reference point.

In summary, proper grounding is crucial in electronic circuits to ensure stable and reliable operation. Jumper cables and separate ground planes are common techniques used to achieve this. I would also recommend consulting with an experienced engineer or referencing industry standards for specific guidelines on grounding in your particular application.