Ground properties viz power and digital

Question

What is the difference between power ground and digital ground ? What I understand is that the pgnd is the path through which the supply current discharges. Now the DGND, is the ground reference to the digital signals. How are they eventually connected ? Via a star connection ?

Another thing. If INA MCU we have 4 gnd pins which or rather how many will act as a pgnd and how many is dgnd ? Is there some logic in this ?

For eg - a signal from a gpio in an MCU will have a small current. This will travel via the gpio track into the other end and then go into the ground via ,say a and pin of that chip. So, which gnd pin will it take to discharge into the gnd plane ? If ,say that other ic is an ic with just 1 gnd pin, how can it be classed ? So, pgnd and dgnd are quite loosely used and can be interchanged. In fact many chips have just 1 ground pin. So that pin is a power ground or a digital ground ? The way I see it, it serves as both. So this is a disadvantage as well. Because any noise on the supply rail can cause a ground imbalance. Likewise with digital part can dump a lot of noise on ground.

Answer 1

Different grounds are a design choice. Depending on the expected currents and expected interference grounds are separated on chip and / or on PCB or even in a complete system (finished product). There are no rules to do it like this or like that to guarantee succes. A strategy is chosen at the design phase and that is implemented. Sometimes certain ground connections are prepared on a PCB and conmnected or left open in the final design depending on tests. Experienced engineers usually know which strategy to choose in a certain situation.

You worry too much about these things but have too little knowledge to understand why to choose which strategy. Why is this so important to you to understand this all now ? Some things require experience, this is one of them. Join a team with experienced engineers and learn from them.