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I learnt that the digital (microcontroller), analog (ADC reference) and power lines (For motors) have to have their own seperate areas when it comes to partitioned ground schemes. In an application, A hot-swap eFuse chip along with an LDO are used and I have connected the grounds as seen in the below figure. Gnd for digital return lines, AGnd for analog and PGnd for power return lines. And these return paths connected to a common ground using the ferrite beads. Is this a legit way to connect grounds together? please let me know the points to consider if not. Thanks.

Grounding

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    \$\begingroup\$ Putting what is basically a resistor between grounds is a bad idea. It means your ground voltages will vary with respect to each other. Instead of trying to resistively isolate the grounds, route your ground currents so that they don't interfere with your ADC. \$\endgroup\$ Commented Oct 7, 2022 at 12:51
  • \$\begingroup\$ @user1850479 Thanks for the response. But those are ferrite beads: a high current ferrite bead for power ground and a wideband ferrite bead for the analog ground. As far as I know they are only resistive to a certain noise frequency which is its intended purpose. Please correct me if I am wrong. \$\endgroup\$ Commented Oct 7, 2022 at 13:00
  • \$\begingroup\$ They're lower resistance at DC and higher at other frequencies. Take a look at your diagram, you have by pass capacitors connected to other grounds than the chip they're bypassing. How is that going to work? You've stuck a big resistor and inductor in the loop with your bypassing. \$\endgroup\$ Commented Oct 7, 2022 at 13:16
  • \$\begingroup\$ @user1850479 It is planned to do according to the pins potential. The IN and OUT pins are at 24V and the other pins are at 5V max. thats the reason it has been bypassed in such a way (but have to agree that its not recommended in the datasheet but I have presumed that it should work considering the different voltage levels point. \$\endgroup\$ Commented Oct 10, 2022 at 8:55
  • \$\begingroup\$ I think you are misunderstanding the purpose of bypassing. The goal is to provide a lower inductance return path than the main power circuit (the inductance of which is said to be bypassed). The way you do this is to connect the power and ground pins of the chip with a capacitor that has the smallest possible loop area. If you connect the capacitors in such a way that their inductance is higher than the power lines (for example, by putting an inductor in series as you have done (!!!!)), then they're useless and you have essentially chosen not to use the (required) capacitors. \$\endgroup\$ Commented Oct 10, 2022 at 12:48

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[...] I learnt that the digital (microcontroller), analog (ADC reference) and power lines (For motors) have to have their own seperate areas when it comes to partitioned ground schemes [...]

This is wrong!

The design goal is not the separation of the GND areas, but the separation of the current loops in the circuit. E.g. you do not want the motor current loop get mixed up with the ADC current loop of a sensor.

Separation of GND planes with ferrites (like in your circuit diagram) often leads to bad performance of the circuit. Think about what happens to your circuit if PGnd and AGnd were separated by a potential of e.g. 10 Volts. The ferrites do exactly that: They allow some (RF) current flowing through the ferrites to lift PGnd to another potential than AGnd. That might not be what you want!?

Again: Think of ALL possible current loops and try to (physically) separate the ones that are sensitive to interference.

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  • \$\begingroup\$ " you do not want the motor current loop get mixed up with the ADC current loop of a sensor", But somehow both the motor current return path and the analog return path should get back to the same ground right? so what do you mean by seperating the current loops? and how is it done? and how do they join to return to the same ground (from the source). would you mind if you could please elaborate on this? \$\endgroup\$ Commented Oct 10, 2022 at 8:28
  • \$\begingroup\$ Joining the loops at exactly the right point is known as star grounding. This is another very important technique. \$\endgroup\$ Commented Oct 11, 2022 at 10:04

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