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I am a bit confused right now.

I have 2 voltage regulation modules:

The 24V-12V has Vin+, Vin-, Vout+, Vout- while the 24V->5V only has Vin, Vout, GND.

Do I have to use a different ground for the Vin- than for the Vout- and if, which one should I choose for the second regulator? If not, why are there different Vin-/Vout- in the first place?

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  • \$\begingroup\$ What do you understand about V=LdI/dt and traces being about 8nH/cm? \$\endgroup\$ May 10 at 14:49
  • \$\begingroup\$ If a non-isolated converter has sevetal ground wires, they'll all be connected internally. The extra wire is mostly for convenience, so you don't have a wire nut for GND dangling around if you don't need to. \$\endgroup\$
    – bobflux
    May 10 at 17:26
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The feature list on the first page of the datasheet for the 24->12 module states "Non-isolated Module". This indicates that the Vin- and Vout- leads are connected together in the module - the input and output have the same ground.

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Yes, you can connect Vin-, Vout- and GND all to the same ground plane.

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There is no need for separate grounding as these modules are grounded internaly anyway. Vin- and Vout- are the same potential. you can check with multimeter or even by a brisk ogranoleptical means (PCB via check)

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They are two non-isolated voltage regulators and it is not in principle possible to separate the grounds.

However, assuming that +5V supplies logic and potentially susceptible circuits, and +12V more noisy devices, such as a fan, some relays, etc., you might want to achieve some "electromagnetic separation", that means that some disturbance originating from the potentially "dirty" 12V will not couple, eve through the ground.

This can be achieved by putting two inductors in series with the +12V and its 0V, before connecting to the common GND shared with Vin and +5V circuits. Such inductors may be even better a common-mode choke, that would alleviate common mode disturbance, more effectively than using a capacitor that would require an earth reference.

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