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I am trying to make PCB with W5500 (Ethernet module). I am not finding original supplies so I am looking for alternatives. I did research, and I couldn't find HH-1M1608-12 IJT. I looked at Sparkfun's designs and I found MH2029-300Y but when I read the data sheet they use different values.

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Sparkfun uses the second photo. What I don't understand is how are they choosing right supplies. There is quite a difference. I know if they do that, there must be something. For example, I would choose this:

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The L is using for here (right one Sparkfun's):

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Is this L used for maximizing the power transfer, minimizing signal reflection from the load, or something that I don't know? Also, which L should I use (I don't have HH-1M1608-12 IJT)?

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  • \$\begingroup\$ Thank your for edit @JRE \$\endgroup\$ Oct 21, 2021 at 13:23
  • \$\begingroup\$ The power supply couples to the center tap of the Ethernet transformer, therefore there is coupling of high frequency signals into your power supply and vice versa , the choke is specified to suppress those transients through overwhelming losses and isolate the rest of your digital electronics. The choke is specified such that at low frequencies it behaves as an inductor, at high frequency it looks like a large resistance. Therefore it is to prevent the Ethernet physical layer from presenting an issue. \$\endgroup\$
    – crasic
    Oct 21, 2021 at 13:26
  • \$\begingroup\$ Thank you for explain, which impedance should I use? Should I use MH2029-300Y (Sparkfun's.) \$\endgroup\$ Oct 21, 2021 at 13:34
  • \$\begingroup\$ The only way to say for sure is to see your entire design, If you can't share then I would suggest building and testing several variants, then the trick is , what will you test for? \$\endgroup\$
    – crasic
    Oct 21, 2021 at 13:54
  • \$\begingroup\$ Why are you asking about the right supply without specs and then only discuss the SMT ferrite beads?? The Sparkfun W5500 typically uses < 150 mA but these schematics provide 2A or 3A with beads for some other loads See 5.4 cdn.sparkfun.com/datasheets/Dev/Arduino/Shields/… Do you understand the properties of different ferrite beads? Do you know how to specify current and common mode impedance ? Please state overall power specs and partial power for Ethernet IC then ask to understand what isolation you need before trying to design it.3A vs 150 mA load \$\endgroup\$ Oct 21, 2021 at 13:56

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