I have a USB3318C phy, I would like to isolate the digital signals between the phy and the microprocessor the interface at the full 480MPbs. How could I provide galvanic isolation on the UPLI interface?

The UPLI interface runs at 60MHz, it has 8 Data lines that can be bidirectional. So, Gavanic isolation on a 60MHz bus.

  • \$\begingroup\$ I believe, there are dedicated ICs for USB isolation. \$\endgroup\$
    – Sim Son
    Nov 6, 2020 at 19:24
  • \$\begingroup\$ Not for USB 2.0 High speed, if you want the full 480Mbps there are no isolators that work at that speed. All of the isolators available use a scheme like this PHY<->FPGA<->Digital isolator<->FPGA<->PHY. I want to do this UPROC<->Isolator <->Phy \$\endgroup\$
    – Voltage Spike
    Nov 6, 2020 at 19:34
  • \$\begingroup\$ Why isolate the complicated 8 data line bus instead of the pseudodifferential single lane USB2.0? Gut feeling:if you didn't find an IC, the "simplest" solution might be detangling the bidirectional bus with an FPGA on both sides of the isolation... \$\endgroup\$ Nov 6, 2020 at 21:01
  • \$\begingroup\$ No, because I don't have that topology, you can isolate the phy and the UPLI interface, how do you isolate a bidrectional bus? \$\endgroup\$
    – Voltage Spike
    Nov 6, 2020 at 22:44
  • 1
    \$\begingroup\$ "how do you isolate a bidrectional bus?" You spit the bus into two unidirectional ones, just as you already mentioned, {FPGA<->Digital isolator<->FPGA}. ULPI turn-around times might be a problem though. \$\endgroup\$ Nov 14, 2020 at 6:44

1 Answer 1


The best way I found is to use ADUM120N (or there are others that are wider than two signals.)

enter image description here
Source: https://www.analog.com/media/en/technical-documentation/data-sheets/ADuM120N_121N.pdf

You need a lot of them for the 14 signals on the UPLI bus (at least 7 if your running the ADUM120. But they get the job done.

They run at 150Mbps with a ~7ns propagation delay time (which is more than suitable for 60MHz.

  • \$\begingroup\$ There are some nice 6-channel ones (e.g. Silabs SI8661BB-B-IU), so two 6-ways and a 2-way (or three 6's with signals to spare) should do nicely. \$\endgroup\$ Jun 9, 2021 at 22:24
  • \$\begingroup\$ Yeah, analog has a few also, but I don't have those in my library (yet). The SI ones are good to know about \$\endgroup\$
    – Voltage Spike
    Jun 9, 2021 at 22:24
  • \$\begingroup\$ If you use Eagle, here's my Silicon labs library with some of the isolators in it. \$\endgroup\$ Jun 9, 2021 at 22:27
  • \$\begingroup\$ Sadly I mainly use altium, but I do use Eagle at home on occasion so I'll look into that. \$\endgroup\$
    – Voltage Spike
    Jun 9, 2021 at 22:28

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