I'm trying to design my own USB 3.0 hub based on this commercial design,

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I can understand everything in this design except the usage of IC "ASM1543". Unfortunately there is no datasheet available, however a product brief is available at https://www.asmedia.com.tw/product/85ayqa4SX4XSewIf/230yQc0rgeGp9TJ4 According to the brief this IC is a,

ASM1543 is a one Four to two differential channels mux switch with integrated Type-C 
Configuration Channel Logic Circuitry, using for USB3.1 type-C mux and CC detection

The IC looks like to be connected between USB 3.0 hub IC and USB C port. I wish to have a USB C connection on my design. Yet I'm confused if I should use this IC. Since there is no datasheet available I prefer to avoid using it if it's not necessary.

My question is what is the purpose of this IC? Would I have proper USB C functionality without using this IC by directly connecting a USB C port to bridge IC? After all as per my understanding USB C is only a form factor. Technically I don't need any soft of circuitry to convert USB 3.0 Type A to Type C?

  • \$\begingroup\$ TUSB542 is another example of USB-C MUX. \$\endgroup\$
    – KFE
    Jan 23, 2021 at 9:14

1 Answer 1


You need the mux to handle the case of plugging in the USB-C cable in either direction. The super speed pin pairs are only wired to one side of the connector, so your circuitry must figure out which way it is plugged in and set the multiplexer accordingly.

Another mux you can use is the OnSemi NL3HS3124A https://www.onsemi.com/pub/Collateral/NL3HS3124A-D.PDF

If you don't need super speed (3.0) then you can ignore those pins and don't need the mux, but you'll only get USB2.0 data rates.

  • \$\begingroup\$ Fantastic! This is the answer I wanted. Thank you! \$\endgroup\$
    – Anuradha
    Jan 23, 2021 at 3:37
  • \$\begingroup\$ You can buy a USB 3 hub for less then $5.00, why not buy one and cannibalize the PCB which would already be assembled and tested. If this is a commercial endeavor you have copyrights etc to check before you copy it. \$\endgroup\$
    – Gil
    Jan 23, 2021 at 3:40
  • \$\begingroup\$ @Gil I'm actually using this design for understanding how USB C needs to be handled. There is an open source project available for GL3520 USB hub. I'm heavily designing based on that. This one is just for reference. \$\endgroup\$
    – Anuradha
    Jan 23, 2021 at 3:45
  • \$\begingroup\$ I guess TMUXHS4212 ti.com/lit/ds/symlink/… will also be compatible ? \$\endgroup\$
    – Anuradha
    Jan 23, 2021 at 3:56
  • \$\begingroup\$ That TI part looks fine but I've never used it. I can vouch for the OnSemi part. I can also advise against using the Diodes Inc PI3USB302-A. \$\endgroup\$
    – td127
    Jan 23, 2021 at 17:42

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