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Using CD4097B as an 8-way USB 2.0 Multiplexer

Ali Syed19
Prodigy 90 points
Other Parts Discussed in Thread: CD4097B, TS3USB3000, TS3DS10224, SN74CB3Q3251

Hi,

I'm trying to use the CD4097B(PWR) as a 1:8 USB 2.0 multiplexer. Even though it's a differential multiplexer, it doesn't seem to work. Is it even possible with this chip, or are the USB D+ and D- signal too low voltage for this chip to work properly as a USB multiplexer? Could any one provide me any reference designs as to how this would work (Currently I'm doing this on a breadboard; maybe that's my issue). Also, are there any other chips capable of doing 1:8 USB 2.0 (without cascading). I'm looking for a TI chip similar to the MAX4999.

I appreciate your help.

Thank you and best regards,
Ali

  • 0
    TI__Mastermind 45400 points
    Ali,

    The CD4097B does not have enough bandwidth to support USB 2.0 signals. You would need to look at the TS3USB3000 TSeUSBXXXX family of switches to support USB 2.0 applications.

    I couldn't find a device equivalent to the the MAX4999. The closest match to an 1:8 USB 2.0 mux is the TS3DS10224 that can be configured as a 1:4 USB mux. You would need to use 2x TS3DS10224 devices.

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    Prodigy 90 points
    That would explain a lot. What kind of bandwidth would be required to support USB 2.0? Also, is there a reference design for using TS3DS10224 as a USB 2.0 1:4 Mux?

    Thank you for your help.

    Best regards,
    Ali
  • 0 in reply to Ali Syed19
    TI__Mastermind 45400 points

    Ali,

    Please see the FAQ thread question number 2 for the answer to what kind of bandwidth would be required to support USB2.0.  The USB 2.0 standard states max data rate of 480Mbs so ~720MHz is need.

    We are in the middle of updating the datasheet.  Here is a preview of how to configure the device for 1:4 mux

    Let me know if this helps.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Prodigy 90 points

    Hi Adam,

    Thanks for this. However, I had looked at the datasheet and understood how it works. My question was more regarding a hardware reference design, like do I need to add any capacitors, or resistors, etc. of a specific value to specific pins when I'm actually implementing the circuitry for testing or can I do direct digital connections to all of the signal and control lines? Also, for doing a 1:8 using this chip, would it be as simple as branching the USB signals in to INA (or INB) of both chips.

    Thank you for your help.

    Best regards,
    Ali

  • 0
    TI__Guru 58150 points
    Hi Ali ,

    SN74CB3Q3251 is 1:8 Mux which is suitable for USB 2.0 Multiplexing which could be considered as well .
  • 0 in reply to ShreyasRao
    Prodigy 90 points
    Thank you Shreyas. I've ordered some samples, I'll test it out to see if it works.

    Best regards,
    Ali
  • 0
    Prodigy 90 points
    Would either of you know if CD74HC4351E would work?

    Thanks,
    Ali
  • 0 in reply to Ali Syed19
    TI__Guru 58150 points
    Although it is 1:8 Mux , it is bandwidth limited to 180Mhz.
  • 0 in reply to Ali Syed19
    TI__Mastermind 45400 points
    Ali,

    The signal switches do not require any external components to operate so we do not have any reference schematics available. We do recommend placing a bypass capacitor on the supply pins as good practice.

    Yes a two IC solution using the TS3DS10224 as a 1:8 mux would be connecting your USB 2.0 PHY to an input of each IC and then use the GPIOs and truth table to mux the signal accordingly.

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    TI__Mastermind 45400 points
    Shreyas,

    Thank you for the recommendation of other 1:8 mux. My one concern with using the SN74CB3Q3251 is that is not a differential switch. You would still need to have a two IC solution for using one IC for the D+ signal and one for the D-. Do you see any signal integrity issues having the D+ and D- signals going through two different ICs?

    Adam