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A multi-usb selector by usb switch

x wang
Intellectual 280 points
Other Parts Discussed in Thread: TS3USB3031, TS3USB221

hi all,

i want to make a 1:16 USB selector,one host(PC),16 device(USB storage etc), one host connect on device at a time controlled by MCU. so can i use USB switch chip like tsusb221?

if it is possible,  there are 4 layer:16:8;8:4;4:2;2:1,15 chips. is that OK? if the resistance is too high(4 * Ron)? is there any better choose?

regards,

wang

  • 0
    TI__Genius 9860 points
    You would have to consider the -dB gains of the switches and add them up to find your total signal attenuation at specific frequencies. You can actually use 3 of TS3USB3031 (27 possibilities), which is a 1:3 mux, or use 2 TS3USB3031 and an additional 1:2 mux (18 possibilities).

    The moderator of the Signal Switches forum will be back on January 6 and will be able to provide a more in-depth answer.

    -Ryan
  • 0 in reply to C. Ryan Land
    Intellectual 280 points

    Ryan,

    thanks for replay.

    i have checked the datasheet of ts3usb3031. the gains value is roughly,but  less then -1 DB, so i can use 3 level (27 channel),right?

    regard,

    wang

  • 0 in reply to x wang
    TI__Mastermind 45420 points
    Wang,

    You will have to account for the -1 dB loss through all three of the switches in series. If the total losses of the switches <-3dB loss is acceptable in your system you may use the ts3usb3031.


    Thank you,
    Adam
  • 0 in reply to Adam Torma
    Prodigy 140 points

    Hi,

    I have exactly the same question, although I use TS3USB221 and my intention is not to build 16:1 multiplexer. How should I roughly calculate if this is going to work. I have a USB connection on the PCB which is max. 5cm in length. I don't think one can just easily sum the attenuation of the single switch because the next level loads the previous one. So when I simulate something like this:

    The frequency response is like this:

    So, the actual bandwidth is just slightly over 300 MHz, plus the pulses in time domain are pretty bad. I have found that for Full Speed USB a bandwidth of 240 MHz is needed.

    What else should I take into consideration in order to be able to make a decision if this circuit is possible or not to carry USB signals.

    Cheers and thanx