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HD3SS3220: common mode biasing

Shmuel Davis
Expert 2930 points
Part Number: HD3SS3220
Other Parts Discussed in Thread: TUSB320

1. In the data sheet it states : "HD3SS3220 mux does not provide common mode biasing for the channel. Therefore it is required that the device is biased from either side for all active channels. Also note that mux channels are for differential SS signals only. "

Where can I get information on this "common mode biasing for the channel" and "required that the device is biased from either side for all active channels"

2. FOR THE  TUSB320 device : I just found this in the data sheets "If VBUS is guaranteed to be less than 5.5 V, powering the TUSB320 device
through a diode can be implemented" - my device is to be a UFP so the VBUS will be dependant on the PC \ Laptop USB port that I am connecting to - thus how can I guarantee that the VBUS will be less than 5.5V ?

  • 0
    TI__Mastermind 36085 points
    Hello,

    The common mode is commonly provided by the USB transceivers. As you can see it is recommended to have the AC coupling capacitors between the HD3SS3220 and the Type-C connector, that ensures 0 VDC common mode on the connector side, meanwhile the AP side will have the USB3 transceiver common mode.

    Having the TUSB320 in a UFP application and getting power from VBUS must be enough to guarantee the VBUS voltage ratings, as long as the devices is connected to a certified port.

    Regards,
    Diego.
  • 0 in reply to Diego Cortes
    Expert 2930 points

    Dear Diego,

    Thank you for the quick reply. 

    So from your answer is placing the AC coupling capacitor between the  HD3SS3220 and the Type-C connector, fulfil the requirement "Therefore it is required that the device is biased from either side for all active channels" outlined in the data sheet ?

    Regards

    Shmuel