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HD3SS3212: What is the correct location for TX decoupling caps for HD3SS3212? Data sheet has conflicting info

traian mitrache
Prodigy 125 points
Part Number: HD3SS3212

I am trying to use HD3SS3212, as a MUX for a USB 3.1 type C port.

On page 13 of the datasheet, Figure 7. AC Coupling Capacitors for USB Type C shows the TX caps  placed between the HD3SS3212 and the connector, on the B/C ports.

But the very next figure Figure 8. Down Facing Port for USB3.1 Type C Connector, shows the caps being placed between the HOST and HD3SS3212, on the A ports

Which one is the correct placement?

  • 0
    TI__Guru**** 177396 points
    Traian

    Assuming common mode voltage is less than 2V, then either one is ok. For Figure 7, HD3SS3212 is biased by the host. For Figure 8, HD3SS3212 is biased by the device. Typically, AC coupling caps are placed between the mux switch and USB connector as shown in Figure 7. Please make sure only one side of mux switch is AC coupled while the other side is DC coupled.

    If common mode voltage is higher than 2V, then you need AC coupling caps on both side of mux switch with resistor biasing network as shown in Figure 6.

    Thanks
    David