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Original question:

Which side of magnetics do I place TS3L501E?

TS3L501E: TS3L501E resistance to Ethernet signals + circuit recommendations

Kowalski100
Prodigy 135 points
Part Number: TS3L501E
Other Parts Discussed in Thread: TS5A22362

Hi, 

One of our design circuit uses TS3L501E to switch b/w two Ethernet networks. I have the following questions:

  1. The post here says:  "Yes, driving the ethernet lines while the device is not fully powered will damage the part." Does it mean if no power is applied to IC and if one connect the RJ-45 connector (other end connect to say a router), will the IC get damaged? Similarly is the case if we power down the device via PD pin pulled low.
  2. Our circuit uses 5V MCU. does the following resistor divider circuit can be used to drive SEL and PD pins (to convert from 5v to 3.3v)? The power source of IC is kept at 3.3V.

  • 0
    TI__Mastermind 23453 points

    Thanks for the question! Please see my responses below:

    1)

    The device can be connected on both sides just no signal can be present on either side while the IC is off (VCC = 0V). It's not about whether they're just connected to the RJ-45 or router, the concern is whether they are connected AND applying a signal to the IC while it's not powered up. 

    2) Using this divider for the control inputs to shift the voltage level down to a usable level is fine but unnecessary here. The device can handle up to 5.5V on the control pins (PD and SEL) so you can keep the 5V signal and not use the divider at all

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Prodigy 135 points

    Thanks for the reply.

    1. So signal can be applied while the IC is OFF (not powered up)? That's my main point of worry Pensive

    2. I see the voltage fir SEL pin to be 5.5V max but PD pin ratting is not mentioned. Does the same ratting applies to PD pin?

    3. The post below mentions that The IC doesn't support negative voltages. I want to MUX ethernet signals i.e. one RJ-45 to Two RJ-45. I think ethernet does have negative voltages so is it possible to achieve it with this IC?

    e2e.ti.com/.../ts3l501e-is-it-possible-to-use-ts3l501e-to-mulitplex-signals-on-rj45-cable

  • 0 in reply to Kowalski100
    TI__Expert 8652 points

    Hello,

    Rami is currently out of office so he will respond when he is back either tomorrow or Monday at the latest. 

    Thanks!

    Alex

  • 0 in reply to Kowalski100
    TI__Mastermind 23453 points

    Hello,

    1) Yes when the IC is off, as in the signal channels are unselected, you certainly can apply a signal to that unselected channel. 
    (Although this e2e  here implies that you may even be able to use it when VCC = 0V as well)

    2) Yes, this applies to both SEL and PD pins. 

    3) You will need to bias the signal to a level that the device can support. If you do not intend to bias, we may need to find a mux that can support negative voltages. Typically this will be a dual rail mux (VSS and VDD supplies). While we do have some muxes that can support negative signals with a single positive supply (See TS5A22362) the bandwidth of these device would be an issue as they are sub 20MHz devices. I would recommend biasing the signal if you don't already have a negative rail available. Keep in mind that the signal range after biasing would still need to be between 0 and 3.3V. If this can't be done than a dual rail device would be needed. 

    Thanks,
    Rami