TS3L4892: Not getting a 100b link

Martin,

Do you have any more information on what a 100b link is? Do you have a schematic and scope captures of the signals going into and out of the device?

Thank you,
Adam

Adam,

Please see block diagram. 

Regards,

Martin,

Thank you for the diagram that shows that one Ethernet PHY is connecting to two different connectors.

Can you please describe how you are not getting a 100b link? Is this link made successfully without the switch?
What are the scope shots of the waveforms going in and out of the switch?

What are the voltages on the power supply and digital logic pins of the TS3L4892?

Thank you,
Adam

Adam,

The link is successful without the switch. The waveforms are sine wave without the switch and with the switch the wave gets clip, only positive wave. Does TI have any circuitry examples? Do I need to add a transformer on the I/O of the switch and what will the voltage for the center tap?

The voltage for the device is 3.3V. Also, is there a way you can contact me directly?

Thanks

Martin,

The TS3L4892 device recommended operating conditions states the voltage range is 0 V to Vcc. The switch will not pass signals < 0V and is why you are seeing clipping when the voltages reach ~ -0.5 V on the signal path. 

All of our LAN switches have minimum recommended operating voltages of 0V and will have this issue so you will need to provide a common mode voltage. 

Thank you,

Adam

Adam,

The issue is not having transformers on the RJ45 I/O's. Does TI have a block diagram on recommended wiring and what transformers to use?

Thank You,

Adam,

Would this be the best configuration for the TS3L4892? Two Ethernet Magnetic Transformers on PCB1, PCB2 is of the shelf and has its own Ethernet transformers. Please let me know.

Thank You

Adam,
Another question, is it safe for the switch to be power off and have Ethernet lines being driven from the RJ45, external?

Martin,

The TS3L4892 does not have a spec that guarantees isolation like the TS3L501E where it states HiZ when Vdd = 0V and I/O voltage = 3.6 V.  We cannot recommended operating the TS3L4892 without power and voltages on the I/O pins.

Thank you,

Adam

Adam,
So with the TS3L4892 it is not recommended having anything plugged on the RJ45 if there is no power on the PCB?
Thanks

Martin,

The TS3L4892 device doesn't have a spec that will recommend signals on the I/O pins with Vdd = 0V. You will need to use a device with powered off protection like the TS3L501E.

Thank you,
Adam

Adam,
In order to set the power down (PD) mode on the TS3L501E the PD needs to be set high. But what happens if the PCB is off, no power? Do the external Ethernet connections need to be remove?
Thanks