TS3L110 LAN SWITCH application

Jeff,

Can you describe the damage you are seeing with the TS3L110?  What are the symptoms of the failure.

The TS3L110 recommended operating conditions states the input voltage to 0V to 5.5 V.  Is the TS3L110 subject to a negative voltage or in excess of 5.5V? 

Thank you,

Adam

Hi Adam,
Thank you for your reply.
When it failure,some of the ports of IX or YX may be damaged,the impedence between IX and GND or YX and GND may be 10Ω ~1.5kΩ.

Because of the TX and RX are differential singals, and is isolation from the system,so I think the singal is floating to GND, but when I measure the voltage from TX or RX singal to Gnd, there may be have a voltage of 3.3V not excess of 5.5V, but I am not sure whether the voltage excess of 5.5V when it is damaged.

Hi Adam,
Have you found the problem and give me some suggests about my design?

Jeff,

Yes, I believe you problem to be the voltage the TS3L110 is experiencing are outside of the recommended operating conditions.  The magnetics in the Ethernet chain are isolating the AC signal and the TS3L110 is experiencing a negative voltage swing without the proper common mode voltage.  I know I have run across a document showing how the common mode voltages are used off the transformers in Ethernet applications but I cannot find it at the moment. 

I am moving this thread to the Ethernet forum for some guidance on how to implement the Ethernet interface to keep the TS3L110 from being damaged by the negative voltage swing.

Thank you,

Adam  

Adam,

I may add  Signal Schottky Diodes to the ports of TX and RX to clamp the common voltage as follow,so the max and min voltage of ports may be -0.4~3.7V ,not exceed the limit voltage to  protect TS3l110, how do you think?

Thank you.