TS3L501E: I need to connect the system GND to PE

Hello Ke,

Can you please explain what do you mean by: "I need to connect the system GND to PE before TS3L501E can work"? I am quite confused of what is the issue, what is being disconnected? 

Please elaborate on the application and the mux use case.

Thanks,

Nir 

1，The TS3L501E is in an abnormal operating state，the Resistance between An to Bn is 2000 ohms；

2，When we connect GND to Protect Earth（such as the metal casing of the power source），TS3L501E is OK and the Res. between An to Bn is 1.6ohms；

3，For the Layout example，When we layout my HUB，I connect one VDD（Pin39） to Power supply only。

Hello Ke,

What is the state of the device when you see the resistance of 2000 ohms. Meaning what are the voltage signals on the supply and inputs?

What is the ground of the device connected to during the abnormal operating state ?  

Thanks,

Nir 

I am not good at Ethernet，So，how can I measure the Ethernet signals? like this?

a).Other system Enthernet signals,Its work good:

b). Ts3L501E  Ethernet signals,Its can not work:

DO I need to add a forword bias circute at the input of TS3L501E?

Hi Ke,

I can help here since nir will be OoO the next couple of days.

To continue what nir was saying it looks as if when you connect GND to "protect Earth" the on resistance is normal and within datasheet parameters.

Floating supplies are not recommended for Ti analog multiplexers to operate properly and I would recommended keeping this device GND connected to "Protect Earth" if that is producing the proper operation.

In addition the multiplexer can pass signals within 0v to VDD. The max VDD is 3.6V so you can pass signals through this device from 0V to 3.6V when the device is powered VDD=3.6V

If the signals you are trying to pass through the multiplexer are outside 0V to VDD then you will need to do some kind of DC biasing on the input of the TS3L501E

Are you trying to pass signals that have negative values through the multiplexer?

Regards,

kameron

Usually，the GND of the power supply is not connected to the PE. So," Floating supplies are not recommended for Ti analog multiplexers to operate properly" this means I must connected them？ Are these mentioned in datasheet？

Does this means that Its necessary working conditions are GND connect to PE ？    When I disconnect them ，will they definitely not work properly？

Hi Ke,

The datasheet does mention that the operation of this device and voltages that can be put on the device are with respect to ground.

(This is under the abs max section of the datasheet.)

For this multiplexer and other ti analog multiplexers the grounds pin cannot be floating and must have a reliable connection.

If the ground pin is not connected to gnd the operation of the multiplexer can be incorrect.

For you use case it looks as if connect the GND pin of the mux to PE provides correct grounding of the multiplexer and I recommended to keep doing this.

Finally if you disconnect the GND pin of the multiplexer from (GND/PE) then the operation cannot be guarantee and will not perform as intended

Please let me know if you have any additional questions.

Regards,

kameron

The Grounds pin of TS3L501E had connected to the GND of the system，its not floating. 

The troble is we must connect circut‘s ground plane to the PROTECT EARTH .its not a good idea for my product. If connecting the grounds pin to PE（not GND） is not a necessary working condition，I think there are still issues。

Hi ke,

Please let me know if I am understanding this now.

The TS3L501E Gnd Pin is connected as is always connected to Gnd plane in your system/board/design.

But to get the mux to operate correctly you have to additionally connect the GND plane of your system to PE.

This extra connection is what is setting the device in the correct operating state and giving the proper GND it needs to operate.

I am not a expert on how to design Ethernet systems but i did see where grounding is talked about in this app note.

Is the separation between GND plane in your system and PE due to respect keep out rule?

This might be more of a design question then a multiplexer question but please let me know if I can be of any further assistance

Regards,

Kameron

Hi kameron，

    Is there a demo board's PCB layout could sent me to reference？

Hi ke,

There isn't a pcb layout board I can send to you for this device.

However there are a lot of ethernet and layout  resources from ti that can help you in your system design here.

High speed layout guideline 

TI Precision Lab series-Ethernet

Ethernet Layout

Hopefully this helps!

Regards,

Kameron

Hi kameron，

like this pictrue, we placed TS3L501E between RJ45 and magnetics.maybe there is no correct reference point for TS3L501E and magnetics.when we connect GND to PE,we provide a correct reference plane for them.  another way is we short-circute the cp1 which in under picture,the TS3L501E can operate correctly too.

https://e2echina.ti.com/cfs-file/__key/communityserver-discussions-components-files/60/0083.ts3l100_5F00_LAN-Switch-Application-Clip.pdf

this app note talk about that it should placed between magnetic and PHY