TS3L501E: Three input sources contact to one RJ45 using TS3L501E to switch them

W.H. Liu

Part Number: TS3L501E
Other Parts Discussed in Thread: DP83867IR, DP83822I

Dear Sir,

We have a application need three input sources to contact one RJ45, the detail describe below:

There are three units where Ethernet PHY IC keeps on motherboard in. And there is one common test board for these three application units, but the contact interfaces on the board were different. 1st one use 2.0mm pitch pin header, 2nd one use 1.27mm pitch pin header, 3th one use 2.0mm pitch pin header with 1.5m cable to contact motherboard.

I found TI Ethernet LAN Switch TS3L501E maybe solve my request, the approach shown below, but I need your confirm.

1. Each CON has two pair of TX/RX differential Ethernet signals, so I use two TS3L501E (U101, U102) to control which one can contact with target RJ45.

2. U102 Port B to link with CON2 ENET_TX2/ENET_RX2, U102 Port C to link with CON3 ENET_TX3/ENET_RX3. And U102 Port A I/O we called ENET_TX23/ENET_RX23.

3. U101 Port B to link with CON1 ENET_TX1/ENET_RX1, U101 Port C to link with ENET_TX23/ENET_RX23. And the U101 Port A I/O connect with Ethernet transformer, X1, and X1 connect with target RJ45.

4. So we will have 4 control pins to determine which CON# can contact target RJ45, [PD1, SEL1, PD2, SEL2], and I would like to use 2x2 pin header to jump each control pin, in order to determine control pin can be pull high or pull low.

My question are:

1. Our Ethernet application is used for 10M/100M/1000M base-T. Does this design can work? CON2 & CON3 contact RJ45 through 2 LAN switch, would it affect the speed range, bandwidth?

2. Especially for CON3 we will use 1.5m ribbon cable, Samtec FFSD, to contact the Unit. Does this design can drive this length? Or I need use another buffer to improve Ethernet signal to keep SI issue?

3. If we use Ethernet PHY, DP83867IR, whether it can push 1.5m length, and two LAN switch without buffer?

4. If we would like to used for 10/100M based-T application, to use Etherent PHY DP83822I, whether it also can drive 1.5m, and two LAN switch without buffer?

5. I saw there was a Q/A mentioned that TS3L501E doesn't need Ethernet transformer, is that truce? If yes, how about for my application? Is it still necessary to keep it?

Thanks

David

over 5 years ago

0 Rami Mooti1 over 5 years ago

TI__Mastermind 35638 points

David,

I'm not quite following the diagram you're explaining. Could you send me a block diagram or schematic of what you're trying to implement so I can better confirm if it will work?

With regards to the questions:

Truthfully, i'm not an expert in ethernet design so I can't comfortably and confidently give you design tips and tell you whether a 1.5m ribbon would require a buffer or not. I can tell you about the the switch itself though. It typically won't have much impact on the signals and adding it in the circuit won't require any added transformer or extra circuitry to mitigate its effects. Additionally the device also has no drive capability so whether it can drive 1.5m isn't dependent on the switch. It's a FET switch so as long as the signals are within the recommended operating condition, they should be fine.
The technical aspects of the actual ethernet connection may be something better to ask the data converter forum

Additonally, here's a resource that may be useful
https://e2e.ti.com/support/switches-multiplexers/f/388/t/702185

Thanks,
Rami Mooti

0 W.H. Liu over 5 years ago in reply to Rami Mooti1

Intellectual 325 points

Hi Rami,

Thanks for your reply. I update the diagram for my application.

Multiple Ethernet Soures Using TI Ethernet MUX_DEMUX application.pdf

David

0 Rami Mooti1 over 5 years ago in reply to W.H. Liu

TI__Mastermind 35638 points

Hey David,

When cascading devices, you'll have double the insertion loss. So the 600MHz bandwidth dips down to ~300MHz. This should be fine for the fastest 1000 base T requires 62.5MHz per line. Although i'm curious how you're doing this with just two lines. 1000base T requires 4, if i'm not mistaken, from the typical applications i've seen.
Given that typically it's recommended to go 3x for the BW requirements so 62.5x3 ~= 190MHz so the insertion loss shouldn't be much of a problem so you won't need to redrive the signal here. Just something to keep in mind as you're designing and if you try to integrate more TS3L501E in series.

Thanks,
Rami Mooti

0 W.H. Liu over 5 years ago in reply to Rami Mooti1

Intellectual 325 points

Hi Rami,

Thanks for your reply.

Yes, you are right, for 1000base T requires 4 lines, diagram just simply show the connection approach.

Based on your recommendation,

1. for the fastest 1000 base T requires 62.5MHz per line.

2. 3x for the BW requirements so 62.5x3 ~= 190MHz

>> Does that mean the 600MHz bandwidth of TS3L501E is per line of Ethernet Signal?

>> for the 100 base T, how much bandwidth is necessary per line?

David

0 Rami Mooti1 over 5 years ago in reply to W.H. Liu

TI__Mastermind 35638 points

David,

1) Yes the 600MHz is the perline bandwidth of the device so this should be more than enough for your use case.

2) 100 base T has a data transfer rate of 100MHz that is accomplished through 2 wire pairs. Each of these pairs can send a symbol at the positive and negative peak of a cycle. And 100MHz is what the end goal for 100Base T. Given this we can do some quick math 100MHz/4lines (2 pairs) /2 symbols per cycle per line = 12.5MHz.
So this will be the per line bandwidth for 100Base T.
This can be done for 1000Base T. 1000MHz/ 8 lines (4 pairs) / 2 symbols per cycle per line = 62.5 MHz.

Hope this helps!
Rami

0 W.H. Liu over 5 years ago in reply to Rami Mooti1

Intellectual 325 points

Hi Rami,

Thanks for your reply. I appreciate your clear explanation, that is very helpful to me.

David

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TS3L501E: Three input sources contact to one RJ45 using TS3L501E to switch them