Dear Sir,
(I had asked this question in Switches & multiplexers forum, but they suggest to ask in Data Converters forum. So I copy my question here.)
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
