How to do parallel termination for ethernet controller?

[buenos]

hi

when we use ethernet controllers, and connect them to the magnetics (built into the connector), we have to use parallel terminations on both, RX and TX pairs.

-Where is the location of them? At the receiver end? I think it makes sense only there. Not at the source end of the trace. In a design guide from Realtek, they say, i have to put them to the source end. Is it a mistake? Or i dont know something? So, then, where?

-terminating to ground, or to AVCC? i found reference designs, for both. whats the difference? Does it depend on the controller?

 

[deepak_manikandan]

Re: Ethernet termination

u can terminate at the source end as well as in receiver end,but it depends on application

 

[buenos]

Ethernet termination

but parallel termination at the source?
i use serial termination at the source and parallel at the receiver-end in other applications, not ethernet.

 

[xxargs]

Re: Ethernet termination

but parallel termination at the source?
i use serial termination at the source and parallel at the receiver-end in other applications, not ethernet.

Is depend of type of output driver.

If low impedance voltage source (simular OP-amp output) using serial termination to rise impedance.

If high impedance current source (drive via transistors in current mode - not satturated or current mirror) using parallell termination to lower impedance.

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Most case is low impedance voltage driver and need serial termination and high impedance recivers and need parallell termination.

 

[buenos]

Ethernet termination

at other manufacturers, they recommend the termination at the receiving-end. (SMSC, CirrusLogic)

 

[Iouri]

Ethernet termination

Manufactories (Intel, Cirrus Logic SMSC and etc..) are recomeding magnectics and termination schematics check there app notes and data sheets

 

[buenos]

Ethernet termination

ok. i see. there are not ultimate solutions, or the manufacturers dont provide info to chose myself, i have to use what they chose.