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[Moved] Regarding E1 circuit PCB routing

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Pawan_tej

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I want to do the pcb layout for the 120ohm E1 circuit as mentioned in the attached file.
The 26 ohm differential termination resistor between the Receive Tip and ring is mentioned by the E1 framer(/LIU) manufacturer.

I would like to know the differential trace impedance between the Tip and Ring pairs before and after
the transformer for both transmit and receive.

My understanding is that the differential trace impedance between Tip/Ring pairs connecting the Framer to Transformer should be 26 ohms for both transmit and receive, whereas
the differential trace impedance between the Tip/Ring pairs connecting the Transformer to E1 line side should be 104(26*4) ohms for both transmit and receive.

Is my understanding correct? please clarify.
 

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FvM

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You don't need trace impedance matching for low-speed signals like E1 (2 MB/s) over moderate distances.
 

Pawan_tej

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You don't need trace impedance matching for low-speed signals like E1 (2 MB/s) over moderate distances.
Hi FVM,

Thank you for the reply.
As per the hyperlynx tool simulations, we are getting 22 mil trace width for 26 ohm differential impedance. So as per your suggestion, can I reduce the trace width from 22 mil to 10 mil for 26 ohm differential impedance.

Pawan
 

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It depends on the trace length. You should convert the actual trace impedance into inductance and calculate if the total series inductance has any relevance.
 

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