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T1 Transformer Ratios

Hello,

I'm trying to design a circuit with a T1 interface chip, magnetics and
RJ45s. I'm having trouble deciding on which magnetics to use. How do I
determine what the pri:sec ratios should be? Is this dependant on the
T1 interface chip? The datasheet for the interface chip says 1:1 for
RX, and 1:2 for TX, but I was wondering what would happen if I used a
1:2 for RX as well? The reason I ask is because I would like to use the
magnetics from Pulse Engineering that have integrated IC-side
protection, and for some reason, they only come in 1:2 ratios. I was
hoping to gain a better understanding of what determines these ratios.
I know how transformers work in general, but what is it that determines
whether I need a 1:2, 1:1.2 etc...

Thanks,

J
 
D

Don Bowey

Jan 1, 1970
0
Hello,

I'm trying to design a circuit with a T1 interface chip, magnetics and
RJ45s. I'm having trouble deciding on which magnetics to use. How do I
determine what the pri:sec ratios should be? Is this dependant on the
T1 interface chip? The datasheet for the interface chip says 1:1 for
RX, and 1:2 for TX, but I was wondering what would happen if I used a
1:2 for RX as well? The reason I ask is because I would like to use the
magnetics from Pulse Engineering that have integrated IC-side
protection, and for some reason, they only come in 1:2 ratios. I was
hoping to gain a better understanding of what determines these ratios.
I know how transformers work in general, but what is it that determines
whether I need a 1:2, 1:1.2 etc...

Thanks,

J

If by T1 you mean a DS1 rate (1.544 MB/s) then the line impedance is 110
Ohms. Also, RJ48 is the wrong pinout. Use RJ48-C.


Don
 
Thanks for the reply Don..

I thought it was RJ45, but you mentioned RJ48-C. In terms of the
physical jack, they are the same thing, no? As in they are both 8-pin
modular jacks with the same dimensions and orientation for Pin 1?

Regarding line impedance, how does this affect my transformer ratio?
I'm still not sure how to settle on a transformer to use.

J
 
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