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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
Reply to
jai.dhar
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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

Reply to
Don Bowey

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

D> On 6/18/06 9:33 AM, in article

Reply to
jai.dhar

Yes, the physical jack is the same for RJ45 and RJ48C, but the pin assignments differ.

You did not mention the IC you are using or what you are building; whether the interface is DSX-1 or a 30 dB line. The datasheet for the device should give you the insight you require. If this is for a commercial product, I'd follow its recommendation?

Don

Reply to
Don Bowey

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