RE: [SI-LIST] : [SI-LIST] Positive ECL (PECL) voltage swings, but

Krull, Nick J (KrullNJ@LOUISVILLE.STORTEK.COM)
Thu, 29 Jul 1999 13:00:15 -0600

Another reason that the signals are AC coupled is that on the other side of
the cap their may be
a receiver with its own reference voltage. If one terminates at the
receiver input to that reference,
the incoming signal is optimally centered for the receiver.
Nick Krull, Applied Electronics

> ----------
> From: Salvador Aguinaga[SMTP:Salvador_Aguinaga@mw.3com.com]
> Sent: Thursday, July 29, 1999 10:28 AM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : [SI-LIST] Positive ECL (PECL) voltage swings,
> but designed to be AC coupled
>
> <<File: ATT199432.txt>>
>
>
>
> All,
>
> Will some one shed some light on why differential lines (to and from) a
> ECL
> device are AC coupled? I've been unsuccessful at finding an answer from
> my
> internet searches.
>
> I am speaking specifically to the AC coupling that is found in
> fibre-channel
> ser-des transmitters.
>
> (P)ECL C1
> |\-------------o-----||---
> | \ |
> | / | C2
> |/o------o-----------||---
> | |
> | |
> < R1 >R2
> > <
> | |
> | |
> _|_ _|_
> GND GND
>
> Where C1=C1=0.01uF
>
> Why is the capacitor needed? What is the theory behind this
> implementation?
>
> Thanks,
>
> --------------------------------------------------------
> _ __ Salvador Aguinaga Jr.
> /_/ )/ _| Carrier Systems Group
>

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****