Hello SI Gurus I'm working on a design for operation at 2.5GBaud. In modeling the path from a Stratos Lightwave PECL driver to the TLK2501 receiver, I noticed that it is not as clean as in the other direction. After much modelling, I'm convinced that the problem is two-fold. First, the MLC driver is low impedance and must be backmatched--a CML part with internal 50 ohms to Vcc would have been a better choice. The backmatching resistor must be placed as close as possible to the source, but via inductance and driver pin inductance limits how effective this resistor is. Second, and definitely the worst offender, is the fact that the TLK device requires external 50 ohm resistors for the end terminations--this leaves stubs that ring, caused by the inductance and capacitance of the pins, bond wires and input transistors. Three questions: 1) Does anyone have any modelling information (internal pin models, driver characteristics, risetimes, etc.) on the Stratos MLC-25-7-2-TL Optical ATM OC-48 part? I'm using Pspice, but IBIS would be a help. 2) Does anyone know if the CML version offered by Stratos has internal 50 ohms to Vcc? (I haven't had any success getting information from the apps engineer at Stratos). 3) I've been able to control the ringing caused by the pin inductance and input C of the TLK2501 by inserting a perfect 27 ohm resistor in series with the input pin (the 50 ohm terminations are placed on the bottom of the card, with the resistor being placed between the termination via and the input pad on top of the card). The question is, what is the smallest lowest-inductance part that I can use for this purpose? Any help would be greatly appreciated. Richard Ellison Ellison Consulting 214-544-1920 bus 214-544-1924 fax ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu