Ron, So your all set to go. Just drive the twisted pair and terminate at the far end with a differential terminator (dependent on your T-line impedance). Since your driving from one board to the next you might have to watch out for common mode differences between driver and receiver. The HSTL specification is 0.68V-0.9V input common mode range for the receiver. This is narrow. Due to ground mismatch on the separate boards you may drift outside of this narrow specification. On the other hand if the HSTL designer has designed a much wider tolerance to common mode variation (due to architecture choice) you may not have to worry about common mode range. The LVDS spec is a lot better on the common mode range. It is from 0-2.4V. Effectively the power supply range. -------------------------------------------------------------- | Bill Cohen | Toshiba America Electronic Components, Circuit Design Group | email: wcohen@xxxxxxxx | office: (508) 486-1031 fax: (508) 481-8828 -------------------------------------------------------------- "Ron Mancuso" <ron.mancuso@co To: <Bill.Cohen@xxxxxxxxxxxxxxxx> rrent.com> cc: Subject: RE: [SI-LIST] HSTL Buffer 02/20/02 07:39 PM Can't choose. The other board is designed by another company - I have to interface to it. The ASIC I have to use, also uses HSTL - can't change that either. Also, by the way, these are neither Class I or II, but differential HSTL which eliminates the need for a reference voltage. Thanks, Ron -----Original Message----- From: Bill.Cohen@xxxxxxxxxxxxxxxx [mailto:Bill.Cohen@xxxxxxxxxxxxxxxx] Sent: Wednesday, February 20, 2002 4:18 PM To: Ron Mancuso Cc: si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx Subject: Re: [SI-LIST] HSTL Buffer Ron, I have designed HSTL class I & II HSTL buffers. While the receiver is technically differential the signalling is really single ended with a reference signal. The termination is designed for either far end or near and far end (Class I/II differences). I would think LVDS would be a much better choice. I have seen several ads in tech journals for standard LVDS driver and receivers. LVDS can be terminated on the far end using differential termination (not tied to a reference). -------------------------------------------------------------- | Bill Cohen | Toshiba America Electronic Components, Circuit Design Group | email: wcohen@xxxxxxxx | office: (508) 486-1031 fax: (508) 481-8828 -------------------------------------------------------------- I'm looking at an application where differential HSTL is run from board to board via twisted shielded pair. I'm investigating the option of possibly adding buffers to strengthen the signals both as they leave and enter the board I'm designing. Any tips on how to do this or parts that can do this? Also, I'm assuming that since this is differential signaling, I wouldn't need the VTT terminator - but I would rather be wrong now than later. :) Any input would be appreciated. Thank you, Ron Mancuso Corrent Corporation ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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