Slew rate and drive strength are related for sure, but you need to know what load the driver sees in order to determine the driven waveform shape. Slew rate turns out to be dV/dt with the drive strength charging up the load that the driver sees. For example, with IBIS, drive strength is defined with an I/V curve, meaning the amound of current that the driver is capable of delivering at each possible voltage level of the I/O pin. At a given voltage R=V/I shows the output impedance of the driver. Also, the rise/fall wave defined in IBIS shows how the driver would behave if it were driving predefined load. I recommend using a simulator to find the relationship between slew rate and drive strength. However, if you want a simple approximation, make an infinite strength driver (Vpulse in spice) and use the series output impedance. Model the load with a Tline segment loaded with a receiver input. This will give you a rough approximation of rise time. Hope this helps, James R. Jones Dell -----Original Message----- From: Lin Wee [mailto:linwee70@xxxxxxxxx] Sent: Wednesday, September 25, 2002 1:18 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] slew rate and driver impedance Hello: Is there a relationship b/w slew rate & output impedance of the driver ? Can a driver(FPGA) with two different slew rate options have the same output impedance ? Thanks; Lin __________________________________________________ Do you Yahoo!? New DSL Internet Access from SBC & Yahoo! http://sbc.yahoo.com ------------------------------------------------------------------ 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