Re: [SI-LIST] : transmission line theory

Stephen Peters (sjpeters@ichips.intel.com)
Tue, 03 Mar 1998 09:54:58 -0800

Hello Andrew:

The best practical introduction to transmission lines in
a digital environment I've ever found is the Motorola 'MECL System
Design Handbook' by William Blood. I'm pretty sure it's still available.
Start with chapter 3, then work you way thru chapters four and seven. A
copy of the Fairchild F100K ECL users handbook that would a plus, but I
think that one is out of print. Anyways, happy reading....

Regards,
Stephen Peters
Intel Corp.

> Hi All,
>
> I am interested in transmission line theory as suggested by Mark
> below. Does anyone have suggested references both basic and
> intermediate?
>
> Thanks
> Andrew Bodley
> andrew.bodley@intel.com
>
> > I find it necessary to go back to transmission
> >line theory (reflection coefficients, etc.) and make sure what
> I'm
> >simulating makes sense!
>
>
>
> > -----Original Message-----
> > From: Greg Edlund [SMTP:Greg.Edlund@digital.com]
> > Sent: Tuesday, March 03, 1998 5:06 AM
> > To: 'Mark Nass'
> > Cc: 'si-list@silab.eng.sun.com'
> > Subject: RE: [SI-LIST] : Driver Strength
> >
> > Mark,
> >
> > I have found that driver current ratings don't mean a whole lot today.
> > They are a hold-over from TTL days, when each receiver drew a certain
> > dc
> > current and a driver had to be able to source the dc current of all
> > its
> > loads. In a CMOS environment, they are useful in a relative sense,
> > i.e.
> > you can guess that a 4 mA driver will probably have a lower output
> > impedance than a 2 mA driver - within the same part family and the
> > same
> > vendor. However, don't expect vendor A's 4 mA driver to have the same
> > output impedance as vendor B's 4 mA driver.
> >
> > Output impedance tends to be a much more useful parameter in a
> > transmission line environment. Unfortunately, most vendors don't spec
> > output impedance. If you have a non-linear output IV curve, it does
> > vary over loading, making it a little difficult to spec. The vendor
> > would have to guess what kind of environment driver will see and spec,
> > say, a 60 Ohm resistive load to ground and Vdd. Even this information
> > is more useful than nothing.
> >
> > The best thing you can do is to ask for an IBIS model of your driver
> > that is verified against lab data.
> >
> > How many loads you can expect to drive varies widely with load
> > capacitance, net topology, and timing. A behavioral simulator is an
> > excellent tool for prototyping nets and answering these kinds of
> > questions. It's important not to rely on the simulator to do all your
> > work for you, though. I find it necessary to go back to transmission
> > line theory (reflection coefficients, etc.) and make sure what I'm
> > simulating makes sense!
> >
> > ----------
> > Greg Edlund, Principal Engineer
> > Server Product Development
> > Digital Equipment Corp.
> > 129 Parker St. PKO3-1/20C
> > Maynard, MA 01754
> > (978) 493-4157 voice
> > (978) 493-0941 FAX
> > greg.edlund@digital.com
> >
> > ----------
> > From: Mark Nass[SMTP:markn@rccorp.com]
> > Sent: Monday, March 02, 1998 10:35 PM
> > To: si-list@silab.Eng.Sun.COM
> > Subject: [SI-LIST] : Driver Strength
> >
> > Can someone explain to me what driver strength means? When
> > a driver is spec'd by an ASIC vendor as a 12ma, 6ma, etc what
> > does
> > that mean as far as its expected VI curve and how many loads
> > I can expect it to drive?
> >
> > Thanks,
> > Mark Nass