FreeLists / si-list / [SI-LIST] Re: high speed test measurement equipment?

["Sanchez, Louis" <louis.sanchez@xxxxxxxxx>]

Scope bandwidth required, is also based on how much error you are willing to
accept when measuring the rise time on the scope. Using a factor of either 3
or 5 is a good rule of thumb. The rise time observed on the scope is the
root sum square of the scope rise time, probe rise time, and the rise time
of the waveform under observation. Given a permissable % or error in
measured risetime, and a particular probes risetime, then the root sum
square relationship can be massaged to yield the minimum scope bandwidth. I
have used a Mathcad worksheet to graph percentage of error as a function of
scope bandwidth. This proved useful in helping us to evaluate our
requirements prior to purchasing.

Although the relationship between the bandwidth of a scope and its
equivalent risetime is expressed by BW=.35/risetime for a 10% to 90%
measurement, the rise time of many high frequency signals are measured from
the 20% to 80% points on the waveform, e.g., LVDS and PECL. Using a single
pole response model, the relationship between bandwidth and risetime becomes
approximately: BW=.22/risetime. I mention this because I think its important
to consider whether the risetime of a pulse is measured using the 10%/90%
method or the 20%/80% method. Particularly if you're performing any analysis
that reduces everything to an equivalent bandwidth.      

-----Original Message-----
From: Dagostino, Tom [mailto:tom_dagostino@xxxxxxxxxxx]
Sent: Wednesday, February 06, 2002 9:31 AM
To: 'jvalle@xxxxxxxxxxxxxxxxxxxxxx'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: high speed test measurement equipment?



Scope bandwidth required is determine by the fastest risetime you need to
observe, look at the IBIS models or SPICE models you have.  Compute the
bandwidth of that risetime (falltime).  For a risetime expressed from 10 to
90% use the equation BW = .35/risetime.  For example a 350 psec risetime
yields a 1 GHz bandwidth.  To properly display this risetime you will need 3
to 5 times the bandwidth in the scope and probe system.  So you need to look
at the bandwidth at the probe tip.  Remember to keep your probe's ground
lead as short as possible.  The scope probe should have minimum loading on
the circuit, less than 1 pF. 

It is impossible for an outsider to tell you what you need.  You need to
look at what signals you are exploring.  Rise/fall times for modern
component range from about 1 nsec to 15 psec which result in bandwidth
requirements from over 1 GHz to way over 30. 

Tom Dagostino
Modeling Manager
Mentor Graphics Corp.
SAS
tom_dagostino@xxxxxxxxxx
503-685-1613


-----Original Message-----
From: Javier del Valle [mailto:jvalle@xxxxxxxxxxxxxxxxxxxxxx]
Sent: Tuesday, February 05, 2002 11:27 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: high speed test measurement equipment?



Thanks for the info but, could someone also tell me which test equipment
models they use for signal integrity?. I mean the oscilloscope should have
500Mhz, 1GHz bandwith or more, and also is it needed a special probes for
signal integrity measurements?.

Thanks a lot again,

Javi
 

-----Mensaje original-----
De: Bob Patel [mailto:whizplayer@xxxxxxxxx]
Enviado el: martes 5 de febrero de 2002 19:22
Para: jvalle@xxxxxxxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Asunto: Re: [SI-LIST] high speed test measurement equipment?


Hi! JAvier, 
Books: 1) High speed digital design- A handbook of
Black magic by Howard Johnson
2)High Speed Digital System Design: Hall Hall McCall
Web sites: 1)www.sigcon.com
2)www.ultracad.com
3)www.dsmith.org
Equipment: I prefer a VNA with built in TDR, this way
you can do both frequency domain & time doamin
measurements--Contact Agilent
Bob
--- Javier del Valle <jvalle@xxxxxxxxxxxxxxxxxxxxxx>
wrote:
> 
> Hi to all,
> 
> I am quite junior at high speed/signal integrity
> design and I would like to
> learn more about it. I have seen some demos of
> programmes like Specctraquest
> and hyperlinx, that some of you use for your
> designs. I would like to know
> also which is the test and measurement equipment
> needed, and the required
> specifications of these equipment for the design of
> boards similar to  PC
> motherboards that integrates microprocessors like
> Pentium IV, PowerPC with
> high speed buses. I also would appreciate if someone
> could recommend me some
> books for learning about how to perform high speed
> measurements, what to
> measure (timing measurements, ...) etc. (I just have
> read a book about this
> field but was not much practical).
> 
> Thanks a lot and best regards,
> 
> Javi 
>
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