Additya
Guest
Thu Mar 11, 2010 7:05 pm
Hello friends , I came across a book for Signal Integrity which is
available on internet. Check out
http://www.ezdia.com//Signal-Integrity-for-PCB-Designers/Content.do?id=1435
The complete book will be made available over a period of two weeks.
Joel Koltner
Guest
Thu Mar 11, 2010 7:51 pm
"Additya" <addy.ind_at_gmail.com> wrote in message
news:86c70eaf-2b15-4a4d-b1a6-6a65a06de33f_at_m35g2000prh.googlegroups.com...
Quote:
http://www.ezdia.com//Signal-Integrity-for-PCB-Designers/Content.do?id=1435
From the above:
---
Tom - I was reading this rise time and knee frequency stuff. It says that the
rise time is a significant thing and determines the highest frequency content.
Does it mean that if I have a 1 KHz square wave that has a rise time of 100
ps, it should be treated as a high frequency signal with spectral frequency of
or 3.5 GHz?
Bob - Ideally, yes, this 1 KHz signal should be treated as a 3.5 GHz signal at
least from some of the SI angle, e.g., EMI. But Tom tell me why will anyone
design a circuit with 1 KHz frequency with such a fast rise edge? Does it make
sense? A very fast rising edge makes sense only when you want to achieve high
data rate.
---
Seems like that needs a bit more qualification... more like, "while not too
many applications require super-fast edges but have low repetition rates,
sometimes this will occur..."
John Larkin
Guest
Thu Mar 11, 2010 8:58 pm
On Thu, 11 Mar 2010 10:51:27 -0800, "Joel Koltner"
<zapwireDASHgroups_at_yahoo.com> wrote:
Quote:
"Additya" <addy.ind_at_gmail.com> wrote in message
news:86c70eaf-2b15-4a4d-b1a6-6a65a06de33f_at_m35g2000prh.googlegroups.com...
http://www.ezdia.com//Signal-Integrity-for-PCB-Designers/Content.do?id=1435
From the above:
---
Tom - I was reading this rise time and knee frequency stuff. It says that the
rise time is a significant thing and determines the highest frequency content.
Does it mean that if I have a 1 KHz square wave that has a rise time of 100
ps, it should be treated as a high frequency signal with spectral frequency of
or 3.5 GHz?
Bob - Ideally, yes, this 1 KHz signal should be treated as a 3.5 GHz signal at
least from some of the SI angle, e.g., EMI. But Tom tell me why will anyone
design a circuit with 1 KHz frequency with such a fast rise edge? Does it make
sense? A very fast rising edge makes sense only when you want to achieve high
data rate.
---
Seems like that needs a bit more qualification... more like, "while not too
many applications require super-fast edges but have low repetition rates,
sometimes this will occur..."
3.5 GHz is the 3.5 millionth harmonic of 1 KHz. So the power spectral
density up there will be zilch.
But a fast edge can ring at any frequency, and that could, for
instance, mis-clock a flipflop. So just because a signal is 1 KHz
doesn't mean it's "low frequency" and safe to use in a digital system.
John
Fred Bartoli
Guest
Thu Mar 11, 2010 9:43 pm
John Larkin a écrit :
Quote:
On Thu, 11 Mar 2010 10:51:27 -0800, "Joel Koltner"
zapwireDASHgroups_at_yahoo.com> wrote:
"Additya" <addy.ind_at_gmail.com> wrote in message
news:86c70eaf-2b15-4a4d-b1a6-6a65a06de33f_at_m35g2000prh.googlegroups.com...
http://www.ezdia.com//Signal-Integrity-for-PCB-Designers/Content.do?id=1435
From the above:
---
Tom - I was reading this rise time and knee frequency stuff. It says that the
rise time is a significant thing and determines the highest frequency content.
Does it mean that if I have a 1 KHz square wave that has a rise time of 100
ps, it should be treated as a high frequency signal with spectral frequency of
or 3.5 GHz?
Bob - Ideally, yes, this 1 KHz signal should be treated as a 3.5 GHz signal at
least from some of the SI angle, e.g., EMI. But Tom tell me why will anyone
design a circuit with 1 KHz frequency with such a fast rise edge? Does it make
sense? A very fast rising edge makes sense only when you want to achieve high
data rate.
---
Seems like that needs a bit more qualification... more like, "while not too
many applications require super-fast edges but have low repetition rates,
sometimes this will occur..."
3.5 GHz is the 3.5 millionth harmonic of 1 KHz. So the power spectral
density up there will be zilch.
Let's push it a bit further...
350MHz is still 350Kth harmonic of 1kHz and there's still almost nothing
there. So we can safely ignore this part of the spectrum...
.... and, once provided the signal fundamental frequency is low enough we
can design a rather band limited channel while still achieving fast rise
time.
Cute!
--
Thanks,
Fred.
Joel Koltner
Guest
Thu Mar 11, 2010 10:30 pm
"John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> wrote in message
news:pfiip55lel2963k90umda3cubdhg2bli0o_at_4ax.com...
Quote:
But a fast edge can ring at any frequency, and that could, for
instance, mis-clock a flipflop. So just because a signal is 1 KHz
doesn't mean it's "low frequency" and safe to use in a digital system.
I think that's (sort of) what he's trying to say... it's just that there's
plenty of application for fast pulse generators with lot repetition rates
(e.g., TDR!), where you do need to treat the interconnects as "high speed."
Joerg
Guest
Thu Mar 11, 2010 10:59 pm
Fred Bartoli wrote:
Quote:
John Larkin a écrit :
On Thu, 11 Mar 2010 10:51:27 -0800, "Joel Koltner"
zapwireDASHgroups_at_yahoo.com> wrote:
"Additya" <addy.ind_at_gmail.com> wrote in message
news:86c70eaf-2b15-4a4d-b1a6-6a65a06de33f_at_m35g2000prh.googlegroups.com...
http://www.ezdia.com//Signal-Integrity-for-PCB-Designers/Content.do?id=1435
From the above:
---
Tom - I was reading this rise time and knee frequency stuff. It says
that the rise time is a significant thing and determines the highest
frequency content. Does it mean that if I have a 1 KHz square wave
that has a rise time of 100 ps, it should be treated as a high
frequency signal with spectral frequency of or 3.5 GHz?
Bob - Ideally, yes, this 1 KHz signal should be treated as a 3.5 GHz
signal at least from some of the SI angle, e.g., EMI. But Tom tell me
why will anyone design a circuit with 1 KHz frequency with such a
fast rise edge? Does it make sense? A very fast rising edge makes
sense only when you want to achieve high data rate.
---
Seems like that needs a bit more qualification... more like, "while
not too many applications require super-fast edges but have low
repetition rates, sometimes this will occur..."
3.5 GHz is the 3.5 millionth harmonic of 1 KHz. So the power spectral
density up there will be zilch.
Let's push it a bit further...
350MHz is still 350Kth harmonic of 1kHz and there's still almost nothing
there. So we can safely ignore this part of the spectrum...
... and, once provided the signal fundamental frequency is low enough we
can design a rather band limited channel while still achieving fast rise
time.
Cute!
Even better. Since you have now determined that we no longer need the
range from 350MHz to 3.5GHz we could auction that off and issue revenue
anticipation bonds to plug some pressing holes in the budget. Since the
money will have been spent by the time the auction happens we could
already look at whether the 35kth harmonic is good enough so we can pay
the interest :-)
--
SCNR, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
