[SI-LIST] Injecting noise into a plane
- From: "Alokby, Ahmed" <ahmed.alokby@xxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 16 Jul 2001 14:21:14 -0700
Dear SI subscribers,
I am looking to correlate and quantify the power supply noise that exist on
the VDD pins of a system clock generator to the output clocks cycle to cycle
jitters. I like to be able to induce controlled noise (or ripples) on the
3.3V rail, and directly measure the phase noise. I am sure you all know
there are difficulties in injecting noise from say a function generator
directly into the power plane. To overcome this I think it might be easier
to mock with the power supply it self to generate this noise. (For example
one idea is place a set of power transistors across the rail and gate em
with the desired noise waveform).
Does any one know of a computer power supply that has feature for adding
noise to one of its rails? Or if any one know of a simple modification to a
standard supply that will add controlled ripples to one of the rails? I
would really appreciate any comments or feedback.
Thanks
AA
-----Original Message-----
From: Beal, Weston [mailto:weston_beal@xxxxxxxxxxx]
Sent: Monday, July 16, 2001 1:51 PM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: In EBD model?
Inmyung,
The "Len" parameter specifies the length of a trace segment. Each trace
segment could have different electrical properties so the trace is divided
into many "Len" statements in the path description.
In this case the "Len = 0" represents a via, but in general it simply means
that the L, C, and R are considered lumped instead of distributed. It is
legal to write "Len = 0 R = 50 /" to represent a 50 ohm series resistor.
The units on the parameters are Henries for inductance, Farads for
Capacitance, and Ohms for resistance. The length unit is arbitrary as long
it is the same for all the parameters. I could make up a new length unit
called a stel (it means nothing) and use that unit because it gets cancelled
out in the math.
Len = 2 stel L = 5nH/stel C = 2pF/stel R = 2 Ohm/stel
The impedance of the transmission line segment is:
Z = sqrt(L/C) = sqrt( (5nH/stel)/ (2pF/stel) ) = sqrt( 5nH/2pF )
The length unit went away. Now the delay of the transmission line is
Td = sqrt(LC)*Len = sqrt( (5nH/stel) * (2pF/stel) ) * 2 stel
= sqrt( 5nH * 2pF )/stel * 2 stel = sqrt(5nH*2pF)*2
and again the length unit went away since it was the same unit for all the
parameters. And that is why I love math.
Regards,
Weston
-----Original Message-----
From: Inmyung Song [mailto:imsong@xxxxxxxxxxxxxx]
Sent: Sunday, July 15, 2001 10:37 PM
To: Signal Integrity Mail Group
Subject: [SI-LIST] In EBD model?
Good morning everyone.
In EBD model, the keyword Len is the length of pattern, right?
This IBIS is generated.
[Path Description] /XUPCBD(0)
Pin A6
Len = 0.0414555 L = 2.47486e-007 C = 2.11203e-010 R = 2.56347 /
Len = 0.011303 L = 2.37766e-007 C = 2.5134e-010 R = 2.56347 /
Len = 0.000898026 L = 2.47486e-007 C = 2.11203e-010 R = 2.56347 /
Len = 0.0035921 L = 2.41418e-007 C = 2.57775e-010 R = 2.56347 /
Len = 0.0237123 L = 2.47486e-007 C = 2.11203e-010 R = 2.56347 /
Len = 0 L = 6.03614e-010 C = 2.08724e-013 /
Len = 0 L = 6.03614e-010 C = 2.08724e-013 /
Len = 0.00450031 L = 3.07164e-007 C = 1.22917e-010 R = 5.12693 /
Node U2.54
1. The pattern connected with A6 is routed only Comp and Sold, why the Len
is multiple?
What does it mean?
2. Len = 0, is Via here, right?(The pattern connected with A6 has no
discrete component)
3. L, C, R's dimension is what? nH/inch, pF/inch, ohms/inch? or nH/mm,
pF/mm, ohms/mm?
Any comment is helpful to me.
Thank you for your reading.
Inmyung.
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