Subject: RE: [IBIS-Users] How to determine C_comp
From: Muranyi, Arpad (arpad.muranyi@intel.com)
Date: Wed Aug 06 2003 - 13:23:35 PDT
I know of about six methods to measure C_comp:
*RC time constant with a step function
*does not show voltage or frequency dependencies
*Time Domain forced saw tooth voltage
*can provide voltage dependent capacitance curves
*does not show frequency dependence
*TDR technique (Time Domain)
*does not show voltage or frequency dependencies
*Frequency Domain sweep with tank circuit
*can provide voltage dependent capacitance curves
*does not show frequency dependence(?)
*Frequency Domain imaginary current
*can provide voltage and frequency dependent capacitance curves
*shows frequency dependence very well
*Frequency Domain pole/zero method
*See BIRD 79 on IBIS web page for details
Arpad Muranyi
Intel Corporation
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-----Original Message-----
From: erik.van.der.ven@philips.com [mailto:erik.van.der.ven@philips.com]
Sent: Wednesday, August 06, 2003 2:25 AM
To: ibis-users@eda.org
Cc: cor.duijndam@philips.com
Subject: [IBIS-Users] How to determine Ccomp
Dear IBIS collegues,
What is the best way to determine Ccomp?
Basically there are two ways: applying a ramp to the output terminal and calculate Ccomp from the slew-rate, or connecting an inductor to the output and calculate the Ccomp from the resonace frequency.
Which method gives the best results? > always, or application dependent?
How is this done for differential outputs. Outputs like LVDS have internal feedback loops to control the common level. Must something be done with the "other" output? Is the peaking a reliable measure for the value of Ccomp, or may the added inductor shift the poles and zeros of the feedback buffer due this load causing a peaking that is not just the parallel connection of Ccomp and the test inductor?
With kind regards,
Ir. Erik van der Ven
Room DB1032
Business Line Networking Infrastructure
Philips Semiconductors BV
Gerstweg 2
6534 AE Nijmegen
The Netherlands
Phone: +31-24-3534334
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