From: D. C. Sessions ([email protected])
Date: Fri Mar 09 2001 - 10:00:32 PST
On Friday 09 March 2001 10:22, DORIN OPREA wrote:
# # Not Found
#
# The requested URL /~sessions/SLVS-400-pdf was not found on this server.
#
# Can you help it ?
That should have been http://www.primenet.com/~sessions/SLVS-400.pdf
# "D. C. Sessions" wrote:
#
# > On Monday 05 March 2001 21:32, John Lipsius wrote:
# > # Hello,
# > #
# > # I'm interested in how one might judge one superior to the other due to
# > # something inherent. Or, is it board layout, path discontinuities, and
# > # environmental factors that are the only determinant.
# > #
# > # Assume identical 50 ohm and pcb environments, etcetera. And, the
# > # same rcvr type as the driver (no level shifting).
# > #
# > # For example: "assuring no skew between wires of the pair is more
# > # important than any factor inherent to CML vs. LVDS" might be one
# > # answer.
# > #
# > # 1. An initial question is: why is CML offered when there's LVDS ?
# > # (Just a switching capability difference?)
# >
# > For a few reasons:
# > 1) CML is trivial in bipolar, LVDS is much less so since it requires both
# > sourcing and sinking current along with crossover management.
# > 2) LVDS is tricky at best to implement in advanced CMOS processes,
# > since the 2.4 V common-mode range is lethal to small-geometry
# > (read high-performance) transistors.
# > 3) LVDS has problems with crossover between receiver sections. The
# > common-mode range is wide enough that both P- and N-channel
# > input differential receivers are required, with the two outputs mixed.
# > Obviously, this has an impact on receiver performance.
# > 4) LVDS floats the receiver termination, which makes for high CM
# > reflection coefficients.
# > 5) CML is easily implemented in minimum geometry NMOS transistors at
# > core supply potentials, which means no added power supply just to run
# > the I/O.
# >
# > All in all, the only advantages that LVDS has over CML are its superior
# > tolerance for ground shift and independence of power-supply potential.
# >
# > # 3. Lastly, ANYONE KNOW OF SOME CLEAR REF. SOURCES ON CML regarding
# > # both ac/dc specs and these issues for real links? Apparently, there's
# > # no 'standard' version of CML, correct. The web appears completely dry.
# >
# > There's been some interest shown in creating a JEDEC standard CML specification.
# >
# > Personally, I prefer SLVS (http://www.primenet.com/~sessions/SLVS-400-pdf)
# >
# > --
# > | The race is not always to the swift, nor the battle to the strong. |
# > | Because the slow, feeble old codgers like me cheat. |
# > +--------------- D. C. Sessions <[email protected]> --------------+
# >
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#
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-- | I'm old enough that I don't have to pretend to be grown up.| +----------- D. C. Sessions <[email protected]> ----------+**** To unsubscribe from si-list or si-list-digest: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****
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