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analogLib

itos

... is so frustrating!

Always some crazy thing that's just random!

Today: vccs ignores ggain.

This is a very simple test circuit showing the nodes voltages (R=1):

As clearly can be seen, the transconductance is set to -0.1! But the netlist just always contains gm=1:

// Generated for: spectre
// Generated on: Oct 14 19:43:17 2015
// Design library name: playground
// Design cell name: test_vccs
// Design view name: schematic
simulator lang=spectre
global 0
include "models.scs"
include "nominal/spectre/nominalwrapper.scs"

// Library name: playground
// Cell name: test_vccs
// View name: schematic
G0 (net3 0 net2 0) vccs gm=1.0
R0 (net3 0) resistor r=1
V0 (net2 0) vsource dc=1 type=dc
simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \
    tnom=25 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \
    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
    checklimitdest=psf
dcOp dc write="spectre.dc" maxiters=150 maxsteps=10000 annotate=status
dcOpInfo info what=oppoint where=rawfile
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
saveOptions options save=allpub subcktprobelvl=2

My PDK by default uses Eldo as simulator but also supports spectre (which I want to use!) The cds.lib which my PDK created contains:

DEFINE basic $CDSHOME/tools/dfII/etc/cdslib/basic
DEFINE analogLib $CDSHOME/tools/dfII/etc/cdslib/artist/analogLib
[...]
UNDEFINE analogLib
DEFINE analogLib $MGC_AMS_HOME/data/cdslib/615/analogLib

What the heck are the MGC_AMS_HOME versions and what the CDSHOME versions and why are they forcibly overridden?

Anyway, I thought maybe it's because eldo so I uncommented the MGC_AMS_VERSION so that the version in $CDSHOME/tools/dfII/etc/cdslib/artist/analogLib is used (this is also seen in the Library Manager).

So changes.

What is the correct analogLib that should always be used and where do all these problems come from? (I had many similar already, e.g. recently ideal_balun did not work in Eldo and here was another problem )


Thanks

itos

  • Itos,

    My guess is that this is the Mentor customised version of analogLib getting in the way again. It's quite possible that they use a different parameter for transconductance than is used for spectre. So first check in the schematic editor under Options->Tool Filter that spectre is enabled (and perhaps eldoD is turned off) to ensure that the property editor and property assistant are showing you parameters that are used for spectre - otherwise it might be showing you just parameters used for eldoD which might mean you're entering an irrelevant parameter.

    I just tried this with the $CDSHOME version of analogLib and it works fine for me. In general I believe that Mentor just add their additional information to a copy of our analogLib in order to support Eldo - if it breaks something, you should take this up with them.

    BTW, if you changed the version of analogLib that was picked up, you might also need to do a Netlist->Recreate to force it to renetlist using the other version. Also, you should do a File->Refresh in the CIW to make sure the CDF is refreshed if you do this change during an open Virtuoso session.

    Regards,

    Andrew.

  • Hi Andrew,

    Thank you!

    This is so weird but after many hours of debugging I got it working: It is independent of the path and/or version of analogLib! My PDK added this line to .cdsinit which pretty much destroyed everything (probably for hspice supprt):

    ; HSPICE setup
    load( strcat(getShellEnvVar("HSP_ADE_INTEG_HOME") "/HSPICE.ile"))

    After commenting it out it worked - both Mentor and Cadence analogLib! I really wonder why nobody using the PDK run into trouble before ...

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