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Design >> Analog Design >> cadence error while simulating comparator
https://designers-guide.org/forum/YaBB.pl?num=1238534921

Message started by jsun on Mar 31^st, 2009, 2:28pm

Title: cadence error while simulating comparator
Post by jsun on Mar 31^st, 2009, 2:28pm

Hi,

while I simulate comparator, cadence shows the following error, how can I solve it?

************************************************
Transient Analysis `tran': time = (0 s -> 50 ns)
************************************************
Attempt to generate initial guess for DC solver failed.

Notice from spectre during IC analysis, during transient analysis `tran'.
Initial condition computed for node v2 is in error by 13.6221 uV.
Initial condition computed for node v4 is in error by 39.9432 uV.
Further occurrences of this notice will be suppressed.

Important parameter values:
start = 0 s
outputstart = 0 s
stop = 50 ns
step = 50 ps
maxstep = 1 ns
ic = all
skipdc = no
reltol = 1e-03
abstol(I) = 1 pA
abstol(V) = 1 uV
temp = 27 C
tnom = 27 C
tempeffects = all
errpreset = moderate
method = traponly
lteratio = 3.5
relref = sigglobal
cmin = 0 F
gmin = 1 pS
maxrsd = 0 Ohm
mos_method = s
mos_vres = 50 mV

Warning from spectre at time = 16.1903 ps during transient analysis `tran'.
Convergence difficulties resulted in error requirements being unsatisfied.
Warning from spectre at time = 220.516 ps during transient analysis `tran'.
T10: Vgd has exceeded the oxide breakdown voltage of `vbox' = 1.6 V.
Warning from spectre at time = 226.188 ps during transient analysis `tran'.
T9: Vgd has exceeded the oxide breakdown voltage of `vbox' = 1.6 V.
Warning from spectre at time = 233.647 ps during transient analysis `tran'.
T9: The bulk-drain junction current exceeds `imelt'. The results computed
by Virtuoso(R) Spectre(R) are now incorrect because the junction
current model has been linearized.
Warning from spectre at time = 234.588 ps during transient analysis `tran'.
T9: The bulk-drain junction current exceeds `imax'.
Warning from spectre at time = 311.271 ps during transient analysis `tran'.
Convergence difficulties resulted in error requirements being unsatisfied.
T14: The bulk-drain junction current exceeds `imelt'. The results computed
by Virtuoso(R) Spectre(R) are now incorrect because the junction
current model has been linearized.
T14: The bulk-drain junction current exceeds `imax'.
Notice from spectre at time = 311.931 ps during transient analysis `tran'.
T14: The bulk-drain junction leaves the linearized region.
T14: The bulk-drain junction current no longer exceeds `imax'.

Title: Re: cadence error while simulating comparator
Post by ywguo on Apr 2^nd, 2009, 10:18pm

Hi jsun,

I stumble across the same warnings sometimes. Those are just warnings, which do not terminate the transient simulation. I think that are caused by the SPICE model and the spectre algorithm. Don't worry.

Yawei