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kiran123

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What these Spectre Warnings have impact on results
Oct 24^th, 2006, 2:55am

Hi Experts,

I have question while running spectre using MDL i am getting below warnings i understand what these mean but not aware how this impact my simulation accuracy.

****************************LIST of WARNINGS *******************************************
a) I0.M38: Vgd has exceeded the oxide breakdown voltage of `vbox' = 2.27 V.
b) I0.M43: Vgs has exceeded the oxide breakdown voltage of `vbox' = 3.5667 V.
c) I0.M43: Device leaves the gate-source oxide breakdown region.
d) I0.M7: Device leaves the gate-drain oxide breakdown region.
e) I0.M31: The bulk-drain junction current exceeds `imax'.
f) I0.M31: The bulk-drain junction current no longer exceeds `imax'.
****************************LIST of WARNINGS *******************************************

Can you please let me know is there any option to specify to improve the accuracy while maintaining these warnings

thank you
kiran

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ACWWong

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Oxford, UK

Re: What these Spectre Warnings have impact on res
Reply #1 - Oct 24^th, 2006, 3:42am

what i would do would to investigate what is going on in the circuit first, then try things like putting in some supply impedance or similar "lossy" real artifacts to your netlist in an attempt to tame these momentary limit overshoots which arise in warnings....

probably a naughty thing to do would be to increase the limits a bit to see if helps...
try spectre -h param_limits or look it up in the manual....

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bernd

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Munich/Germany

Re: What these Spectre Warnings have impact on res
Reply #2 - Oct 24^th, 2006, 5:16am

imelt (imax) and vbox are bsim3v3 & bsim4 model parameter

Junction diode model parameters:
103 imelt=`imax' A Explosion current.
104 ijth (A) Alias to `imelt'.

Operating region warning control parameters:
222 vbox=1e9*tox V Oxide breakdown voltage.

See also one of my previous postings:
http://www.designers-guide.org/Forum/YaBB.pl?num=1132058634/1#1

Bernd

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Just another lonesome cad guy

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Ken Kundert

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Re: What these Spectre Warnings have impact on res
Reply #3 - Oct 24^th, 2006, 7:29am

The vbox message is just a warning to you that the voltage across the oxide is too high to be maintained without damage given the thickness of the oxide. The actual damage is not modeled, so the simulation results are unaffected by the presence of this message.

The same is true for imax. Imax is a user specified limit on the junction current, that when exceeded produces a warning message but does not change the behavior of the device model. If, however, you go further and exceed imelt, then you have exceeded the limits of the model and the results will be incorrect.

-Ken

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Geoffrey_Coram

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Massachusetts, USA

Re: What these Spectre Warnings have impact on res
Reply #4 - Oct 24^th, 2006, 10:13am

bernd wrote on Oct 24^th, 2006, 5:16am:

imelt (imax) and vbox are bsim3v3 & bsim4 model parameter

Per the Compact Model Council's evolving policy on standard models, these are *not* official BSIM3/4 model parameters; they are extra parameters in Cadence's implementation of these models (as well as, I presume, other MOS models).

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If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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