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Overcoming Blowup of Quantities in NCSIM (Read 4635 times)
badamsssl
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Overcoming Blowup of Quantities in NCSIM
Mar 20th, 2007, 9:57pm
 
HI
could you please help me overcoming the following problem while simulating a Behavioral Charge Controlled model developed in VHDL AMS through an inverter:

Error found by spectre during DC solution estimation, during IC analysis,
       during transient analysis `amsAnalysis'.
   There were 7 attempts to find the DC solution. In 13 of those attempts, a
       signal exceeded the blowup limit of it's quantity. The last signal that
       failed is U(uInv.A1.qIn) = -1.80144 G, for which the quantity is `U'
       and the blowup limit is (1 G). It is possible that the circuit has no
       DC solution. If you really want signals this large, set the `blowup'
       parameter of this quantity to a larger value.

Thanks in Advance
--Srinivas
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Ken Kundert
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Re: Overcoming Blowup of Quantities in NCSIM
Reply #1 - Mar 20th, 2007, 10:59pm
 
The signal on uInv.A1.qIn exceeds 1.8e9, and as a result the simulator thinks something is going wrong. Have you looked to see why the signal on uInv.A1.qIn is greater than 1.8e9?

-Ken
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badamsssl
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Re: Overcoming Blowup of Quantities in NCSIM
Reply #2 - Mar 21st, 2007, 6:12pm
 
HI

Thanks for your reply....But I have fixed the problem....
The mistake I did was to initialize the free quantities (as we usually do in VHDL digital modules or a typical C++ code)  to either 0.0 or 1.0.
so when I have the Gate Capacitences or Charges which would typically be in the range of E-34 or even less, the rise in those quantites when compared to 0.0 or 1.0(which it was initialized to in the model...) exceed the blowup limit of the quanitity (which according Cadence Spectre is around 10E-8 or some value which is leass than that seen in the quantity).....So , It gave an error message and stopped analysing

So Now I removed the initialization of those quantities and the model working pretty well

Any how thanks for having such a wonderful forum for the designers and your book " The Designer's guide to Spectre and Spice" which gives an outline on a typical simulator.....

---Srinivas
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