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Layout help

Mohana
 Hi,

I am working on LC-VCO. the testbench for the schematic works fine but when i try the testbench for my layout it gives me error with the initial condition. The config mode works for c-only extraction. but when consider the complete paracitics, the transient analysis is stopped because of the error with the initial condition. i have attached a copy of my spectre.out file so reference.

Please help me with this problem.


Notice from spectre during topology check.
    No DC path from node `I7.avS22' to ground, Gmin installed to provide path.


Circuit inventory:
              nodes 237
            bsim3v3 20   
          capacitor 231  
              diode 4    
           inductor 61   
    mutual_inductor 416  
           resistor 232  
            vsource 2    

Time for parsing: CPU = 92.985 ms, elapsed = 135.311 ms.
Time accumulated: CPU = 92.985 ms, elapsed = 135.311 ms.
Peak resident memory used = 26.3 Mbytes.

Entering remote command mode using MPSC service (spectre, ipi, v0.0, spectre1_12141_1, ).

***********************************************
Transient Analysis `tran': time = (0 s -> 1 us)
***********************************************

Warning from spectre during IC analysis, during transient analysis `tran'.
    WARNING (SPECTRE-16255): Initial condition of 1 mV between nodes voutn and 0 converted into initial guess (nodeset) because there is no capacitive path to ground.
Warning from spectre during IC analysis, during transient analysis `tran'.
    WARNING (CMI-2743): I7.C0.d1: Junction current density(I/Area) exceeds `imelt'.  The results computed by Virtuoso(R) Spectre(R) are now incorrect because the junction current model has been linearized.
    WARNING (CMI-2743): I7.C1.d1: Junction current density(I/Area) exceeds `imelt'.  The results computed by Virtuoso(R) Spectre(R) are now incorrect because the junction current model has been linearized.

Important parameter values:
    start = 0 s
    outputstart = 0 s
    stop = 1 us
    step = 1 ns
    maxstep = 20 ns
    ic = all
    skipdc = no
    reltol = 1e-03
    abstol(V) = 1 uV
    abstol(I) = 1 pA
    temp = 27 C
    tnom = 27 C
    tempeffects = all
    errpreset = moderate
    method = traponly
    lteratio = 3.5
    relref = sigglobal
    cmin = 0 F
    gmin = 1 pS


Warning from spectre at time = 1 ns during transient analysis `tran'.
    WARNING (CMI-2743): I7.C0.d1: Junction current density(I/Area) exceeds `imelt'.  The results computed by Virtuoso(R) Spectre(R) are now incorrect because the junction current model has been linearized.
    WARNING (CMI-2743): I7.C1.d1: Junction current density(I/Area) exceeds `imelt'.  The results computed by Virtuoso(R) Spectre(R) are now incorrect because the junction current model has been linearized.

    tran: time = 31 ns        (3.1 %), step = 16 ns         (1.6 %)
    tran: time = 91 ns        (9.1 %), step = 20 ns           (2 %)
    tran: time = 131 ns      (13.1 %), step = 20 ns           (2 %)
    tran: time = 191 ns      (19.1 %), step = 20 ns           (2 %)
    tran: time = 231 ns      (23.1 %), step = 20 ns           (2 %)
    tran: time = 291 ns      (29.1 %), step = 20 ns           (2 %)
    tran: time = 331 ns      (33.1 %), step = 20 ns           (2 %)
    tran: time = 391 ns      (39.1 %), step = 20 ns           (2 %)
    tran: time = 431 ns      (43.1 %), step = 20 ns           (2 %)
    tran: time = 491 ns      (49.1 %), step = 20 ns           (2 %)
    tran: time = 531 ns      (53.1 %), step = 20 ns           (2 %)
    tran: time = 591 ns      (59.1 %), step = 20 ns           (2 %)
    tran: time = 631 ns      (63.1 %), step = 20 ns           (2 %)
    tran: time = 691 ns      (69.1 %), step = 20 ns           (2 %)
    tran: time = 731 ns      (73.1 %), step = 20 ns           (2 %)
    tran: time = 791 ns      (79.1 %), step = 20 ns           (2 %)
    tran: time = 831 ns      (83.1 %), step = 20 ns           (2 %)
    tran: time = 891 ns      (89.1 %), step = 20 ns           (2 %)
    tran: time = 931 ns      (93.1 %), step = 20 ns           (2 %)
    tran: time = 985.5 ns    (98.6 %), step = 14.5 ns      (1.45 %)
Number of accepted tran steps =             54
Initial condition solution time: CPU = 1.999 ms, elapsed = 2.04682 ms.
Intrinsic tran analysis time:    CPU = 20.997 ms, elapsed = 20.75 ms.
Total time required for tran analysis `tran': CPU = 24.996 ms, elapsed = 29.9191 ms.
Time accumulated: CPU = 119.981 ms, elapsed = 1.02863 s.
Peak resident memory used = 31.3 Mbytes.

finalTimeOP: writing operating point information to rawfile.
modelParameter: writing model parameter values to rawfile.
element: writing instance parameter values to rawfile.
outputParameter: writing output parameter values to rawfile.
designParamVals: writing netlist parameters to rawfile.
primitives: writing primitives to rawfile.
subckts: writing subcircuits to rawfile.

 

 

Thanks

Asha
Parents

  • Mohana,

    I just checked it with an example that I used, and it allowed me to set an ic on a purely resistive node, and it worked. That said, I'm a bit suspicious if the node you are setting doesn't have a capacitive path to ground, I'd be surprised if it was really going to have an influence on the initial conditions of the oscillator.

    To access Cadence Online Support you need to register. 

    You  may have to contact customer support - either directly, or via your support channel if you're at a University - with details on what isn't working and with a testcase that shows the problem. Perhaps there's something wrong with the parasitic extraction?

    Or you need to apply your initial conditions to a different node - hard to tell without seeing the data.

    Regards,

    Andrew.

Reply

  • Mohana,

    I just checked it with an example that I used, and it allowed me to set an ic on a purely resistive node, and it worked. That said, I'm a bit suspicious if the node you are setting doesn't have a capacitive path to ground, I'd be surprised if it was really going to have an influence on the initial conditions of the oscillator.

    To access Cadence Online Support you need to register. 

    You  may have to contact customer support - either directly, or via your support channel if you're at a University - with details on what isn't working and with a testcase that shows the problem. Perhaps there's something wrong with the parasitic extraction?

    Or you need to apply your initial conditions to a different node - hard to tell without seeing the data.

    Regards,

    Andrew.

Children
No Data

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