How to control "isnoisy" property for analogLib's "switch" component?

P.S. Using "Simulation->Options->Analog->Noise contribution" to filter noise contributions seems to work, but it gets messy for a big number of instances. Thus I'd rather control the individual contributions by setting the isnoisy properties.

Hi Jorge,

Follow these steps:

1. Copy the cell switch from analogLib to your own library (using Right Mouse Button -> Copy in the library manager over the cell name)
2. In the CIW, use Tools->CDF->Edit
3. Pick yourLib and switch as the cell, and choose "Base" for the CDF type
4. Add a new row with parameter name "isnoisy", Type "cyclic", and prompt "Generate noise". In the fields at the bottom, set the choices to "yes no" (without quotes) and the default to "yes".
5. Use the arrow icons to move the isnoisy to the place you want in the order of parameters (e.g. at the bottom).
6. Pick the Simulation Information  tab.
7. Change the simulator cyclic to "spectre"
8. Add isnoisy into the instParameters list.
9. OK the form
10. Contact customer support to ask for the analogLib switch component to be enhanced to have this field as standard.

Now you can instantiate your own switch component which has an isnoisy parameter.

Regards,

Andrew.

Thanks so much for the detailed reply, Andrew. I followed the procedure and behaviorally, it works (the relay component is netlisted with the appropriate isnoisy property value); however, it seems I accidentally found a bug in the noise behavior of the relay component (I checked the below results with the analogLib switch component, and the behavior is the same, so I believe it's a bug).

In a nutshell, the relay component fails to update the generated noise as its control voltage changes. In the example below I simulated voltage of a DUT (transient noise simulation) where the control voltage changes halfway the simulation (the "DUT_switched"), and compared with that of "static" DUTs where the control voltage is kept constant throughout the simulation ("DUT_static_Ropen" and "DUT_static_Rclosed"). For reference and further comparison, I also included the noise of two analogLib resistors with the same "Ropen" and "Rclosed" resistances (1kOhm & 10Ohm, respectively). I actually did two simulations, where I just changed the polarity of the clock signal ("CLK") controlling the switched relay.

As can be seen from the waveforms, the noise of the switched relay fails to update properly when the control voltage changes.

It seems this requires further debugging (I could fill a case, but I'll take some time as currently I'm overloaded).

Thanks and regards, Jorge.

(P.S. BTW, the legend entries in the waveform viewer show purple boxes for blue traces... I noticed this when switching to ICADVM 18.1.500.6).

P.S.2: This is the netlist I am using:

// Generated for: spectre
// Generated on: Dec  6 18:18:17 2019
simulator lang=spectre
global 0
parameters CLKGEN__Freq=100M CLKGEN__Trisefall=20p \
    SIM__TRAN__Noise_Fmax=1T SW__Rclosed=10 SW__Ropen=1k VDD=900m VSS=0 \
    CLKGEN__Tperiod=1/CLKGEN__Freq SW__vClosed=0.6*(VDD+VSS) \
    SW__vOpen=0.4*(VDD+VSS) CLKGEN__Tdelay=0.5*CLKGEN__Tperiod \
    CLKGEN__Tguard=0.05*CLKGEN__Tperiod*0 \
    CLKGEN__Twidth=0.5*CLKGEN__Tperiod-CLKGEN__Trisefall \
    SIM__TRAN__Tstop=1.0*CLKGEN__Tperiod \
    SIM__TRAN__Noise_Fmin=1/SIM__TRAN__Tstop

// Library name: jlagos__models__analogLib
// Cell name: jlagos__switch__testbench__cds_testcase
// View name: schematic__analogLib_switch
PHI1__vpulse (CLK 0) vsource type=pulse val0=0 val1=VDD \
        period=CLKGEN__Tperiod delay=CLKGEN__Tdelay rise=CLKGEN__Trisefall \
        fall=CLKGEN__Trisefall width=CLKGEN__Twidth-CLKGEN__Trisefall
W2 (0 DUT_static_Rclosed vdd 0) relay vt1=SW__vOpen vt2=SW__vClosed \
        ropen=SW__Ropen rclosed=SW__Rclosed
W1 (0 DUT_static_Ropen 0 0) relay vt1=SW__vOpen vt2=SW__vClosed \
        ropen=SW__Ropen rclosed=SW__Rclosed
DUT (0 DUT_switched CLK 0) relay vt1=SW__vOpen vt2=SW__vClosed \
        ropen=SW__Ropen rclosed=SW__Rclosed
V0 (vdd 0) vsource dc=VDD type=dc
R2 (0 REF_Ropen) resistor r=SW__Ropen isnoisy=yes
R3 (0 REF_Rclosed) resistor r=SW__Rclosed isnoisy=yes
simulatorOptions options psfversion="1.1.0" reltol=1e-3 vabstol=1e-6 \
    iabstol=1e-12 temp=27 tnom=27 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 noiseon_inst=[ DUT W1 \
    W2 R3 R2]
tran tran stop=SIM__TRAN__Tstop errpreset=conservative \
    noisefmax=SIM__TRAN__Noise_Fmax noisefmin=SIM__TRAN__Noise_Fmin \
    noiseseed=1151 maxstep=1p write="spectre.ic" writefinal="spectre.fc" \
    annotate=status maxiters=5
finalTimeOP 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
save CLK DUT_switched DUT_static_Ropen DUT_static_Rclosed REF_Ropen REF_Rclosed
saveOptions options save=allpub saveahdlvars=all

Jorge,

I think it would have taken you the same amount of effort to log this netlist to support.cadence.com as it did to post it here, and then one of my colleagues could have filed the CCR and have it associated with you as a customer (which would have been better for the likelihood of it being fixed sooner), rather than it being dependent upon me to take care of it.

Anyway, because it bothered me, I found the time today and filed two CCRs:

2196116 Legend color is purple for blue trace
2196115 relay produces incorrect noise after switching with transient noise

Regards,

Andrew.

Thanks so much, Andrew!. Please note the main reason why I sometimes prefer not to file the CCRs myself is because it can potentially take more time to properly follow-up on the case (provide additional info, test cases, further experimenting, etc.); but I'll try to do it myself as time allows! Thanks again for your help!.

Hi Jorge,

A little update on this old thread. Both CCRs are now fixed:

2196116 Legend color is purple for blue trace (fixed in IC6.1.8 ISR13 - available a few months ago)
2196115 relay produces incorrect noise after switching with transient noise (fixed in SPECTRE20.1 ISR4 - scheduled to be released around 5th March 2021)

I tested the first a while ago, and the second I just tested. It now behaves properly in both transient noise and pnoise analyses.

Regards,

Andrew

Hi Jorge,

A little update on this old thread. Both CCRs are now fixed:

2196116 Legend color is purple for blue trace (fixed in IC6.1.8 ISR13 - available a few months ago)
2196115 relay produces incorrect noise after switching with transient noise (fixed in SPECTRE20.1 ISR4 - scheduled to be released around 5th March 2021)

I tested the first a while ago, and the second I just tested. It now behaves properly in both transient noise and pnoise analyses.

Regards,

Andrew

That's good news, Andrew! Thanks for the update and for your following up on this.

Regards,

Jorge.