How to make a block Noise-less while doing Noise analysis in Spectre

Better still, use Simulation->Options->Analog and then on the Main tab, at the bottom there is a NOISE OPTIONS section. You can decide to selectively turn on or off the noise contributions from blocks - there's a list of instances and a Select button to pick the instances.

If using a really old version, you can achieve the same by using the Additional arguments field on the Miscellaneous tab, and entering noise_off=[I1 I2.I3] etc. The names have to be "netlist" names though. Much easier if you can use the UI by using a recent enough IC version.

This works by internally in the simulator utilizing the isnoisy parameter of the devices (almost all devices support this now) but without you having to modify your schematics or requiring the CDF for the devices to netlist the isnoisy parameter. Note that for this to work for Verilog-A models which have noise contributions, they must implement an isnoisy instance parameter.

Regards,

Andrew.

Dear Andrew,

Thanks for the reply.

Dear Andrew,

I don't know whether it is actually doing for a instance in down the hierarchy.

I tried /I1/I2/I101.

Whether it would work ? Please comment on this

Kind Regards,

Frank - the name only has to be a netlist name if you use the noiseoff_inst or noiseon_inst in the Additional arguments field. If you use the specific field on the form (or use the "Select" button), then it should be the schematic name (i.e. /I1/I2/I3) and that will be mapped to the netlist name during netlisting.

RFStuff - yes, this should work. If you look at the noise summary table in the results, you should see no noise contribution from any device in that block.

Andrew.

is it possible that it acts on cells and not per instance? i have a cell that is instantiated multiple times and i get the same results regardless which instance i select to turn off noise

Dear Noam F,

Noam F said:

is it possible that it acts on cells and not per instance? i have a cell that is instantiated multiple times and i get the same results regardless which instance i select to turn off noise

Please refer to the Cadence On-line Support URL:

https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od0000000vK9ZEAU&pageName=ArticleContent

However, you are referencing a 7 year Community post which - in addition to not consistent with Mr. Andrew Beckett's Forum post guidelines -  may not refer to the version of Cadence tools you may be referencing. You did not indicate what version of the tools you are using (also not recommended in the guidelines), so I can't provide any more specific information. However, the URL I provided does suggest the arguments to the noise on/noise off contribution netlist entry line is on a per instance of a subcircuit and not on all instances of the subcircuit unless you explicitly enter all of the instance names.

I hope this is addressing your question and I understood it correctly Noam F.!

Shawn