Run transient with cmin option but applied to certain sub-circuits only?

Dear StephanWeber,

I do not know of a means within the Cadence framework to select the portions of a netlist where a convergence capacitance of value cmin should be added to each net. However, a possible workaround is to write a simple script to add a capacitance value of -cmin at each node of those subcircuits you do not wish to have an added capacitance of cmin added. In this fashion, the value of cmin will be added to all circuit nodes, but for those nodes you added the new nodal capacitance of -cmin, the net added capacitance wll be zero.

Shawn

Stephan,

You can do this via the MTS interface these days - assuming that you're using a config for your test, go over the test name in Assembler, and Right Mouse→MTS Options. You'll see there that you can set cmin on specific cells or specific instances. That's the cleanest way in ADE, but it's also possible as a option statement (can be done via the additional arguments on the Simulation→Options→Analog form too (on the Miscellaneous tab) - see How to add cmin to specific instances or subcircuits during Spectre simulation?

Andrew

I should also point out that cmin should really be a last resort - it normally suggests a problem with your device models.

Andrew

Thanks for these hints! In my case the design was really very sensitive to parasitic caps, so post-layout simulation was giving unfortunately also a significant performance change. No problems on device models so far.

Bye Stephan