layout extracted netlist simulations for a differential swit

Hello,
I have a switched cap 4th order low pass filter which is differential in nature.
I can do transient/pss/pxf simulations without any problem on a netlist generated from a schematic.
However, I do not see any meaningful outputs when I try to simulate the same circuit using layout extracted parasitics (R+C).

The # of nodes is 31174, # of bsim3v3 is 2881, bourse_1 is 755, capacitors is 50100, resistors are 40022.
With this size netlist, the transients and the pss simulations do not start properly. The opamp outputs hit the rails, the moment the clocks start.

I read spectre.ic from readic menu, I use +parasitics and +csfe to minimize the # of parasitics.

Any help will be greatly appreciated

thanks
analog2000

 

[Andrew Beckett]

On 12/30/12 21:07, analog2000@mailcity.com wrote:

Hello,
I have a switched cap 4th order low pass filter which is differential in nature.
I can do transient/pss/pxf simulations without any problem on a netlist generated from a schematic.
However, I do not see any meaningful outputs when I try to simulate the same circuit using layout extracted parasitics (R+C).

The # of nodes is 31174, # of bsim3v3 is 2881, bourse_1 is 755, capacitors is 50100, resistors are 40022.
With this size netlist, the transients and the pss simulations do not start properly. The opamp outputs hit the rails, the moment the clocks start.

I read spectre.ic from readic menu, I use +parasitics and +csfe to minimize the # of parasitics.

Any help will be greatly appreciated

thanks
analog2000

I can't see any good explanation for this (without seeing the circuit).

+csfe doesn't minimize the number of parasitics (and you shouldn't need
to use that if you're using spectre from any MMSIM release, which you
must be if you're using +parasitics).

I suggest you contact Cadence customer support at
http://support.cadence.com - or via your normal support channel (e.g.
Europractice if a European University).

Regards,

Andrew.