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Modeling >> Behavioral Models >> VerilogA apply transient final conditions to AC/noise analysis
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Message started by anamania on Jun 20^th, 2013, 7:49am

Title: VerilogA apply transient final conditions to AC/noise analysis
Post by anamania on Jun 20^th, 2013, 7:49am

Hi,
I have built a VerilogA module that is the AGC for an analog PGA. At the end of transient analysis, the module sets the gain of the PGA so that the output swing settles to a target value whatever the input swing is. How do I apply this gain, says 5 bit control, to subsequent AC & noise analysis? I want to complete all analysis in one simulation.

Thanks.

Title: Re: VerilogA apply transient final conditions to AC/noise analysis
Post by Ken Kundert on Jun 21^st, 2013, 6:24am

Try setting restart=no on the AC analysis, and make sure it is run after the transient analysis.

-Ken

Title: Re: VerilogA apply transient final conditions to AC/noise analysis
Post by weber8722 on Mar 1^st, 2015, 11:06am

Hi Ken,

can you give a short example spectre netlist.
I think this question is often asked.

In Cadence I typically solve the problem with ADEXL and calcVal, but a pure spectre solution would be much more elegant!

Bye Stephan

Title: Re: VerilogA apply transient final conditions to AC/noise analysis
Post by Ken Kundert on Mar 1^st, 2015, 12:01pm

Code:

// Test case where the AC analysis that follows a transient uses the operating
// point from the final point of the transient analysis.

simulator lang=spectre

Vin (in 0) vsource type=pulse val0=0 val1=1 mag=1
R (in d) resistor r=1k
D (d 0) dmod
model dmod diode

ACpre ac start=1 stop=1M
TR tran stop=1u
ACpost ac start=1 stop=1M prevoppoint=yes