Why DC analysis doesn't converge

[Allen]

Can anyone give me some advice on my dc analysis? I am designing a
digital PLL, when I run dc analysis for the charge pump circuit,
cadence tells me that error is found because the step size is too
large and it doesn't converge.

Thanks.
Best,
Allen

 

[salim j athfal]

On Dec 3, 6:06 am, Allen <ocean...@yahoo.com> wrote:

Can anyone give me some advice on my dc analysis? I am designing a
digital PLL, when I run dc analysis for the charge pump circuit,
cadence tells me that error is found because the step size is too
large and it doesn't converge.

Thanks.
Best,
Allen

Normally convergence problems for step size comes for transient
analysis. Try to find out the exact point of non convergence from the
output log file and read the your simulator ( specter /hspice) manual
to fix the nonconvegence. This can done by changing some of the
simulator options(band aid soultion) or putting some impedence at
exact point of non-covergence.
please refer http://www.ecircuitcenter.com/SpiceTopics/Non-Linear%20Analysis/Non-Linear%20Analysis.htm.