Hspice Convergency Issue

[Willt]

Dear friends,

I am now studying convergency issue in Hspice.
As all of you know, convergence is defined as the ability to obtain a solution
from a set of circuit equations within a given tolerance criteria.

Could anyone explain the above mentioned definition using a simple example?
Your help is highly appreciated!
Thank you

Will

P.S. I would love to click "help me" for your good explanation.

 

[hr_rezaee]

Hi
read any numerical computing books.

see known algorithms such as Newton-Raphson or Gause-Seidel for better realization.
Methodhttp://www.shodor.org/UNChem/math/newton/index.html

regards

 

[yjkwon57]

Hi!
The non-linear characteristics of some components will lead to the convergency problems. If you want to get a solution in a shorter time, you will use the component model showing a smooth gradients.

Added after 6 minutes:

One more thing to say is the circuit matrix is to be pivoted so as to reduce the fluctuation.

 

[shaikhsarfraz]

Most of the tolls use iterative methods such as newton raphson method to arrive at solution.

For Newton Raphson methods to converge it requires to meet certain conditions.

Most of the convergence problems are seen for dc and transient analysis

regards
Sarfraz

 

[rmy_babu]

Hi
read any numerical computing books.

see known algorithms such as Newton-Raphson or Gause-Seidel for better realization.
Methodhttp://www.shodor.org/UNChem/math/newton/index.html

regards

 

[smith123]

read numerical computing book by
gerald wheatley it is extremly amazing Book.

 

[rush3k]

i agree with the people who say you should study some numerical methods concerning this ... newton raphson methods, traipezoidal methods are probably the ones mostly used in simulators. read about their deficiencies.

a simple example will be that you use a numerical method eg simpson's 1/3 rule to solve an integration problem, you can get the error to be 5% from the real value (that's when you solve the integration completely without numerical methods). if you use a more accurate method like the traipezoidal rule, your error will reduce to maybe 1% from the actual number. so while simpson's rule might be faster, it might not necessarily be more accurate. it all depends on how accurate you want the result.

 

[rfzheng]

normally,hspice Convergency problem has close relatoinship with
the time step ,because numerical computing is commonly need reasonable step.

if there is breakup in the circuit , or short of some parameters of the device, it will also meet convergence issue.

 

[wmbasslake]

initial value is another factor

 

[gamma1]

Some device model have issues too

 

[djones1]

some netlist create convergency isuue