Stats

  • Locked Locked
  • Replies 4
  • Subscribers 126
  • Views 18373
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Problem with initial conditions for large Capacitor value

palz

Hi,

I am quite new to Cadence spectre. I was trying to simulate a simple RC circuit (with time constant 0.05 s ) with sinusoidal input supply with frequency of 250 Hz.

I have a problem with the initial conditions in the capacitor. The initial condition seems to be ignored when the capacitor value is greater than 1 mF.
What could be the problem?  Kindly help me find a solution to this issue.

Parents
  • palz

    Hi Andrew,

    Thanks a lot. 

    I use spectre  version 11.1.0 64bit, sub-version  11.1.0.341.isr6.

    I would like to clearly explain the scenario of my problem.

    With Time constant, RC = 0.05 s.

    This is my circuit:

    CASE 1A  :

    R10 (in out) resistor r=50K
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1u

     

    CASE 1B  :

    R10 (in out) resistor r=50K
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1u ic=10m

    Comments : Initial condition satisfied

    CASE 2A:

    R10 (in out) resistor r=50
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1m

    CASE 2B:

    R10 (in out) resistor r=50
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1m ic=10m

    Comments : Initial condition satisfied

     

    CASE 3A:

    R10 (in out) resistor r=5
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=10m

     

    CASE 3B:

    R10 (in out) resistor r=5
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=10m ic=10m

     

    Comments : Initial condition not satisfied

    CASE 4A:

    R10 (in out) resistor r=50m
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1

    CASE 4B:

    R10 (in out) resistor r=50m
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1 ic=10m


    Comments : Initial condition not satisfied.

     

     

    So, if you observe all the cases, it is seen that cases 3 and 4 do not correspond to the initial conditions setting. I wonder why that happens in Spectre. I would really appreciate if this is clarified.

    Thanks in advance.

    Regards,
    Pallavi

Reply
  • palz

    Hi Andrew,

    Thanks a lot. 

    I use spectre  version 11.1.0 64bit, sub-version  11.1.0.341.isr6.

    I would like to clearly explain the scenario of my problem.

    With Time constant, RC = 0.05 s.

    This is my circuit:

    CASE 1A  :

    R10 (in out) resistor r=50K
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1u

     

    CASE 1B  :

    R10 (in out) resistor r=50K
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1u ic=10m

    Comments : Initial condition satisfied

    CASE 2A:

    R10 (in out) resistor r=50
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1m

    CASE 2B:

    R10 (in out) resistor r=50
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1m ic=10m

    Comments : Initial condition satisfied

     

    CASE 3A:

    R10 (in out) resistor r=5
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=10m

     

    CASE 3B:

    R10 (in out) resistor r=5
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=10m ic=10m

     

    Comments : Initial condition not satisfied

    CASE 4A:

    R10 (in out) resistor r=50m
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1

    CASE 4B:

    R10 (in out) resistor r=50m
    V0 (in 0) vsource type=sine ampl=1 freq=250
    V11 (net04 net05) vsource type=sine ampl=1 freq=250
    C0 (out 0) capacitor c=1 ic=10m


    Comments : Initial condition not satisfied.

     

     

    So, if you observe all the cases, it is seen that cases 3 and 4 do not correspond to the initial conditions setting. I wonder why that happens in Spectre. I would really appreciate if this is clarified.

    Thanks in advance.

    Regards,
    Pallavi

Children
No Data

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.