The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> Timing Simulators >> How to make VCO start to oscillate in ultrasim?
https://designers-guide.org/forum/YaBB.pl?num=1325825830

Message started by ahhfyz on Jan 5^th, 2012, 8:57pm

Title: How to make VCO start to oscillate in ultrasim?
Post by ahhfyz on Jan 5^th, 2012, 8:57pm

Hi, everyone!

I am a beginner in ultrasim. Now I try to simulate a vco in ultrasim. sim_mode is set to "a(analog)", and speed is "1", but it cannot start to oscillate.

I guess it is a tolerence problem, but don't know how to further set tol.

Regards!
Yang

Title: Re: How to make VCO start to oscillate in ultrasim?
Post by raja.cedt on Jan 6^th, 2012, 2:06am

you have to use initial condition in ultrasim as well

Title: Re: How to make VCO start to oscillate in ultrasim?
Post by weber8722 on Jan 10^th, 2012, 5:50am

Hi, I would add a little vpwl or ipwl source to kick-start the oscillator. This should work independent to any simulator (hspice, spectre, ultrasim, ams-designer,...).

Bye Stephan

Title: Re: How to make VCO start to oscillate in ultrasim?
Post by raja.cedt on Jan 12^th, 2012, 10:07am

hello Stephan,
i guess in altrasim you don't have pulse input i guess.

Thanks,
Raj.

Title: Re: How to make VCO start to oscillate in ultrasim?
Post by ahhfyz on Jan 12^th, 2012, 10:39pm

weber8722 wrote on Jan 10^th, 2012, 5:50am:

Hi, I would add a little vpwl or ipwl source to kick-start the oscillator. This should work independent to any simulator (hspice, spectre, ultrasim, ams-designer,...).

Bye Stephan

Setting "initial condition" can kick-start the oscillator, but ipwl fails.