How complex is it ? And the best way to do it using ADS or Ltspice.

 

Easy - just buy the ICM7555 instead. Or the TLC555.

 

Easy - just buy the ICM7555 instead. Or the TLC555.

But I need the cmos schematic- mosfet level simulated

 

There is a TLC555 model in @Bordodynov 's SPICE models which you can download for free.

 

There is a TLC555 model in @Bordodynov 's SPICE models which you can download for free.

Hey, can you post the link of the TLC555 model?

 

Google "TLC555 SPICE model".

That will almost certainly give you a link to TI's website where you can download their model files. If not, go to TI's website and search for it there.