determining max frequency of a inverter chain

[daciccad]

Hi,
I have an inverter chain with 10 inverter in HSPICE format. I would to decide what's the max frequency that it can operate. Currently, I the tphl (delay of high to low) and tplh (delay of low to high), and calculate the tp=(tphl + tplh)/2. I would like to know if this is the correct way. Are there other better way to decide?

Thanks a lot.

 

[shravan87]

That sounds correct.

But I'm confused as to what you want to find out. If you want to find the maximum frequency that can be achieved in this technology, why not just make a ring oscillator? Make a chain of odd number of inverters, with the last one connected back as input to the first one. Give an initial condition on any net, and then just see the frequency at which the circuit oscillates.

If you just want to find max freq of your circuit, then keep on increasing input frequency till output fails. You can do this using .alter, sweep and other commands.