Memory instance : ULTRASIM simulator setting

Hello,

I would like to know what are the simulator settings you use for a "memory instance" typ simulation (transient simu of ~5ns), with just the checking of an output bit, for the sensing operation.

My memory instance is a the smallest instance in terms of bitcells. It means it's "far" below than 1M bits.

Of course there is a "MUX strategy" inside the memory instance, and for the sensing, there is a "sense amplifier + comparator", plus a "biasgen and a clkgen" blocks, and I would say all these three must be simulated at analog point of view.

The simu results, I am checking, are more or less :

-output bit of the comparator

-2 inputs of the sense amplifier (one input coming from the ref and the other from the sensed bitcell)

-clk signals

I am using the following settings :

-ULTRASIM (Cadence) :

usim_opt speed=6

usim_opt sim_mode=a inst= sense_amplifier_block or I can put the three blocks (SA, clkgen, bisagen) as analog. The simu results are almost the same.

with ULTRASIM : in full-analog mode :

 usim_opt speed=6

usim_opt sim_mode=a

it takes almost a day and I have very different results. 

My issue, is that I have different results according ot the simulator settings, and I am not sure of which ones are golden.

thanks a lot or any help !!

P.