Hi all,

is there a method to calculate running averages in Verilog-AMS? I would need to measure the running average of a voltage with a time window of TS second. So that the expression in pseudo-math language would be:

avg = 1 /TS * integral_from($asbtime-TS)_to($abstime) vin(x)dx

where $abstime is the running time.
As model output I would need a time continuous function: avg(t).
I am not sure if the VerilogAMS function "idt" is suitable.

Any ideas?

Many thanks,
Cristiano

In case you are not able to see the answer at the Cadence support site, the answer to your question is: yes, idt is applicable, but you also need to factor in the time window. You can rewrite the integral to the following form:

avg = 1 /TS * integral_from($abstime-TS)_to($abstime) vin(x)dx

avg = 1 /TS * (integral_from(0)_to($abstime) vin(x)dx -
                     integral_from(0)_to($abstime-TS) vin(x)dx)

avg = 1 /TS * (integral_from(0)_to($abstime) vin(x)dx -
                     integral_from(TS)_to($abstime) vin(x-TS)dx)

avg = 1 /TS * (integral_from(0)_to($abstime) vin(x)dx -
                     integral_from(0)_to($abstime) vin(x-TS)dx)

avg = 1 /TS * integral_from(0)_to($abstime) (vin(x) - vin(x - TS))dx

Now you can use idt() and a delay operator to implement this transformed operation.

Marq

Hi again,

I just googled this thread with a skill code by Andrew:

http://groups.google.com/group/comp.cad.cadence/browse_thread/thread/bc276d85b43...

I also tried the VerilogAMS code suggested by Marq and they seems quite similar. Actually there is a small discrepancy between the results of the two methods but in my case this may be probably accepted.

Thanks,
Cristiano