HSPICE power calculation help: AVG power vs Integrated Power

[moharaza]

Hi,

I am having a problem with power calculation in HSPICE.

1. I calculated power with AVG power command.
2. I integrated current over the period and multiplied with vdd, then divided the energy with period to get the power.

surprisingly those power numbers are different. over a 500 cycles, I am seeing at some instances the difference is as much as 2 orders of magnitude. Can anyone give me any explanation as to why this is happening.

sampling time is 30ps, cycle time 100ps. How does hspice calculate AVG power, or how does it do integration if sampling time is 30ps.

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Thanks

 

[ebuddy]

Does your circuit have any inductors?

Another suggestion, try your 2 methods on a very simple circuit, and get the matching number first.

 

[moharaza]

no, it does not have inductors.

I tried with sample circuit, on that test circuit the figures were close.

But, for a full adder it is very different.