# How can I calculate dynamic power for an SRAM with Hspice?

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#### reza1978

##### Newbie level 5
Hi all,

I designed an 32kb SRAM with its decoder, sense amplifier and .... and wrote its netlist with Hspice Now I want to calculate its dynamic power. I have some problems:

1- How should I calculate its dynamic power when the inputs are pulse?

2- Maybe one way is that I calculate the total capacitances in each node and use this formul: P=C×f×Vdd² but the problem is that when I use for example:
.PRINT CGG=LX18(OUT)
there isn´t any result in .LIS file or in .MT0 file,

so I can´t understand how I should calculate the capacitances in the transient mode.

3- When I put .OP in the netlist I saw total capacitances for all transistors but the problem is that they are for DC mode. Can I use these results for transient mode?

Reza

Just run a reasonable number of cycles with reasonable
address / data activity, get to a charge-per-cycle value
from the supply current integrated over the run and the
number of cycles, and then you can interpolate / extrapolate
to whatever frequency.

Because many MOSFET capacitances vary w/ operating
point, you really want to get results from a full switching
analysis.

Hi, It means that I should calculate total Q for each node and then caiculat ethe dynamic power?

I'd just look at the current in your VDD supply (or supplies
if you have a mixed core / I/O scheme). Summing up all
of the individual nodes is doing it the hard way (and the
current in VDD, averaged, is already giving you the rollup).

Re: How can I calculate dynamic power for an SRAM with Hspic

hi frnd can i see ur schematic den i only i will be able to help.

Re: How can I calculate dynamic power for an SRAM with Hspic

hi dere reza1978, can i see ur SRAM schemtic, i can help u

hi dere reza1978, can i see ur schematic, i can help u.

• malaee

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