CALCULATING internal power

[subbu512]

How do we calculate internal power from .lib? .lib contains the attribute of Internal power, internal power is mentioned in the matrix form for every pin?
How to come up with a value for a particular cell?

 

[englishdogg]

@subbu512

By default, the internal cell power is derived from the power tables in the library. I am not sure if the syntax can vary as per technology node but below is as per my understanding.

As you mention there is a table for every cell and it will have say index_1 and index_2 as well which are defined in the beginning.Therefore index_1 will fit the row and index_2 will make it to the column side of that table.
To what value index_1 and index_2 fit and coincide in that table will be the final cell_internal_power.

 

[pd_789]

Hello

I am finding negative rise power numbers in .lib file of TSMC and negative internal power in power reports of PowerCompiler... What does these negative power numbers mean.

Thanks in advance

 

[englishdogg]

this has to be some computation issue for sure. Time to call the support team of Power compiler

 

[Prashanthanilm]

How do we calculate internal power from .lib?

Output pin will have internal power with respect to related pin .
Eg : Q with CLRZ/PREZ
Here you will have the table for LOAD and Transition slew values.
You can get the internal power for the respective load and slew.

.lib contains the attribute of Internal power, internal power is mentioned in the matrix form for every pin?

Yes, Input pin will have internal power [depends on input slew].
Output pin will have internal power on related pin[depends on slew and load ].

How to come up with a value for a particular cell?

You will get the load value from load spec and slew from experiments.
Tool will use the above as input and calculate the power

More Information :
Internal Power :
Internal power is the power dissipated within the boundary of a cell.
During switching, a circuit dissipates internal power by the charging and discharging of any existing capacitance internal to the cell.
Internal power includes power dissipated by a momentary short circuit between the P and N MOS called short circuit power.

Switching Power:
The switching power of a driving cell is the power dissipated by the charging and discharging of the load capacitance at the output of the cell.

The total load cap is the sum of output net and gate cap on the driving output