Parasitics Used for IR Drop

[rixmaestro]

Hello,

I am just wondering which resistance/capacitance values are being used to do the IR drop analysis?

From what I understand, there are at least three possible sources of the RC values:

• set_layer_rc commands
• LEF file of the technology
• extract_parasitics using an external models/rules

Based on some trials I did, it seems that the analyze_power_grid command will only work properly if I do the set_layer_rc commands even if the LEF has some RC values, and the extract_parasitics did its thing. Is there also a way to choose which RC values to use for the analyze_power_grid command?

[maliberty]

@gadfort

[gadfort]

analyze_power_grid will use the values from set_layer_rc first, if these are not set, it will fall back to using the values from LEF.
This command is not able to use the values from an external extraction.

[rixmaestro]

Thanks for the response!

Are there plans in the future to use the values from extract_parasitics?

[maliberty]

Not currently. I don't think it would increase the accuracy much as it is just resistance that matters.

[rixmaestro]

Understood! Thanks!