Question on Operating condition

[vcnvcc]

While going through ASIC Chip Synthesis by Himanshu Bhatnagar, (page=67) this question popped up on operating condition

It is written as -- A library is characterized using one set of operating conditions. During synthesis or timing analysis, if another set of operating conditions is specified, then DC uses the K-factors to derate the delay values based upon the specified operating conditions.

Now my question is - if library guy characterized a lib at particular PVT, then in that case while using that lib in DC do I have to use same PVT/operating condition by while that lib is characterized?

If I wanted to use another corner then dose it mean K-factor will come in to picture?

(I searched on net for the same, but i am getting confused.) Can you please put some light on it? and share your insights?

**broken link removed**

 

[DFT_designer]

Hi,

I think that the summary of the question is: Synthesis is done using which PVT lib ?
My answer to this question is, the lib should worst case: P=SS (slow slow), V=minimum voltage, T=Maximum temperature (this can change in recent technology nodes)
To answer why using this lib ? Because, in synthesis we need to have a clear setup timing (worst case affect setup time and best case affect hold time)
So after performin synthesis we need to have no timing violations in setup time, because they cannot be fixed in place & route. Hold time cane be fixed by P&R tool by adding buffers.
In P&R all libs are used.

Does this answer the question ?
Regards

 

[vcnvcc]

Thanks for replying, I agree with you statement... however this doesn't answer my question.

I wanted to know when DC uses K-factor? It uses when I use another operating cond other than one on which lib is characterized?
Actually not able to pickup what book is saying you know..

 

[Kaustav]

Hi Vcnvcc,
This K-factor or derating factor what ever you call can be applied in any PVT corners.

If you want to derate ur design by 20% [so your k=1.2] means all your data or clock is coming late by 20%
Previously, say any data that was coning after time T, now due to derate it will come at time 1.2T. means what ever the delay value, it will be straight-forwardly multiplied by 1.2

SDC Command to set this derate:
set_timing_derate -late 1.2

Derating factor's value less than 1 means data comes faster than normal
SDC Command:
set_timing_derate -early 0.8

in this case data comes at time 0.8T [20% faster than previous]