``` WARNING Current core area is too small for a power grid

Question

``` WARNING Current core area is too small for a power grid WARNING THE POWER GRID WILL BE MINIMIZED ```

manili · Answer

AFAIK this usually should not cause bad things happen But it will change the size of the V H PDN pitch so this may cause your FP PL depending on settings you choose So as a result please check the LVS results to make sure that everything s OK P S This is based on my knowledge maybe someone else could help much better

Krzysztof Herman · Answer

< U02BL33QJE5> Hi the problem is when You use this small design as a macro because it distributes vertical power straps using other pitch and offset so there is no chance to make it aligned with the top level of the macro

manili · Answer

< U01GLU3UDRD> That s exactly correct However you can change the size of the wrapper macro straps

Krzysztof Herman · Answer

yes I was thinking about that but i think it can bring me some more problems trying to align it with caravel

Krzysztof Herman · Answer

moreover the deadline is close

Krzysztof Herman · Answer

what I did was to merge 2 macros in 1 thus I do not have this warning and PDN straps are spaced using default values

Krzysztof Herman · Answer

BTW do You know what those parameters FP PDN VOFFSET FP PDN VPITCH FP PDN HOFFSET FP PDN HPITCH exactly mean They have values assigned but the values do not match the physical distances when measured y the final GDS usin Klayout and a ruler

manili · Answer

< U01GLU3UDRD> You can check it but for example FP PDN VPITCH The distance from the middle of two vertical straps with THE SAME name e g two vccd1 For more info plz check

Krzysztof Herman · Answer

ok I have measured it and it perfectly make sense for the vertical straps

Krzysztof Herman · Answer

what about the horizontal rails

manili · Answer

< U01GLU3UDRD> FP PDN HPITCH Exactly the same rule as the vertical

Krzysztof Herman · Answer

but it does not match to be like 153 u

manili · Answer

it should be around 180u AFAIK

Krzysztof Herman · Answer

set env FP PDN VOFFSET 16 32 set env FP PDN VPITCH 153 6 set env FP PDN HOFFSET 16 65 set env FP PDN HPITCH 153 18

Krzysztof Herman · Answer

so first booth H and V have the same offset and pitch

Krzysztof Herman · Answer

however the horizontal grid seems to be much more dense

Krzysztof Herman · Answer

Krzysztof Herman · Answer

the outside macro does have 153 6 of pitch but the horizontal lines are much more closer

manili · Answer

That s funny Why ur met5 is vertical and met4 is horizontal

Krzysztof Herman · Answer

who knows

manili · Answer

Did you change ur settings

Krzysztof Herman · Answer

no

manili · Answer

Well looks like you need an expert to help smile

manili · Answer

Would you mind share ur config file here

Krzysztof Herman · Answer

I agree

Krzysztof Herman · Answer

of course

Krzysztof Herman · Answer

config tcl

manili · Answer

what about the wrapper

Krzysztof Herman · Answer

the result of this flow will be used as a macro instantiated by the wrapper

Krzysztof Herman · Answer

so I have like 2 levels of macros

manili · Answer

I know I mean would you mind share the config file of the wrapper as well

manili · Answer

I see some strange options in ur config

Krzysztof Herman · Answer

Until now I have not used wrapper I plan to use the default one of the caravel

manili · Answer

OK got it Do you want to see my github repo Maybe it can help you

Krzysztof Herman · Answer

if You be so kind would be nice

manili · Answer

manili · Answer

Plz check these files

manili · Answer

It s midnight here and I got to go Plz feel free to ask any questions regarding my settings I d be so much happy to help

Krzysztof Herman · Answer

as I can see You do not care much about the macr position

Krzysztof Herman · Answer

mprj 1000 1500 N mem 1000 200 N

Krzysztof Herman · Answer

what about Your DRC is it ok

manili · Answer

Zero DRC errors

Krzysztof Herman · Answer

interesting

Krzysztof Herman · Answer

in fact now I am changing my design to have only one macro level as You have

Krzysztof Herman · Answer

so hope it will work

manili · Answer

Plz note that the best idea is to instantiate all macros in the wrapper Not the user design

manili · Answer

Take a look at this design It has a loooot of macros all in the wrapper <https github com VLSIDA openram testchip>

manili · Answer

Only put your digital design which needs to be synthesized in the user design and then instantiate it as a macro in the wrapper I did try what you re about to do and it was a whole failure for me

Krzysztof Herman · Answer

ok taknks for Your support