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Subject: LVS Matching error
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isazul
Posts: 26
Online: User is Offline
3/05/2008 8:56 AM  
Hi everybody
I'm using Diva from Cadence to run LVS.
I get many nets and devices mismatch when running an LVS. This is due to M factor of mos transistor, and also because I draw my MOS transistors in Layout using multifingered design. I thought LVS didn't recognize parallel device, but
I checked DivaLVS.rul file and parallel simplification seems to be set by permuteDevice statement. (permuteDevice parallel "nfet")......)
Have anyone been faced to this problem and could help me resolve this???

any help will be very appreciated thanks!!!!
adbeckett
Posts: 248
Online: User is Offline
3/05/2008 9:00 AM  
Well, it rather depends on what the function that is being used in the permuteDevice() is doing. This will be a SKILL function, and it needs to take into account the w, l and m of the transistors being combined appropriately, otherwise you'll get parameter mismatches. If it only looks at w and l, then it's not going to work properly...

Regards,

Andrew.
isazul
Posts: 26
Online: User is Offline
3/05/2008 9:15 AM  
This is the DivaLVS rules file I  use.
 Are the pemuteDevice statement wrong??

Thanks

Attachment: divaLVS_Rules.doc
adbeckett
Posts: 248
Online: User is Offline
3/05/2008 9:25 AM  
Not sure why you had to put the rule file into a Word document - a text file would be sufficient - just makes it harder to read...

Anyway, from a quick glance through the file, it appears to be checking and combining m.

So I would suggest you check with whoever you get the design kit and rules from, or contact Cadence customer support. Most likely they'll need to see the design data to see what's wrong - it's hard to figure it out without seeing the whole picture.

There's no fundamental tool reason why this shouldn't work. You might want to also check that the netlists you're getting for both the schematic and layout have the parameters w,l and m in them for these transistors (you can access these netlists from the LVS form).

Regards,

Andrew.
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