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LVS - numbers of Vcc & Gnd

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crystal

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The layout drawn has numerous Vcc & Gnd (i.e Vcc1, Vcc2 and Gnd1, Gnd2).
When one is doing LVS (in cadence) - comparing schematic with extracted view of layout, how would the tool (Diva) know about the numbers of the Vcc & Gnd as in schematic, there's only one Vcc and Gnd.

Anybody can advise?
 

skal81

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I think several Vdd are not a problem. You just need to have different pins.
For ground the problem is that all are connected by the substrate. So an error will show up.
You can use a layer called PSUB2 (in TSMC technology). It's a dummy layer to say the LVS soft that it is a different ground from the substrate.
 

sambireddy

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the tool finds the number of gnds and vdd by keeping track of the number of terminals to which the subject is connected. it takes into consideration the number of nets connected to the vdd or gnd.
 

layout_designer

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If the schematics and layouts are done in heirarchical way, the tool recognises the vdds and gnds locally and globally.
 

sambireddy

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The different terms for different vcc's and grounds is enough for the tool to understand that there are many powers in the circuit. and iif the grounds are separately connected then u have to use a special layer specified by the foundry to make the tool know that the substrates have different grounds.
 

omsi

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hi,
there is a option in to short all vcc's and ground's virtually.
suppose if u r using calibre lvs tool,in rule file there will be a syntax that
VIRTUAL PORTS XXX XXX
if u define the ports like
VIRTUAL PORTS vcc vcc1
the lvs will be runned considering the vcc and vcc1 are shorted virtually but not actually.
hope u got .
 

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