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Analog Layout: interdigitization

luca magnelli

Hi,

I'm approaching to analog layout with Virtuoso XL. I have to realize the layout of a simple current mirror (2 transistors) and, for matching purposes, I'd like to realize it using an inter-digitized (or common centroid) arrangements.

There is a way, in Virtuoso XL, to merge 2 or more instances in order to form an inter-digitated one? It seems to me that, starting from a schematic entry and generating the layout from this source, Virtuoso XL only gives separate instances and the only thing to do is routing them.

Can anyone show me the procedure for activating transistors inter-digitization in Virtuoso XL?

Thanks,

Luca

Parents

  • An automatic interdigitation algorithm is pretty complex unless you use the natural capabilities of abutment in aligningthe cells. Using dbMoveFig or rodAlign on a cell does not trigger abutment during a SKILL program but if you follow the move/align command immediately with hiUpdate(), the abutment/spacing will automatially trigger. Thus, you are spared some of the messy calculations for the pcell parameters as the tool will automatically send the abutment program the correct values. Of course, your abutment program has to be working correctly.

    I do not have the algorithm I used before Cadence bought NeoLinear as it was hard to maintain and NeoCell's capabilities were better (in IC6.1 especially).

     Ted

Reply

  • An automatic interdigitation algorithm is pretty complex unless you use the natural capabilities of abutment in aligningthe cells. Using dbMoveFig or rodAlign on a cell does not trigger abutment during a SKILL program but if you follow the move/align command immediately with hiUpdate(), the abutment/spacing will automatially trigger. Thus, you are spared some of the messy calculations for the pcell parameters as the tool will automatically send the abutment program the correct values. Of course, your abutment program has to be working correctly.

    I do not have the algorithm I used before Cadence bought NeoLinear as it was hard to maintain and NeoCell's capabilities were better (in IC6.1 especially).

     Ted

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