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Workarounds for Flawed Abut functions

Cdub

I have experienced a similar problem as this person where the tsabutfunction doesn't work well when the mosfet instance has a multiplier variable greater than 1. The PDK says this is a known issue, there recommendation is to use parallel mosfet's instead. I'm working with 10 parallel mosfet and would rather not place all 10 on the schematic, plus I might change them depending on simulations after layout. I'm wondering if there is a better work around. I have tried to place mosfet's in the layout that haven't been binded to an instance, but I can't figure out how to abut them. Any suggestions?

Thanks!

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  • Andrew Beckett

    I would contact the foundry because I can't see a good reason for this.

    A workaround might be to place them in the schematic as M1<0:9> so you don't have to have multiple physical instances in the schematic, but this really should not be necessary. I can't help much more without seeing the actual issue, but if separate instances works then this might solve it.

    Abutment won't really work unless there's a schematic binding, since it wouldn't know what the connectivity is and so know what is a valid target for abutment.

    Andrew.

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  • Andrew Beckett

    I would contact the foundry because I can't see a good reason for this.

    A workaround might be to place them in the schematic as M1<0:9> so you don't have to have multiple physical instances in the schematic, but this really should not be necessary. I can't help much more without seeing the actual issue, but if separate instances works then this might solve it.

    Abutment won't really work unless there's a schematic binding, since it wouldn't know what the connectivity is and so know what is a valid target for abutment.

    Andrew.

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