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Differential .stb analysis by referencing terminals on an av_extracted view including devices with multiplier

DavidI
DavidI over 2 years ago

Hey,

I have the following situation:

1) I have a differential feedback system with MP0 and MP1 being the input transistors of my feedback amp

2) I do a differential .stb by referencing the gate terminals of my error amplifier. The reference looks like: /DUT/AMP/MP0/G and /DUT/AMP/MP1/G 

3) This is working fine and giving results like expected

4) Next step: I create an av_extracted view

5) The devices MP0 and MP1 have a multiplier of four so they get splitted into multiple instances in the av_extracted view, something like AMP\|MP0 , AMP\|MP0_1__rcx , AMP\|MP0_2__rcx , AMP\|MP0_3__rcx

6) in the .stb looking at the av_extracted view I put /DUT/AMP|MP0/G and /DUT/AMP|MP1/G as reference

7) the .stb results looks completly different

8) I assume 3/4 of the transistors  MP0 and MP1 are not evaluated as I can only probe a single gate terminal

So in short: I fail to do on terminal based .stb on an av_extracted view including devices with multipliers

This situation is very common in my everyday life and I hopped to get a proper .stb without schematic manipulation (e.g. with the rmetal plus deepprobe approach)

Does anyone know a solution?

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  • Andrew Beckett
    Andrew Beckett over 2 years ago in reply to Frank Wiedmann

    The single-ended solution is simpler than differential - it's effectively similar to what the save statement does - that can insert a probe point in a hierarchical node; for differential stability it's more complex and currently is limited to leaf instances.

    Andrew

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  • Frank Wiedmann
    Frank Wiedmann over 2 years ago in reply to Andrew Beckett

    Is there already a CCR requesting support for subcircuit terminals also for the differential stb analysis? If so, I would certainly want to file a duplicate for this.

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  • Andrew Beckett
    Andrew Beckett over 2 years ago in reply to Frank Wiedmann

    I'm not aware of one. I'm not sure it's possible, but that would need R&D to answer that.

    Andrew

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  • Frank Wiedmann
    Frank Wiedmann over 2 years ago in reply to Andrew Beckett

    CCR 2745599 has now been filed, requesting support for subcircuit terminals also for the differential stb analysis. Anyone who would also like to have this should ask Cadence Support to file a duplicate of this CCR on their behalf.

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