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leaf cell issue with using diffstbprobe

kenc184

I have a fully differential amplifier design and wish to look at gain/phase.  I've instantiated diffstbprobe between outputs and inputs, and on the prompts, selected I3/IN1 and I3/IN2 as the "probe Instance/terminal" 1 and 2.

Spectre dies with the following error

 Cannot run the simulation because the leaf instance 'I3' could not be found. Specify a valid leaf instance terminal name for the stb analysis and rerun the simulation

Any ideas?  I don't recall ever having a similar issue with cmdmprobe so I assume something somewhere is not set up correctly.

Parents
  • Andrew Beckett

    There is a very recent addition (in IC618/ICADVM201 ISR21) which allows you to do differential/common-mode stability without needing to insert a diffstbprobe. This also requires SPECTRE20.1 ISR8 or later. So there are two flows:

    1. You have a diffstbprobe, in which case the Probe Instance/Terminal1 should simply be the instance of the diffstbprobe itself (not a terminal of the diffstbprobe). The second field (Probe Terminal2) should be left blank.
    2. Alternatively you can point at two separate instance terminals and if that is done a diffstbprobe is effectively inserted within the simulator (at least, you can think of it being done this way). In this case the two fields become the instance terminals - but there is a requirement that the instance terminals are on leaf devices (i.e. primitive devices) as this means there is only a single current flow that is being monitored. This is particularly useful for post-layout flows as it avoids you having to do all the messing around with deepprobe as I outline in How to perform a stability (stb) analysis on a loop within an extracted view or DSPF file 

    You're trying to use the first flow above, but by entering the fields for the second flow - and that won't work.

    I do agree that the UI is a little confusing now. I'm going to update the article above but also suggest to R&D that they improve the usability of the form to make it clearer.

    Regards,

    Andrew

Reply
  • Andrew Beckett

    There is a very recent addition (in IC618/ICADVM201 ISR21) which allows you to do differential/common-mode stability without needing to insert a diffstbprobe. This also requires SPECTRE20.1 ISR8 or later. So there are two flows:

    1. You have a diffstbprobe, in which case the Probe Instance/Terminal1 should simply be the instance of the diffstbprobe itself (not a terminal of the diffstbprobe). The second field (Probe Terminal2) should be left blank.
    2. Alternatively you can point at two separate instance terminals and if that is done a diffstbprobe is effectively inserted within the simulator (at least, you can think of it being done this way). In this case the two fields become the instance terminals - but there is a requirement that the instance terminals are on leaf devices (i.e. primitive devices) as this means there is only a single current flow that is being monitored. This is particularly useful for post-layout flows as it avoids you having to do all the messing around with deepprobe as I outline in How to perform a stability (stb) analysis on a loop within an extracted view or DSPF file 

    You're trying to use the first flow above, but by entering the fields for the second flow - and that won't work.

    I do agree that the UI is a little confusing now. I'm going to update the article above but also suggest to R&D that they improve the usability of the form to make it clearer.

    Regards,

    Andrew

Children
  • kenc184
    in reply to Andrew Beckett

    Thanks very much Andrew, that wasn't obvious!

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