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Best way to mark analogue differential pins as such in Virtuoso Schematic Editor ?

Herge

Background

In VSE one can assign properties to pins that annotate their "role". The system provides built-in "signal types" :  analog, clock, ground, power, reset, scan, supply, tieHi, tieLo, and tieOff. Besides the signalType, there are also power and ground sensitivity properties allowing to annotate from which supply / ground the particular pin is driven or referenced. These properties are sufficient for our purpose of automating the process of fault injection in analogue circuits, but only in the case of single-ended pins.

For injecting failure modes on the differential pins of analogue blocks in an automated fashion, we need a way to represent a new pin type (netType) "differential-analogue". We also need to annotate those pins that they belong to a given differential pair (requiring a new custom property) and to label the supply sensitivities (which has no special requirement beyond what is already available.

Question

What is the best / most practical way to mark analogue differential pins with properties denoting the following :

  1. Their analogue nature (not digital) ?
  2. Their differential character ?
  3. Their membership to a given differential pair ?
  4. Eventually their polarity : positive or negative ?

Additional considerations

  • The best solution would be "compact" in terms of the perimeter of tools (and licenses) required. So if it can efficiently be done with pin properties and does not require to introduce constraints, then the pin properties solution is the more compact and preferred one.
  • The best solution would be extensible (support efficient extensions for example to introduce constraints of electrical, routing or layout type).

Discussion

Is the creation of a custom netType the best solution  in this case ?

Are other complementary measures necessary ?

Why do we see that most discussions with the term  "differential" are in the PCB design fora and not so much  on the IC design side ?

Parents

  • This rather depends on what you want to do with the information you're storing. The signal types are fixed but the point here is that you're defining a pair of pins somehow as differential. So presumably you want to mark them as differential so that some tool can consume that information - without knowing the tool it's hard to suggest the right way to do this.

    The schematic editor does have a "differential" mode (rarely used) which allows you to expand single nets into a two bit vector for the differential nets. I'm not sure that's what you want (schematic differential boolean t in the .cdsenv).

    I've no idea why why most discussions related to differential are in the PCB fora. Differential design is done everyday in the Custom IC design tools, but maybe there generally doesn't need to be any specific questions on it.

    I would suggest you contact customer support so that an application engineer can have a discussion about the bigger picture and what you are hoping to achieve.

    Regards,

    Andrew.

Reply

  • This rather depends on what you want to do with the information you're storing. The signal types are fixed but the point here is that you're defining a pair of pins somehow as differential. So presumably you want to mark them as differential so that some tool can consume that information - without knowing the tool it's hard to suggest the right way to do this.

    The schematic editor does have a "differential" mode (rarely used) which allows you to expand single nets into a two bit vector for the differential nets. I'm not sure that's what you want (schematic differential boolean t in the .cdsenv).

    I've no idea why why most discussions related to differential are in the PCB fora. Differential design is done everyday in the Custom IC design tools, but maybe there generally doesn't need to be any specific questions on it.

    I would suggest you contact customer support so that an application engineer can have a discussion about the bigger picture and what you are hoping to achieve.

    Regards,

    Andrew.

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