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Which simulator is best to use for Mixed-Signal Simulation?

Kabal

For example I can have some HDL design compiled and implemented in Encounter Digital Implementation, then I can have that design imported in Virtuoso Encironment as a layout or higher level schematics symbol to be used together with another part of design which is analog.

However, which simulator is it better then to use to simulate the whole thing, by whole thing I mean my relatively big autoplaced/autorouted digital block from encounter + Hand made analog circuits?

For example if I want to just verify my analog-only blocks I'll use spectre, if I want to verify my digital logic and run timing analysis I'll use RC compiler + INCISIVE. But what about combined circuits simulation? 

Obviously, using Spectre would take like infinite time (I remember simulating relatively small hand made digital circuits together with analog blocks, it took forever).

So which simulator, or approximate design/simulation flow should I look at then?

 

thanks 

  • Sorry I am a little confused now. The datasheet of "AMS Designer" shows it as something what has Spectre and INCISIVE in it.
    Well, I do have INSCISIVE, that is for purely HDL simulation. And I do have Spectre. But Spectre is terribly slow at simulating huge mixed-signal designs.

    My question then is, what is precise name of AMS Designer package which appears in "Software Search" directory with that Installscape tool? How to install it and get that simulator working (again, *not* Spectre or INSCIVE)

  • AMS Designer is a mixed analog-digital simulator which uses technology from Spectre (or APS) or Ultrasim together with the digital ncsim solver. It's delivered in the INCISIV stream, and it is a single-executable simulator which has two "solvers" inside. The analog solver is spectre/APS/Ultrasim, and the digital "solver" is ncsim.

    The idea is that portions of the design which are pure digital are simulated using the digital solver - and so are simulated in Verilog/VHDL/SystemVerilog; the analog portions are simulated using the analog solver. The two solvers work together and share information in memory to ensure that they are synchronized. You can also write mixed-signal behavioural models using Verilog-AMS or VHDL-AMS which allow models with both analog and digital behaviour in the same model. There's also a concept of "connect modules" (sometimes known as "interface elements") which control how analog and digital signals are converted between the two domains.

    Speed of simulation comes from the fact that:

    • You are not simulating the entire circuit at transistor level - you are using Verilog/VHDL/SystemVerilog descriptions of the gate level (or higher) blocks, and these can be simulated using an event-driven approach
    • You are simulating only the analog portions in the analog solver - and you can use behavioural models to speed this up further still.
    • You can write "real number" models which if used everywhere can mean that everything can be simulated in the event-driven engine and the analog solver may not be needed at all.
    • You can use APS to further speed up the analog parts.

    So install AMS Designer from the INCISIV stream - that's where to start. There are quick start tutorials in the installation too which would help...

    Regards,

    Andrew.

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