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LM311: Spice model does not match the specs in the datasheet

gchaconr
Intellectual 645 points
Part Number: LM311
Other Parts Discussed in Thread: LM111-N, LM111, TINA-TI

Downloaded the Pspice model of LM311 to use it in ADS, and the problem I am facing is the response time (low-to-high and high-to-low) from simulation does not match the information from the datasheet. From simulation is about 40ns, while datasheet indicates over 100ns.

Am I setting something wrong in the simulation?

Thanks,

Gus 

  • 0
    TI__Guru 62536 points

    Hello Gus,

    Which model did you use? There are two available.

    The model on the LM311 page (SLCJ012), which unzips to "LM311.301", is a old transistor based model that does not model the actual behavior very well, particularly the overdrive vs prop delay behavior. The ".301" means it models the behavior at 30V supply.

    http://www.ti.com/lit/zip/slcj012

    The LM111-N model (SNOM024) is newer and attempts to model the slew vs Prop delay, but still not very well:

     http://www.ti.com/lit/zip/snom264

    Note: TI SPICE models model typical behavior at room temp, so the LM311 and LM111-N "typical" behavior is the same. The "-N" is the National version.

    I'm seeing about ~60ns in TINA-TI for the LM111 model, and ~40ns for the LM311 model.

    A new model was requested, but it is still a few weeks from release.

    The actual device may reach about 80-90ns with a large (>1V) input signal. The 100ns datasheet spec is with a relatively small 5mV overdrive and 5pF cap load.

    The fall-time will be faster, but the rise-time will be dependent on the pull-up resistor size and capacitive load (creates a RC time constant).