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TINA/Spice/LP2998: TINA Convergence problem

Joel Brown
Prodigy 190 points
Part Number: LP2998
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

I keep getting convergence problem, especially if I change anything.

LP2998.TSC

  • 0
    TI__Intellectual 835 points

    Hi Joel,

    There is a problem is the input timing given in this schematic.

    AVIN is at 0V and rises at a slower slew rate to 3.3V (rise time of 10us) while the gate voltage of mosfet T2 has a much faster slew rate (rise time of 10ns) So T2 tries to force AVIN node voltage of 0V at VTT node while the model internally tries to increase it above 0V. Hence the convergence failure.

    I have 2 potential solutions available. I have tested both and they work fine.

    1. Use a DC voltage of 3.3 at AVIN instead of step pulse. This can be used to observe steadystate behaviour.

    2. Add a delay at gate of T2 of more than 10us (say 20us or more).  This can be used to observe startup behaviour.

    Please find the .TSC file with setting for option 2 below. LP2998_modified.TSC

    Do let me know if anything else is required.

    Regards,

    Abhisek