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TINA/Spice/LP5907UV-3.3EVM: Linear TINA SPICE model with noise for LP5907

FarronDacus
Intellectual 780 points

Part Number: LP5907UV-3.3EVM

Tool/software: TINA-TI or Spice Models

Hello:  I need the ability to simulate the voltage noise spectral density in the LP5907 low noise regulator as part of a filtered reference noise chain.  I only see transient SPICE models being available for this part.  Is there a linear model that will generate correct noise in an AC noise simulation?  If not, can one be provided?  Thanks....

  • 0
    TI__Guru 55940 points

    Hi Farron,

    Unfortunately we our current spice models do not have the capability of modeling noise.  We do not have any additional models available.

    For linear regulators our noise specification includes only what is generated by the regulator.  The primary source of noise is the internal bandgap.  PSRR is the term that covers the regulators ability to block ripple present on the input rail.

    Due to the LP5907 design topology, the only application condition Iout.  Please note that our datasheet does provide a plot of noise across different output currents.

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Intellectual 780 points

    Hi Ryan:

    Thanks for that prompt reply.  In checking the regulator models available from TINA, I note they are all in fact either Zener diodes, regulators whose noise is not specified, or specifically transient models. 

    However, TINA does have TI op amp models that do have noise.  It would seem that TI could, if desired, put a macro model for the band gap reference noise in a linear regulator regulator model.  It would certainly be handy, since then whole noise chains could have end to end noise simulation.  Sure, you can manually via simulated transfer functions and noise levels in op amp circuitry calculate the noise from a regulator whose noise is in the data sheet after filtering at the end of a noise filter chain.  It's just a whole lot more trouble than doing it in SPICE.

    Part of the modeling problem is that after all these decades of SPICE, most versions still do not have simple 1/f noise models.  It would not be much trouble to code an easy to use f^(-n) flicker noise source into SPICE, which if n is variable lets you simulate 1/f, 1/f^2, or any other noise shape.  Then we would not need to ask for the regulator noise model ,as we could create an accurate noise source easily to represent the noise of any regulator or any op amp. 

    Thanks,

    Farron