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LTC3805-5 Minimum Startup Voltage (Vcc)

I am  unable to get the LTC3805 to start at any voltage less that 8.6V.  I've played with a number of variation of the downloadable demo circuit on the tools and simulations page at, and the schematic for the 12V output demo circuit 1576A at

Is it possible there is a problem with the model?  (Don't see a version number in LTSpice Help->About, but date is Jan 22, 2020).

In the screen shot below I've replaced the Vcc input resistor with a "low impedance source" per the data sheet, likewise dropped the RUN input resistor, and disconnected the soft-start cap.  Multiple variations on connecting/disconnecting, and modifying values have not produced startup at less than the 8.6V shown.  As mentioned I've also implemented a version emulating values in the 1576A demo circuit schematic without startup at less than 8.6V.

Any other thoughts welcome.

Dazed and confused,


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