Regarding the LTC7899, the DRVCC voltage is adjustable via the DRVSET pin.
Is the charge pump output voltage also adjustable according to the DRVSET setting, or is it fixed at a certain voltage?
I also ran an LTspice simulation under a 100% duty-cycle condition (Vin > Vout).
However, it appears that the charge pump function is not currently implemented in the LTspice model.