Abstract: An analytical model was proposed to calculate the minimum startup voltage of a boost DC/DC converter under a constant current load. The factors, such as the current load, the parasitic parameters, the saturation current and on-resistance of the power switch, the switching frequency, and the minimum startup voltage, etc., which affect the startup capability of the boost DC/DC converter were analyzed with a steady-state analysis method. The model was applied to the design of a boost DC/DC converter with a 0.6 μm CMOS process, and the maximum error of the minimum startup voltage calculated by the proposed model was 4.5% compared with that by the HSPICE simulator