Minimum ON-time, T_{ON_MIN}, is the smallest duration of time that the HS switch can be on. T_{ON_MIN} is typically 84 ns in the TPS2585x-Q1. Minimum OFF-time, T_{OFF_MIN}, is the smallest duration that the HS switch can be off. T_{OFF_MIN} is typically 81 ns in the TPS2585x-Q1. In CCM (FPWM) operation, T_{ON_MIN} and T_{OFF_MIN} limit the voltage conversion range given in a selected switching frequency.

The minimum duty cycle allowed is:

And the maximum duty cycle allowed is:

Given fixed T_{ON_MIN} and T_{OFF_MIN}, the higher the switching frequency, the narrower the range of the allowed duty cycle.

Given an output voltage, the choice of the switching frequency affects the allowed input voltage range, solution size, and efficiency. The maximum operation supply voltage can be found by:

Equation 7.

At lower supply voltage, the switching frequency is limited by T_{OFF_MIN}. The minimum V_IN can be approximated by:

Equation 8.

Considering power losses in the system with heavy load operation, V_{IN_MAX} is higher than the result calculated in Equation 7.

If minimum ON-time or minimum OFF-time do not support the desired conversion ratio, frequency is reduced, automatically allowing regulation to be maintained during load dump and with very low dropout during cold crank even with high operating-frequency setting.