The on-time of the LM5160 high-side MOSFET is determined by the RON resistor and is inversely proportional to the input voltage (VIN). The inverse relationship with VIN results in a nearly constant frequency as VIN is varied. Calculate the on-time from Equation 3 with RON expressed in Ohms.
To set a specific continuous conduction mode switching frequency (FSW expressed in Hz), determine the RON resistor from Equation 4.
RON must be selected for a minimum on-time (at maximum VIN) greater than 150 ns for proper operation. This minimum on-time requirement limits the maximum switching frequency of applications with relatively high VIN and low VOUT.