SNVS953G December 2012 – May 2021 LM25018
At the minimum input voltage, the maximum switching frequency of LM25018 is restricted by the forced minimum off-time (TOFF(MIN)) as shown in Equation 10.
Similarly, at maximum input voltage, the maximum switching frequency of LM25018 is restricted by the minimum TON as shown in Equation 11.
Resistor RON sets the nominal switching frequency based on Equation 12.
Operation at high switching frequency results in lower efficiency while providing the smallest solution. For this example, 440 kHz was selected as the target switching frequency. The calculated value of RON = 253 kΩ. The standard value for RON = R3 is 237 kΩ is selected.