ZHCSEQ3D February 2016 – December 2022 LM5165
PRODUCTION DATA
As mentioned, the switching frequency of a COT-configured LM5165 is set by the on-time programming resistor at the RT pin. As shown by Equation 2, a standard 1% resistor of 133 kΩ gives a switching frequency of 230 kHz.
Note that at very low duty cycles, the minimum controllable on-time of the high-side MOSFET, TON(min), of 180 ns may affect choice of switching frequency. In CCM, TON(min) limits the voltage conversion step-down ratio for a given switching frequency. The minimum controllable duty cycle is given by Equation 9:
Given a fixed TON(min), it follows that higher switching frequency implies a larger minimum controllable duty cycle. Ultimately, the choice of switching frequency for a given output voltage affects the available input voltage range, solution size and efficiency. The maximum supply voltage for a given TON(min) before switching frequency reduction occurs is given by Equation 10.