SNVS690I January 2011 – August 2021 LMZ14201H
Current limit detection is carried out during the OFF-time by monitoring the current in the synchronous MOSFET. Referring to the Section 7.2, when the top MOSFET is turned off, the inductor current flows through the load, the PGND pin and the internal synchronous MOSFET. If this current exceeds the ICL value, the current limit comparator disables the start of the next ON-time period. The next switching cycle will occur only if the FB input is less than 0.8 V and the inductor current has decreased below ICL. Inductor current is monitored during the period of time the synchronous MOSFET is conducting. So long as inductor current exceeds ICL, further ON-time intervals for the top MOSFET will not occur. Switching frequency is lower during current limit due to the longer OFF-time.
The DC current limit varies with duty cycle, switching frequency, and temperature.