SNVS788H January 2012 – August 2021 LM5019
The LM5019 contains an intelligent current limit off-timer. If the current in the buck switch exceeds 240 mA, the present cycle is immediately terminated, and a non-resetable off-timer is initiated. The length of off-time is controlled by the FB voltage and the input voltage VIN. As an example, when FB = 0 V and VIN = 48 V, the maximum off-time is set to 16 μs. This condition occurs when the output is shorted, and during the initial part of start-up. This amount of time ensures safe short circuit operation up to the maximum input voltage of 100 V.
In cases of overload where the FB voltage is above zero volts (not a short circuit), the current limit off-time is reduced. Reducing the off-time during less severe overloads reduces the amount of foldback, recovery time, and start-up time. The off-time is calculated from Equation 4:
The current limit protection feature is peak limited. The maximum average output will be less than the peak.