LP38692 and LP38693 Foldback current limit

It means that if the Enable function is de-asserted and Cout is discharged, and then the Enable function is re-asserted, the current from the input capacitor to the output capacitor is not limited by the fold-back current-limit circuitry. This is the same effect as 'in-rush current'. Depending on Vin, Cin, and Cout values, the in-rush current can exceed 1A for 5 to 50 micro-sec, with a peak current possibly in excess of 2A for a few micro-secs. After the in-rush current event has ended, the normal fold-back current-limiting will be active and will behave normally.

Typically the bulk of the in-rush current would be pulled from the input capacitor with minimal input voltage droop. However, in some applications where the input supply is not robust, or the Cin value is small, or the Cout value is large, there will be a noticeable input voltage droop. In systems where Cout is large and the Fold-Back Current-Limiting is expected to provide a 'soft-start' effect, this effect will be lost with the second, and any subsequent, assertions of Enable.

This condition is only relevant at the time of the second, and any subsequent, assertions, of Enable. If the device is operating steady state the current limiting behavior will behave normally.

If Vin is taken low, the portion of the current limit circuitry associated with this issue is essentially 'reset'.