8.1.5 Behavior During Transition From Dropout Into Regulation

Some applications may have transients that place this device into dropout, especially when this device can be powered from a battery with relatively high ESR. The load transient saturates the output stage of the error amplifier when the pass element is driven fully on, making the pass element function like a resistor from V_IN to V_OUT. The error amplifier response time to this load transient is limited because the error amplifier must first recover from saturation and then place the pass element back into active mode. During this time, V_OUT overshoots because the pass element is functioning as a resistor from V_IN to V_OUT.

When V_IN ramps up slowly for start-up, the slow ramp-up voltage may place the device in dropout. As with many other LDOs, the output can overshoot on recovery from this condition. However, this condition is easily avoided through the use of the enable signal.

If operating under these conditions, apply a higher dc load or increase the output capacitance to reduce the overshoot. These solutions provide a path to dissipate the excess charge.