SBVS336A September 2021 – May 2022 TPS7A94
If the input voltage is lower than the nominal output voltage plus the specified dropout voltage, but all other conditions are met for normal operation, the device operates in dropout mode. In this mode, the output voltage tracks the input voltage. During this mode, the transient performance of the device becomes significantly degraded because the pass transistor is in the ohmic or triode region, and acts as a switch. Line or load transients in dropout can result in large output-voltage deviations.
While in dropout, if a heavy load transient event forces VIN < VOUT(NOM) + 90 mV or VIN < VNR/SS + 20 mV, the device restarts to prevent the output voltage from overshooting to protect the device and load.
When the input voltage returns to a value greater than or equal to the nominal output voltage plus the dropout voltage (VOUT(NOM) + VDO), the output voltage can overshoot for a short period of time while the device pulls the pass transistor back into the linear region.
For additional information, see the Section 8.1.1 section.