Because the TPS7A43 has two output rails (MID_OUT and OUT), the device can be in either V_{DO(MID_OUT)} or V_DO(OUT), or in both depending on the input voltage level while all other conditions are met for normal operation. When the input voltage drops to lower than V_{MID_OUT(nom)} + V_{DO(MID_OUT)}, the device is in V_{DO(MID_OUT)} dropout. During this rail dropout, V_{MID_OUT} tracks V_IN and the transient performance of V_{MID_OUT} becomes significantly degraded because the pass transistor is in the ohmic or triode region, and acts as a switch. The MID_OUT rail line or load transients in the V_{DO(MID_OUT)} dropout can result in large V_{MID_OUT} deviations. When the device is still in V_{DO(MID_OUT)} and when V_IN is higher than V_OUT(nom) + V_DO(OUT), V_OUT is in regulation and is not in V_DO(OUT) dropout. When V_IN drops below V_OUT(nom) + V_DO(OUT), V_OUT is no longer in regulation and transient performance becomes significantly degraded.

When the device is in a steady dropout state (when the device is in both V_{DO(MID_OUT)} and V_DO(OUT) dropout, directly after being in a normal regulation state, but not during start up), the pass transistor is driven into the ohmic or triode region. When the input voltage returns to a value greater than or equal to V_{MID_OUT(nom)} + V_{DO(MID_OUT)} and greater than V_OUT(NOM) + V_DO, the output voltage (OUT) can overshoot for a short period of time while the device pulls the pass transistor back into the linear region.