6.4 Device Functional Modes

Table 6-1 provides a quick comparison between the normal and dropout modes of operation.

Table 6-1. Device Functional Mode Comparison

OPERATING MODE

PARAMETER

VIN

IOUT

Normal

VIN > VOUT(nom) + VDO

IOUT < ICL

Dropout

VIN < VOUT(nom) + VDO

IOUT < ICL

6.4.1 Normal Operation

The device regulates to the nominal output voltage under the following conditions:

• The input voltage is greater than the nominal output voltage plus the dropout voltage (VOUT(nom) + VDO)

• The output current is less than the current limit (IOUT < ICL)

• The device junction temperature is greater than –40°C and less than +125°C

6.4.2 Dropout Operation

If the input voltage is lower than the nominal output voltage plus the specified dropout voltage, the device

operates in dropout mode. However, make sure all other conditions are met for normal operation. In this mode,

the output voltage tracks the input voltage. During this mode, the transient performance of the device becomes

significantly degraded. The pass transistor is in the ohmic or triode region, and acts as a switch. Line or load

transients in dropout result in large output voltage deviations.

When the device is in a steady dropout state, the pass transistor is driven into the ohmic or triode region. This

state is defined as when the device is in dropout, directly after being in a normal regulation state, but not during

start up. Dropout occurs when VIN < VOUT(NOM) + VDO. When the input voltage returns to a value ≥VOUT(NOM) +

VDO, the output voltage overshoots for a short period of time. VOUT(NOM) is the nominal output voltage and VDO is

the dropout voltage. During this time, the device pulls the pass transistor back into the linear region.

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SLVSGU2F – FEBRUARY 2023 – REVISED AUGUST 2025

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