7.3.3 Dropout Voltage

The TPS735-Q1 family of devices uses a PMOS pass transistor to achieve low dropout. When (V_IN – V_OUT) is less than the dropout voltage (V_DO), the PMOS pass device is in the linear region of operation and the input-to-output resistance (R_(IN/OUT)) of the PMOS pass element. V_DO scales with the output current because the PMOS device behaves like a resistor in dropout.

As with any linear regulator, PSRR and transient response are degraded when (V_IN – V_OUT) approaches dropout. This effect is shown in the Typical Characteristics section (see Figure 8 through Figure 10).