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Revision 1.9

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AS1363

Datasheet - Application In form atio n

9 Application Information

9.1 Dropout Voltage

Dropout is the input to output voltage difference, below which the linear regulator ceases to regulate. At this point, the output voltage change

follows the input voltage change. Dropout voltage may be measured at different currents and, in particular at the regulator maximum one. From

this is obtained the MOSFET maximum series resistance over temperature etc. More generally:

(EQ 2)

Dropout is probably the most important specification when the regulator is used in a battery application. The dropout performance of the

regulator defines the useful “end of life” of the battery before replacement or re-charge is required.

Figure 18. Graphical Representation of Dropout Voltage

regulated output voltage of the LDO is that obtained when there is 500mV (or greater) input-output voltage differential.

9.2 Efficiency

Low quiescent current and low input-output voltage differential are important in battery applications amongst others, as the regulator efficiency is

directly related to quiescent current and dropout voltage. Efficiency is given by:

Efficiency =

%

(EQ 3)

Where:

V

DROPOUT

I

LOAD

R

SERIES



=

Dropout

Voltage

100mV

V

LOAD

I

LOAD



V

I

LOAD

+



---------------------------------------

100

