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AS1369

Datasheet - Application In form atio n

Figure 47. Graphical Representation of Dropout Voltage

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

8.2 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:

IQ = Quiescent current of LDO

8.3 Power Dissipation

Maximum power dissipation (PD) of the LDO is the sum of the power dissipated by the internal series MOSFET and the quiescent current

required to bias the internal voltage reference and the internal error amplifier, and is calculated as:

Watts

(EQ 4)

Internal power dissipation as a result of the bias current for the internal voltage reference and the error amplifier is calculated as:

Watts

(EQ 5)

Total LDO power dissipation is calculated as:

Watts

(EQ 6)

Dropout

Voltage

100mV

V

LOAD

I

LOAD



V

I

LOAD

+



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

100



PD

MAX



I

LOAD MAX



=

V

IN MAX



V

OUT MIN



–



PD

MAX



V

IN MAX

=

PD

MAX



PD

MAX

 PD

MAX



+

Bias



=