ADP3367

REV. 0

–5–

APPLICATIONS INFORMATION

Circuit Configurations

For a fixed +5 V output the SET input should be grounded, and

no external resistors are necessary. This basic configuration is

shown in Figure 8. The input voltage can range from +5.15 V

to +16.5 V, and output currents up to 300 mA are available

provided that the maximum package power dissipation is not

exceeded.

IN

OUT

GND

SET

SHDN

ADP3367

+5V

OUTPUT

C1

10µF

++

Figure 8. Fixed +5 V Output Circuit

Output Voltage Setting

If the SET input is connected to a resistor divider network, the

output voltage is set according to the following equation:

R1

+ R2

R1

IN

OUT

GND

SET

SHDN

ADP3367

+

R1

R2

C1

10µF

Figure 9. Adjustable Output Circuit

The resistor values may be selected by first choosing a value for

R1 and then selecting R2 according to the following equation:

R2

= R1×

− 1









The input leakage current on SET is 10 nA maximum. This

allows large resistor values to be chosen for R1 and R2 with

little degradation in accuracy. For example, a 1 M

Ω resistor

may be selected for R1, and then R2 may be calculated accord-

ingly. The tolerance on SET is guaranteed at less than

±25 mV,

so in most applications fixed resistors will be suitable.

Shutdown Input (SHDN)

The SHDN input allows the regulator to be switched off with a

logic level signal. This will disable the output and reduce the

current drain to a low quiescent (0.75

µA maximum) current.

This is very useful for low power applications. Driving the

SHDN input to greater than 1.5 V places the part in shutdown.

If the shutdown function is not being used, then SHDN should

be connected to GND.

Low Supply or Low Battery Detection

The ADP3367 contains on-chip circuitry for low power supply

or battery detection. If the voltage on the LBI pin falls below

the internal 1.255 V reference, then the open drain output LBO

will go low. The low threshold voltage may be set to any voltage

above 1.255 V by appropriate resistor divider selection.

R3

= R4 ×

V

BATT

V

LBI

−1









the desired low voltage threshold.

Since the LBI input leakage current is less than 10 nA, large

values may be selected for R3 and R4 in order to minimize

loading. For example, a 6 V low threshold, may be set using

10 M

Ω for R3 and 2.7 MΩ for R4.

The LBO output is an open-drain output that goes low sinking

current when LBI is less than 1.255 V. A pull-up resistor of

10 k

Ω or greater may be used to obtain a logic output level with

IN

OUT

LBO

ADP3367

C1

10µF

+

10k

Ω

LBI

GND

SET

SHDN

R3

R4

LOW BATTERY

STATUS OUTPUT

Figure 10. Low Battery/Supply Detect Circuit

Dropout Detector

The ADP3367 features an extremely low dropout voltage mak-

ing it suitable for low voltage systems where headroom is

limited. A dropout detector is also provided. The dropout

detector output, DD, changes as the dropout voltage approaches

its limit. This is useful for warning that regulation can no longer be

maintained. The dropout detector output is an open collector out-

put from a PNP transistor. Under normal operating conditions

with the input voltage more than 300 mV above the output, the

PNP transistor is off and no current flows out the DD pin. As the

voltage differential reduces to less than 300 mV, the transistor

switches on and current is sourced. This condition indicates that

regulation can no longer be maintained. Please refer to Figure 4 in

the “Typical Performance Characteristics.” The current output

can be translated into a voltage output by connecting a resistor

from DD to GND. A resistor value of 100 k

Ω is suitable. A digital

status signal can be obtained using a comparator. The on-chip

comparator LBI may be used if it is not being used to monitor a

battery voltage. This is illustrated in Figure 11.