AP7167

1.2A LOW DROPOUT REGULATOR WITH POK

AP7167 Rev. 2

9 of 11

JANUARY 2008

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Application Note

(Continued)

No Load Stability

Other than external resistor divider, no minimum load is

required to keep the device stable. The device will

remain stable and regulated in no load condition.

ENABLE/SHUTDOWN Operation

The AP7167 is turned on by setting the EN pin high, and

is turned off by pulling it low. If this feature is not used,

the EN pin should be tied to IN pin to keep the regulator

output on at all time. To ensure proper operation, the

signal source used to drive the EN pin must be able to

swing above and below the specified turn-on/off voltage

thresholds listed in the Electrical Characteristics section

POWER-OK

The Power-Ok (POK) pin is an active high open-drain

output. It can be connected to any 5.5V or lower rail

through

an

external

pull-up

resistor.

The

recommended sink current of POK pin is up to 4mA, so

the pull-up resistor for POK should be in the range of

10k

Ω to 1MΩ. If output voltage monitoring is not needed,

the POK pin can be left floating.

Current Limit Protection

When output current at OUT pin is higher than current

limit threshold, the current limit protection will be

triggered and clamp the output current to approximately

1.6A (1.2A min) to prevent over-current and to protect

the regulator from damage due to overheating.

Short Circuit Protection

When OUT pin is short-circuited to GND or OUT pin

voltage is less than 200mV, short circuit protection will

be

triggered

and

clamp

the

output

current

to

approximately

750mA.

This

feature

protects

the

regulator

from

over-current

and

damage

due

to

overheating.

Low Quiescent Current

The AP7167, consuming only around 150µA for all input

range and output loading, provides great power saving

in portable and low power applications.

Wide Output Range

The AP7167, with a wide output range of 0.8V to 5.0V,

provides a versatile solution for many portable and low

power applications.

Thermal Shutdown Protection

Thermal protection disables the output when the

junction temperature rises to approximately +155°C,

allowing the device to cool down. When the junction

temperature reduces to approximately +130°C the

output circuitry is enabled again. Depending on power

dissipation,

thermal

resistance,

and

ambient

temperature, the thermal protection circuit may cycle on

and off. This cycling limits the heat dissipation of the

regulator, protecting it from damage due to overheating.

Power Dissipation

The device power dissipation and proper sizing of the

thermal plane that is connected to the thermal pad is

critical to avoid thermal shutdown and ensuring reliable

operation. Power dissipation of the device depends on

input voltage and load conditions and can be calculated

by:

OUT

OUT

IN

D

xI

)

V

V

(

P

−

=

The AP7167 is available in the DFN3030-10 package

with exposed pad, which is the primary conduction path

for heat to the printed circuit board (PCB). The pad can

be connected to ground or be left floating; however, to

ensure the device will not overheat, it should be

attached to an appropriate amount of copper PCB area.

However, the maximum power dissipation that can be

handled by the device depends on the maximum

junction to ambient thermal resistance, maximum

ambient temperature, and maximum device junction

temperature, which can be approximated by the

equation below:

JA

A

A

D

R

)

T

C

150

(

)

T

(max@

P

θ

−

°

+

=