Diodes AP7168 Manuel d'utilisateur télécharger pdf (Page 8)

AP7168

1.2A LOW DROPOUT REGULATOR WITH POK

AP7168

Document number: DS32019 Rev. 2 - 2

8 of 11

www.diodes.com

September 2010

NEW PRODUCT

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 AP7168 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

under V

and V

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 10kΩ 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 AP7168, 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 AP7168, 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 +145°C, allowing the

device to cool down. When the junction temperature

reduces to approximately +120°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:

OUTOUTIND

xI)VV(P −

The AP7168 is available in the SO-8EP packages, both

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:

)TC150(

)T(max@P

−

°+

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Diodes AP7168 Manuel d'utilisateur Page 8

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