AP7365 datasheet(11/20 Pages) DIODES

11 / 20 page

AP7365

600mA, Low Quiescent Current, Fast Transient

Low Dropout Linear Regulator

AP7365

Document number: DS32260 Rev. 2 - 2

11 of 20

www.diodes.com

September 2010

Application Note

Input Capacitor

A 1

μF ceramic capacitor is recommended between IN and

GND pins to decouple input power supply glitch and noise.

The amount of the capacitance may be increased without

limit. This input capacitor must be located as close as

possible to the device to assure input stability and reduce

noise. For PCB layout, a wide copper trace is required for

both IN and GND pins. A lower ESR capacitor type allows

the use of less capacitance, while higher ESR type

requires more capacitance.

Output Capacitor

The output capacitor is required to stabilize and improve

the transient response of the LDO. The AP7365 is stable

with very small ceramic output capacitors. Using a ceramic

capacitor value that is at least

1μF with ESR > 15mΩ on

the output ensures stability. Higher capacitance values

help to improve line and load transient response. The

output capacitance may be increased to keep low

undershoot and overshoot. Output capacitor must be

placed as close as possible to OUT and GND pins.

Region of Stable COUT ESR vs. Load Current

0.001

0.01

0.1

100

200

300

400

500

600

Load Current (mA)

Adjustable Operation

The AP7365 provides output voltage from 0.8V to 5.0V

through external resistor divider as shown below.

1uF

GN D

OU T

E nable

AD J

1uF

V IN

V OUT

A P 7365

The output voltage is calculated by:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

REF

OUT

Where VREF=0.8V (the internal reference voltage)

Rearranging the equation will give the following that is

used for adjusting the output to a particular voltage:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

REF

OUT

To maintain the stability of the internal reference voltage,

R2 need to be kept smaller than 80kΩ.

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.

ON/OFF Input Operation

The AP7365 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 VIL and VIH.

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 1.4A to prevent

over-current and to protect the regulator from damage due

to overheating.

Short Circuit Protection

When OUT pin is short-circuit to GND, short circuit

protection will be triggered and clamp the output current to

approximately 240mA. This feature protects the regulator

from over-current and damage due to overheating.

Thermal Shutdown Protection

Thermal

protection

disables

the

output

when

the

junction temperature

rises

approximately

+145°C,

allowing the device to cool down. When the junction

temperature

reduces

approximately

+130°C

the

output circuitry

enabled

again.

Depending

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.

Stable Range

Unstable Range

VIN=4.3V

CIN=COUT=1μF

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