AP7165

600mA LOW DROPOUT REGULATOR WITH POK

AP7165 Rev. 1

9 of 11

OCTOBER 2007

www.diodes.com

Application Note

Input Capacitor

A 1

μF ceramic capacitor is recommended to connect

between IN and GND pins to decouple input power

supply glitch and noise. The amount of the capacitance

may be increased without limit. A lower ESR (Equivalent

Series Resistance) capacitor allows the use of less

capacitance, while higher ESR type requires more

capacitance. This input capacitor should be located as

close as possible to the device to assure input stability

and less noise. For PCB layout, a wide copper trace is

required for both IN and GND.

Output Capacitor

The output capacitor is required to stabilize and help the

transient response of the LDO. The AP7165 is designed

to

have

excellent

transient

response

for

most

applications with a small amount of output capacitance.

The AP7165 is stable for all available types and values

of output capacitors

≥ 4.7μF. The device is also stable

with multiple capacitors in parallel, which can be of any

type of value. Additional capacitance helps to reduce

undershoot

and

overshoot

during

transient.

This

capacitor should be placed as close as possible to OUT

and GND pins for optimum performance.

Adjustable Operation

The AP7165 provides output voltage from 0.8V to 5.0V

through external resistor divider as shown below.

IN

GND

EN

OUT

Enable

FB

POK

100kOhm

AP7165

The output voltage is calculated by:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

=

2

1

REF

OUT

R

R

1

V

V

Rearranging

the equation will give the following

equation to find the approximate resistor divider values:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

=

1

V

V

R

R

REF

OUT

2

1

To maintain the stability of the internal reference voltage,

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 AP7165 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

950mA (600A 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

380mA.

This

feature

protects

the

regulator

from

over-current

and

damage

due

to

overheating.