AP7115

150mA LOW DROPOUT LINEAR REGULATOR WITH

SHUTDOWN

AP7115 Rev. 10

8 of 11

MAY 2009

www.diodes.com

Application Note

Input Capacitor

An 1uF input capacitor is required between the AP7115 input pin

and GND.

There are no requirements for the ESR on input capacitor, but

tolerance and temperature coefficient must be considered.

Output Capacitor

The AP7115 can work with very small ceramic output capacitors

(1uF or greater). Higher capacitance values help to improve

transient. The output capacitor’s ESR is critical because it from a

zero to provide phase lead which is required for loop stability.

Figure below is Cout ESR vs. Load Current.

Band-Gap Bypass Capacitor

0.1uF bypass capacitor Between BP pin and GND can reduces

output voltage noise.

Shutdown Input Operation

The AP7115 is shutdown by pulling the EN pin low, and turned on

by driving the input high. If the shutdown feature is not required,

the EN pin should be tied to VIN to keep the regulator on at all

times.

Dropout Voltage

Current Limit

The AP7115 monitors and controls the PMOS’ gate voltage,

limiting the output current to 250mA(typ.). The output can be

shorted to ground for an indefinite period of time without

damaging the part.

PCB Layout

Optimum performance can only be achieved when the device is

mounted on a PC board according to the diagram below:

Thermal Considerations

Thermal Shutdown Protection limits power dissipation in AP7115.

When the operation junction temperature exceeds 155°C, the

Over Temperature Protection circuit starts the thermal shutdown

function and turns the pass element off. The pass element turn

on again after the junction temperature cools by 30°C. For

continuous

operation,

do

not

exceed

absolute

maximum

operation junction temperature 125°C. The power dissipation

definition in device is:

The maximum power dissipation depends on the thermal

resistance of IC package, PCB layout, the rate of surroundings

airflow and temperature difference between junction to ambient.

The maximum power dissipation can be calculated by the

following formula:

to ambient thermal resistance.

AP7115 Region of Stable Cout ESR vs.

Load Current

0.01

0.1

1

10

100

0

20

40

60

80

100

120

140

160

Load Current (mA)

Stable