AP6015

High Efficiency Step-Down Low Power DC-DC Converter

AP6015 Rev.

2

15 of 18

AUGUST 2008

www.diodes.com

Application Information

(Continued)

Input Capacitor Selection

Though there is no special requirement for the ESR (Equivalent Series Resistance) of the input capacitor, due

attention should be paid to the tolerance and temperature coefficient of the capacitor used.

A 10uF or larger

capacitance is required between the PVCC and the GND pins.

The input capacitor should be placed as

close as possible to the PVCC pin in order to achieve good overall system performance.

Output Capacitor Selection

Ripple at the voltage output pin is caused by the charge-and-discharge of the output capacitor.

For the best

performance, a low ESR output capacitor should be used.

The equation below demonstrates how the size of

the ripple can be calculated.

)

8

1

(

)

8

1

(

)

(

1

ESR

f

C

I

ESR

f

C

f

L

V

V

V

V

O

L

O

CC

O

O

O

+

×

×

×

Δ

=

+

×

×

×

×

−

×

=

Δ

Where:

△Vo= Output voltage ripple

L = Inductor value

f = Switching frequency (1MHz typical)