ACE738D datasheet(8/12 Pages) ACE

8 / 12 page

ACE738D

2A, 24V Synchronous Step-Down Converter

VER 1.1

Input Capacitor

The input capacitor is used to supply the AC input current to the step-down converter and maintaining the

DC input voltage. The ripple current through the input capacitor can be calculated by:

where ILOAD is the load current, VOUT is the output voltage, VIN is the input voltage.

Thus the input capacitor can be calculated by the following equation when the input ripple voltage is

determined.

where C1 is the input capacitance value, fs is the switching frequency,

△V

IN is the input ripple current.

The input capacitor can be electrolytic, tantalum or ceramic. To minimizing the potential noise, a small

X5R or X7R ceramic capacitor, i.e. 0.1uF, should be placed as close to the IC as possible when using

electrolytic capacitors.

A 10uF ceramic capacitor is recommended in typical application.

Output Capacitor

The output capacitor is required to maintain the DC output voltage, and the capacitance value determines

the output ripple voltage. The output voltage ripple can be calculated by:

where C2 is the output capacitance value and RESR is the equivalent series resistance value of the output

capacitor.

The output capacitor can be low ESR electrolytic, tantalum or ceramic, which lower ESR capacitors get

lower output ripple voltage.

The output capacitors also affect the system stability and transient response, and a 22uF ceramic

capacitor is recommended in typical application.

ACE738D Datasheet(PDF) 8 Page - ACE Technology Co., LTD.