ACE725E

24V , 1.2A

High Efficiency Step-Down Converter

VER 1.1

9

Output Capacitor Selection

For

most applications a nominal 22μF or larger capacitor is suitable.

The ACE725E internal compensation is designed for a fixed corner frequency that is equal to

1

C

The output capacitor keeps output ripple small and ensures control-loop stability. The output capacitor

must also have low impedance at the switching frequency. Ceramic, polymer, and tantalum capacitors are

suitable, with ceramic exhibiting the lowest ESR and

high-frequency impedance. Output ripple with a

ceramic output capacitor is approximately as follows:

If the capacitor has significant ESR, the output ripple component due to capacitor ESR is as follows:

Input Capacitor Selection

The input capacitor in a DC-to-DC converter reduces current peaks drawn from the battery or other

input power source and reduces switching noise in the controller. The impedance of the input capacitor at

the switching frequency should be less than that of the input source so high-frequency switching currents

do not pass through the input source. The output capacitor keeps output ripple small and ensures

control-loop stability.

Components Selection

L (μH)

8

22x2

10 to 15

5

22x2

6.8 to 10

3.3

22x2

4.7 to 10

2.5

22x2

3.3 to 10

FC=

2