exhibiting the lowest ESR and high-frequency impedance. Output ripple with a ceramic output capacitor is approximately

as follows:VRIPPLE = IL(PEAK)[1 / (2π x fOSC x COUT)]

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

VRIPPLE(ESR) = IL(PEAK) x ESR

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

VOUT (V)

COUT (μF)

L (μH)

8

22

15 to 22

5

22

10 to 15

3.3

22

6.8 to 10

LESHAN RADIO COMPANY, LTD.

7/8