EP3003

Input Capacitor Selection

The input capacitor reduces the surge current drawn from the input and switching noise from the device.

The input capacitor impedance at the switching frequency shall be less than input source impedance to

prevent high frequency switching current passing to the input. A low ESR input capacitor sized for

maximum RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly

recommended because of their low ESR and small temperature coefficients. A 10µF ceramic capacitor

for most applications is sufficient.

Output Capacitor Selection

The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop

stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors

with X5R or X7R dielectrics are recommended due to their low ESR and minimization of large

temperature and voltage coefficients. The output ripple

OUT

V

∆

is determined by:

()

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

×

×

+

×

×

×

−

×

≤

∆

3

8

1

C

f

ESR

L

f

V

V

V

V

V

OSC

OSC

IN

OUT

IN

OUT

OUT

Rev.03

11