SC187

Output L-C filter Selection

SC187 has fixed internal loop-gain compensation. It is

optimized for X5R or X7R ceramic output capacitors and

an output L-C filter corner frequency of less than 34kHz.

The output L-C corner frequency can be determined by

Equation 2.

OUT

C

C

L

2

1

f

In general, the inductor is chosen to set the inductor ripple

current to approximately 30% of the maximum output

current. It is recommended to use a typical inductor value

of 1μH to 2.2μH with output ceramic capacitors of 44μF or

higher capacitance. Lower inductance should be consid-

ered in applications where faster transient response is

required. More output capacitance will reduce the output

deviation for a particular load transient. When using low

inductance, the maximum peak inductor current at any

condition (normal operation and start up) can not exceed

5A which is the guaranteed minimum current limit. The

saturation current rating of the inductor needs to be at

least larger than the peak inductor current which is the

maximum output current plus half of inductor ripple

current.

Applications Information (continued)

14