Application information component selection

AN2620

6/20

Doc ID 13883 Rev 3

The ST1S10 has been designed to have the best performances with ceramic capacitors. In

typical application conditions a minimum value of 22 µF ceramic capacitor is suggested on

the output, but higher values are suitable considering that the control loop has been

designed to properly work with a natural output LC frequency given by a 3.3 µH inductor and

It is advisable to use ceramic capacitors with a voltage rating in the range of 1.5 times the

maximum output voltage.

1.3

Inductor

The inductor value is very important because it fixes the ripple current flowing through the

Equation 7

2.8 µH. The peak current thought the inductor is given by:

Equation 8

It can be seen that if the inductor value decreases, the peak current (that has to be lower

than the current limit of the device) increases. So, for fixed the peak current, a higher value

of the inductor allows a higher value for the output current.

The ST1S10 is designed to have maximum performance with a 3.3 µH inductor value at

900 kHz.

The peak inductor current must be designed in order to not exceed the switching current

limit.

L

V

in

V

out

–

I

Δ

------------------------- T

on

⋅

=

I

PK

I

O

I

Δ

2

-----

+

=

I

SAT

I

PK

≥