Application information

ST1S41

16/27

DocID023654 Rev 2

In Table 6 some multi-layer ceramic capacitors suitable for this device are reported.

A ceramic bypass capacitor, as close as possible to the VINA pin, so that additional parasitic

ESR and ESL are minimized, is suggested in order to prevent instability on the output

voltage due to noise. The value of the bypass capacitor can go from 330 nF to 1 uF.

6.2

Inductor selection

The inductance value fixes the current ripple flowing through the output capacitor. So the

minimum inductance value to have the expected current ripple must be selected. The rule to

fix the current ripple value is to have a ripple at 20%-40% of the output current.

In continuous current mode (CCM), the inductance value can be calculated by the following

equation:

Equation 19

calculate minimum duty). So, fixing

minimum inductance value can be calculated as:

Equation 20

The peak current through the inductor is given by:

Equation 21

Table 6. Input MLCC capacitors

Manufacturer

Series

Cap value (

μF)

Rated voltage (V)

Murata

GRM31

10

25

GRM55

10

25

TDK

C3225

10

25

ΔI

L

V

IN

V

OUT

–

L

------------------------------

T

ON

⋅

V

OUT

L

--------------

T

OFF

⋅

==

L

MIN

V

OUT

ΔI

MAX

----------------

1D

MIN

–

F

SWMIN

-----------------------

⋅

=

I

LPK

,

I

O

ΔI

L

2

--------

+

=