ST2S08B

Application information

Doc ID 18290 Rev 2

11/18

8

Application information

8.1

Introduction

The following technical information is used for estimating typical external component

characteristics using standard equations. Nevertheless, it is strongly recommended to

validate the suitability of external components to the application requirements by thoroughly

testing any solution at bench level on a real evaluation circuit.

8.2

Programming the output voltage

The output voltage for both channels can be adjusted from 0.8 V up to 85 % of the input

divider must be connected to the feedback (FB) pin, as shown in

Figure 3.

The resistor divider must be chosen according to the following equations:

Equation 1

Equation 2

Using a resistor with a value in the range of 1 k

Ω to 50 kΩ is recommended. Lower values

are also suitable, but increase current consumption.

8.3

Inductor selection

The inductor is the key passive component for switching converters.

The critical inductance values can then be obtained according to the following formulas:

Equation 3

can be set at 20 % - 40 % of the output current.

The peak current of the inductor can be calculated as:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

×

=

2

R

1

R

1

V

V

1

FB

1

O

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

×

=

4

R

3

R

1

V

V

2

FB

2

O

L

SW

MAX

_

IN

O

MAX

_

IN

O

MIN

I

F

V

)

V

V

(

V

L

Δ

×

×

−

×

=