STOD14

Application Information

Doc ID 023562 Rev 1

11/22

6

Application Information

6.1

Inductor selection

The inductor is the key passive component for switching converters.

For the step-down converter an inductance between 3.3 µH and 6.8 µH is recommended.

For the inverting stage the suggested inductance ranges from 3.3 µH to 4.7 µH.

It is very important to select a proper inductor according to the maximum current the

inductor can handle in order to avoid saturation. The peak current for the step-down and the

inverting can be calculated with the following formulas:

Equation 1

Equation 2

where

L1 is buck inductor value; including tolerance

L2 is inverter inductor value; including tolerance.

6.2

Input and output capacitor selection

It is recommended to use ceramic capacitors with low ESR as input and output capacitors in

order to filter any disturbance present in the input line and to get stable operation for the

switching converters.

6.3

Recommended PCB layout

The STOD14 is a high frequency power switching device so it requires a proper PCB layout

in order to obtain the necessary stability and optimize line/load regulation and output voltage

minimize the ground noise, a common ground node for power ground and a different one for

analog ground must be used. The exposed pad is connected to AGND through vias.

()

O

1

s

IN

1

O

1

O

BUCK

_

PEAK

I

L

f

2

V

/

V

1

V

I

+

⋅

⋅

−

⋅

=

()

()

IN

2

2

O

IN

O

IN

2

O

2

s

2

O

IN

INV

_

PEAK

V

V

V

I

V

V

L

f

2

V

V

I

⋅

η

−

+

−

⋅

⋅

⋅

=