Application information

STOD03B

12/22

Doc ID 022613 Rev 1

7

Application information

7.1

External passive components

7.1.1

Inductor selection

Magnetic shielded low ESR power inductors must be chosen as the key passive

components for switching converters.

For the step-up converter an inductance between 4.7 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 the right inductor according to the maximum current the

inductor can handle to avoid saturation. The step-up and the inverting peak current can be

calculated as follows:

Equation 1

Equation 2

where

value);

η1: efficiency of step-up converter. Typical value is 0.70;

η2: efficiency of inverting converter. Typical value is 0.60.

current, at the maximum load condition, increases. A proper inductor, with a saturation

current as a minimum of 1 A, is preferred.

STOD03B is capable of supplying a load current from 150 mA to 200 mA. Inductors with a

saturation current as a minimum of 1 A must be selected.

1

L

fs

V

2

)

VIN

V

(

VIN

VIN

1

I

V

I

MID

MIN

MID

MIN

MIN

OUT

MID

BOOST

PEAK

×

×

×

−

×

+

×

η

×

=

−

2

L

fs

)

VIN

2

VO

(

2

2

VO

VIN

VIN

2

xI

)

2

VO

VIN

(

I

MIN

MIN

MIN

MIN

MIN

OUT

MIN

MIN

INVERTING

PEAK

×

×

−

×

×

+

×

η

−

=

−