STODD01

Application information

Doc ID 17789 Rev 2

21/31

9

Application information

9.1

Introduction

The following is some technical information for estimating the typical external components

characteristics using standard literature equations. Nevertheless, it is strongly

recommended to validate the external components suitability to the application

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

9.2

Programming the output voltage

The output voltage for the step-up (ch1) can be adjusted from 6.5 V up to 14 V by

divider must be connected to the FB1 pin, as shown in Figure 3.

The resistor divider should be chosen in accordance with the following equation:

Equation 1

It is recommended to use a resistor with a value in the range of 1 k

Ω to 50 kΩ. Lower values

can also be suitable, but increase current consumption.

For ch2 the device integrates the resistor divider needed to set the correct output voltage.

This allows 2 external components to be saved. The FB2 pin must be connected directly to

The output voltage for Ch3 can be adjusted from 0.8 V up to 85 % of the input voltage value

must be connected to FB3 pin, as shown in Figure 3.

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

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.

9.3

Inductor selection

The inductor is the key passive component for switching converters.

The inductor selection must take the boundary conditions in which the converter works into

consideration, the maximum input voltage for the buck and the minimum input voltage for the

boost.

⎟

⎠

⎞

⎜

⎝

⎛ +

×

=

2

R

1

R

1

V

V

1

FB

1

OUT

⎟

⎠

⎞

⎜

⎝

⎛ +

×

=

4

R

3

R

1

V

V

3

FB

3

OUT