15/19

AN458 APPLICATION NOTE

Diode: BYW98

Core: L = 40

µH Magnetics 58121-A2MPP 34 Turns 0.9mm (20AWG)

(*) Minimum 100

Figure 20. P.C. Board and Component Layout of the Circuit of fig. 21 (1:1 scale).

L4963 Step-Down Regulator Design Example

Referring to the complete typical application circuit shown in fig.19, and defined the following conditions:

s

s

s

s

s

We calculate the value of the external components.

1. OUTPUT VOLTAGE SETTING:

The output voltage is established by the voltage divider constituted by R5 and R6. To select the right R5 value

use the following formula:

where: Vref = 5.1V

R6 = Is normally set at 4K7

Ω

R5, R6

see table

Resistor Values for Standard Output Voltages

Vo

R6

R5

12

4.7K

Ω

6.2K

Ω

15

4.7K

Ω

9.1K

Ω

18

4.7K

Ω

12K

Ω

24

4.7K

Ω

18K

Ω

CAPACITORS

R5

V

ou t

V

ref

–

()

V

ref

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

R6

()

⋅

=