5/11

Axelite Confidential Materials, do not copy or distribute without written consent.

Rev.1.5 Nov.06, 2019

AX5201

Table 1 Resistor select for output voltage setting

VOUT

R3

R4

12V

1K

11K

15V

1.3K

18K

18V

1.3K

22K

24V

1.3K

30K

32V

2.2K

68K

Inductor Selection

For most designs, Low inductance values are physically smaller but require faster

switching, which results in some efficiency loss. The inductor value can be derived from the

following equation:





f

I

V

V

V

V

L

LX

L

OUT

IN

OUT

IN













Where is inductor Ripple Current. Large value inductors lower ripple current and small

value inductors result in high ripple currents. Choose inductor ripple current approximately

15% of the maximum input current 2.4A, ΔIL=0.18A.

Table 2 Inductor select for output voltage setting (VCC=5V)

VOUT

9V

12V

15V

18V

L1 Value

18uH

22uH

25uH

33uH

The DC current rating of the inductor should be at least equal to the maximum load

current plus half the ripple current to prevent core saturation (2.4A+0.18A).

Input Capacitor Selection

The input capacitor reduces the surge current drawn from the input and switching

noise from the device. The input capacitor impedance at the switching frequency shall be

less than input source impedance to prevent high frequency switching current passing to

the input. A low ESR input capacitor sized for maximum RMS current must be used.

The capacitor voltage rating should be at least 1.5 times greater than the input

voltage, and often much higher voltage ratings are needed to satisfy.