LSP5523

Document number: DS44073 Rev. 7 - 2

7 of 17

www.diodes.com

May 2022

© 2022 Copyright Diodes Incorporated. All Rights Reserved.

LSP5523

Output Voltage Setting

FB

R1

R2

V

O U T

Figure1. Output Voltage Setting

Figure 1 shows the connections for setting the output voltage. Select the proper ratio of the two feedback

resistors R1 and R2 based on the output voltage. Typically, use R2 ≈ 10KΩ and determine R1 from the

following equation:

Table1－ Recommended Resistance Values

Inductor Selection

The inductor maintains a continuous current to the output load. This inductor current has a ripple that is

dependent on the inductance value: higher inductance reduces the peak-to-peak ripple current. The trade off

for high inductance value is the increase in inductor core size and series resistance, and the reduction in

current handling capability. In general, select an inductance value L based on the ripple current requirement:

R I P P L E

O U T M A X

SW

IN

O U T

IN

O U T

K

I

f

V

)

V

V

(

V

L







where VIN is the input voltage, VOUT is the output voltage, fSW is the switching frequency, IOUTMAX is the maximum

output current, and KRIPPLE is the ripple factor. Typically, choose KRIPPLE = ~ 30% to correspond to the peak-to-

peak ripple current being ~30% of the maximum output current.

With this inductor value, the peak inductor current is IOUT • (1 + KRIPPLE / 2). Make sure that this peak inductor

current is less than the upper switch current limit. Finally, select the inductor core size so that it does not

saturate at the current limit. Typical inductor values for various output voltages are shown in Table 2.

VOUT

1.0V 1.2V 1.5V 1.8V 2.5V 3.3V

5V

9V

L

4.7uH 4.7uH 10uH 10uH 10uH 10uH 10uH 22uH

Table 2. Typical Inductor Values

VOUT

R1

R2

1.0V

1.0 KΩ

12 KΩ

1.2V

3.0 KΩ

10 KΩ

1.8V

9.53 KΩ

10 KΩ

2.5V

16.9 KΩ

10 KΩ

3.3V

26.1 KΩ

10 KΩ

5V

44.2 KΩ

10 KΩ

12V

121 KΩ

10 KΩ

(1)

(2)