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APW7071CE-TU

White LED DC/DC Step-Up Converter

Anpec Electronics 

APW7071

Application Information (Cont.)

Inductor selection

Since the PFM peak current control scheme is

inherently stable, the inductor value does not affect

the stability of the regulator. The selection of the

inductor together with the nominal load current,

internal set peak current, input and output voltage of

the application determines the switching frequency

of the converter. For the LED application, inductor

values between 2.2 µH up to 10 µH are

recommended.

Recommended inductors

Part No.

Value(µH) Vendor

LQH32CN4R7M23L 4.7

Murata

LQH32CN100K53L 10

Murata

SH30184R7YSB

4.7

SH3018100YSB

10

ABC

ABC

Output capacitor selection

For better output voltage filtering, a low ESR output

capacitor is recommended. Ceramic capacitors have

a low ESR value, but depending on the application,

tantalum capacitors can be used. The selection of the

output capacitor value directly influences the output

voltage ripple of the converter which also influences

line regulation. The larger the output voltage ripple,

the larger the line regulation, which means that the

LED current changes if the input voltage changes. If a

certain change in LED current gives a noticeable

change in LED brightness, depends on the LED manu-

facturer and on the application. Applications requiring

good line regulation ±1%/V (typ) must use output ca-

pacitor values eqµAl or large than 1 µF.

Recommended output capacitor

Part No.

Value

Vender

GRM185R61C105KE44D 1.0µF/X5R/ Murata

0603/16V

Any

0.22µF Any

Any

0.1µF

Any

Input capacitor selection

For good input voltage filtering, low ESR ceramic ca-

pacitors are recommended. A 4.7µF ceramic input

capacitor is sufficient for most applications. For bet-

ter input voltage filtering the capacitor value can be

increased.

Recommended input capacitor

Part No.

Value

Vender

GRM188R60J475KE19D 4.7µF/X5R/ Murata

0603/6.3V

GRM219R60J106KE19D 10µF/X5R/ Murata

0805/6.3V

Diode selection

To achieve high efficiency a Schottky diode must be

used. The current rating of the diode must meet the

peak current rating of the converter.

Recommended diode

Part No.

MSCD052

Reverse

Voltage

20

Vender

Zowie

Layout considerations

Typical for all switching power supplies, the layout is

an important step in the design; especially at high

peak currents and switching frequencies. If the layout

is not carefully done, the regulator might show noise

problems and duty cycle jitter. The input capacitor

should be placed as close as possible to the input pin

for good input voltage filtering. The inductor and diode

should be placed as close as possible to the switch

Copyright © ANPEC Electronics Corp.

10

Rev. A.1 - Feb., 2006

www.anpec.com.tw

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