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LT3477

3477fc

APPLICATIONS INFORMATION

Capacitor Selection

Low ESR (equivalent series resistance) ceramic capaci-

tors should be used at the output to minimize the output

ripple voltage. Use only X5R or X7R dielectrics, as these

materials retain their capacitance over wider voltage and

temperature ranges better than other dielectrics. A 4.7μF

to 10μF output capacitor is sufﬁcient for most high output

current designs. Converters with lower output currents

may need only a 1μF or 2.2μF output capacitor.

Table 1. Ceramic Capacitor Manufacturers

MANUFACTURER

PHONE

WEB

Taiyo Yuden

(408) 573-4150

www.t-yuden.com

AVX

(803) 448-9411

www.avxcorp.com

Murata

(714) 852-2001

www.murata.com

TDK

(847) 803-6100

www.component.tdk.com

Inductor Selection

Several inductors that work well with the LT3477 are listed

in Table 2. However, there are many other manufacturers

and devices that can be used. Consult each manufacturer

for more detailed information and their entire range of

parts. Ferrite core inductors should be used to obtain the

best efﬁciency. Choose an inductor that can handle the

necessary peak current without saturating, and ensure

that the inductor has a low DCR (copper-wire resistance)

to minimize I2R power losses. A 4.7μH or 10μH inductor

will sufﬁce for most LT3477 applications.

Inductor manufacturers specify the maximum current

rating as the current where the inductance falls to some

percentage of its nominal value—typically 65%. An

inductor can pass a current larger than its rated value

without damaging it. Aggressive designs where board

space is precious will exceed the maximum current rat-

ing of the inductor to save board space. Consult each

manufacturer to determine how the maximum inductor

current is measured and how much more current the

inductor can reliably conduct.

Diode Selection

Schottky diodes, with their low forward voltage drop and

fast switching speed, are ideal for LT3477 applications.

Table 3 lists several Schottky diodes that work well with

the LT3477. The diode’s average current rating must exceed

the average output current. The diode’s maximum reverse

voltage must exceed the output voltage. The diode conducts

current only when the power switch is turned off (typically

less than 50% duty cycle), so a 3A diode is sufﬁcient for

most designs. The companies below also offer Schottky

diodes with higher voltage and current ratings.

Table 3. Suggested Diodes

MANUFACTURER

PART NUMBER

MAX

CURRENT (A)

MAX REVERSE

VOLTAGE (V)

MANUFACTURER

UPS340

UPS315

Microsemi

www.microsemi.com

B220

B230

B240

B320

B330

B340

SBM340

Diodes, Inc

www.diodes.com

Table 2. Suggested Inductors

MANUFACTURER

PART NUMBER

IDC

(A)

INDUCTANCE

(μH)

MAX DCR

(mΩ)

× W × H

(mm)

MANUFACTURER

CDRH6D283R0

CDRH6D28100

CDRH4D284R7

1.7

1.32

4.7

6.7

× 6.7 × 3.0

6.7

× 6.7 × 3.0

5.0

× 5.0 × 3.0

Sumida

www.sumida.com

LM N 05D B4R7M

LM N 05D B100K

2.2

1.6

4.7

5.9

× 6.1 × 2.8

5.9

× 6.1 × 2.8

Taiyo Yuden

www.t-yuden.com

LQH55DN4R7M01L

LQH55DN100M01K

2.7

1.7

4.7

130

5.7

× 5.0 × 4.7

5.7

× 5.0 × 4.7

Murata

www.murata.com

FDV0630-4R7M

4.2

4.7

7.0

× 7.7 × 3.0

Toko

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