Datasheet

LT3598
10
3598fb
Inductor Selection
Table 1 lists several inductors that work well with the
LT3598, however, there are many other manufacturers and
devices that can be used. Consult each manufacturer for
detailed information on their entire range of parts. Ferrite
core inductors should be used to obtain the best effi ciency.
Choose an inductor that can handle the necessary peak
current without saturating. Also, ensure that the inductor
has a low DCR (copper wire resistance) to minimize I
2
R
power losses. Values between 4.7μH and 22μH will suffi ce
for most applications.
Inductor manufacturers specify the maximum current
rating as the current where inductance falls by a given
percentage of its nominal value. An inductor can pass a
current greater than its rated value without damaging it.
Consult each manufacturer to determine how the maximum
inductor current is measured and how much more current
the inductor can reliably conduct.
Table 1. Recommended Inductors
PART
L
(μH)
MAX
DCR
(Ω)
CURRENT
RATING
(A) VENDOR
B1015AS-100M
#817FY-4R7M
1123AS-4R7M
10
4.7
4.7
0.07
0.06
0.12
2.2
2.26
1.90
TOKO
www.toko.com
74454068
74454010
7447745100
6.8
10
10
0.055
0.065
0.12
2.2
2
1.7
Würth Electronics
www.we-online.com
CDH74NP-120L
CDH74NP-150L
CDRH6D38-100
12
15
10
0.065
0.083
0.038
2.45
2.10
2.00
Sumida
www.sumida.com
IHLP-2525BD-01 10 0.129 2.5 Vishay
www.vishay.com
SD25-4R7-R 4.7 0.056 1.83 Cooper
www.cooperet.com
LPS4018-472ML 4.7 0.200 1.8 Coilcraft
www.coilcraft.com
Capacitor Selection
Low ESR (equivalent series resistance) ceramic capacitors
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
APPLICATIONS INFORMATION
temperature ranges than other dielectrics. A 4.7μF to 10μF
output capacitor is suffi cient for most high output current
designs. Table 2 lists some suggested manufacturers.
Consult the manufacturers for detailed information on
their entire selection of ceramic parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden 408-573-4150
www.t-yuden.com
AVX 843-448-9411
www.avxcorp.com
Murata 770-436-1300
www.murata.com
Kemet 408-986-0424
www.kemet.com
United Chemi-Con 847-696-2000
www.chemi-con.com
Diode Selection
Schottky diodes, with their low forward voltage drop
and fast switching speed, must be used for all LT3598
applications. Do not use P-N diodes. Table 3 lists several
Schottky diodes that work well. The diode’s average current
rating must exceed the application’s average output current.
The diode’s maximum reverse voltage must exceed the
application’s output voltage. A 2A diode is suffi cient for
most designs. For PWM dimming applications, be aware
of the reverse leakage current of the diode. Lower leakage
current will drain the output capacitor less, allowing for
higher dimming range. The companies below offer Schottky
diodes with high voltage and current ratings.
Table 3. Suggested Diodes
PART
MAX
CURRENT
(A)
MAX REVERSE
VOLTAGE
(V) MANUFACTURER
B250A
B240A
SBR140S3
SBM340, PDS340
2
2
1
3
50
40
40
40
Diodes, Inc.
www.diodes.com
HSM150G
HSM150J
1
1
50
50
Microsemi
www.microsemi.com
SS3H9 3 90 Vishay
www.vishay.com