LT1618EMS 데이터 시트보기 (PDF) - Linear Technology
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LT1618EMS Datasheet PDF : 16 Pages
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LT1618
APPLICATIONS INFORMATION
Inductor Selection
Several inductors that work well with the LT1618 are listed
in Table 1, although there are many other manufacturers
and devices that can be used. Consult each manufacturer
for more detailed information and for their entire selection
of related parts. Many different sizes and shapes are
available. Ferrite core inductors should be used to obtain
the best efficiency, as core losses at 1.4MHz are much
lower for ferrite cores than for the cheaper powdered-iron
ones. 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 mini-
mize I2R power losses. A 4.7µH or 10µH inductor will be
a good choice for many LT1618 designs.
Table 1. Recommended Inductors
PART
L MAX
(µH) (mΩ)
CDRH5D18-4R1 4.1
57
CDRH5D18-100 10
124
CR43-2R2
2.2
71
CR43-4R7
4.7 109
CR43-100
10
182
CR54-100
10
100
LQH3C1R0M24 1.0
78
LQH3C2R2M24 2.2 126
LQH3C4R7M24 4.7 260
HEIGHT
(mm)
2.0
2.0
3.5
3.5
3.5
4.8
2.0
2.0
2.0
VENDOR
Sumida
(847) 956-0666
www.sumida.com
Murata
(814) 237-1431
www.murata.com
Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used at the output to minimize the output ripple voltage.
Multilayer ceramic capacitors are an excellent choice.
They have an extremely low ESR and are available in very
small packages. X5R and X7R dielectrics are preferred, as
these materials retain their capacitance over wider voltage
and temperature ranges than other dielectrics. A 4.7µF to
10µF output capacitor is sufficient for high output current
designs. Converters with lower output currents may need
only a 1µF or 2.2µF output capacitor. Solid tantalum or
OSCON capacitors can be used, but they will occupy more
board area than a ceramic and will have a higher ESR for
the same footprint device. Always use a capacitor with a
sufficient voltage rating.
Ceramic capacitors also make a good choice for the input
decoupling capacitor, which should be placed as close as
possible to the VIN pin of the LT1618. A 1µF to 4.7µF input
capacitor is sufficient for most applications. Table 2 shows
a list of several ceramic capacitor manufacturers. Consult
the manufacturers for detailed information on their entire
selection of ceramic parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
VENDOR
PHONE
URL
Taiyo Yuden
(408) 573-4150 www.t-yuden.com
Murata
(814) 237-1431 www.murata.com
Kemet
(408) 986-0424 www.kemet.com
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast switching speed, are the ideal choice for LT1618
applications. Table 3 shows several Schottky diodes that
work well with the LT1618. Many different manufacturers
make equivalent parts, but make sure that the component
chosen has a sufficient current rating and a voltage rating
greater than the output voltage. The diode conducts cur-
rent only when the power switch is turned off (typically
less than half the time), so a 0.5A or 1A diode will be
sufficient for most designs. The companies below also
offer Schottky diodes with higher voltage and current
ratings.
Table 3. Recommended Schottky Diodes
1A PART 0.5A PART VENDOR
PHONE/URL
UPS120
UPS130
UPS140
Microsemi
(510) 353-0822
www.microsemi.com
MBRM120 MBR0520
MBRM130 MBR0530
MBRM140 MBR0540
ON Semiconductor (800) 282-9855
www.onsemi.com
B120
B0520
B130
B0530
B140
B0540
Diodes, Inc
(805) 446-4800
www.diodes.com
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