LT3489 Ver la hoja de datos (PDF) - Linear Technology
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LT3489 Datasheet PDF : 12 Pages
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LT3489
APPLICATIO S I FOR ATIO
Inductor Selection
Several inductors that work well with the LT3489 are listed
in Table 1. This table is not exclusive; there are many other
manufacturers and inductors that can be used. Consult
each manufacturer for more detailed information and for
their entire selection of related parts, as many different
sizes and shapes are available. Ferrite core inductors
should be used to obtain the best efficiency, as core
losses at 2MHz are much lower for ferrite cores than for
the cheaper powdered-iron ones. Choose an inductor that
can handle at least 2.5A without saturating, and ensure
that the inductor has a low DCR (copper wire resistance)
to minimize I2R power losses. A 2.2μH to 5μH inductor
will be the best choice for most LT3489 designs. Note
that in some applications, the current handling require-
ments of the inductor can be lower, such as in the SEPIC
topology where each inductor only carries one-half of the
total switch current. The inductors shown in Table 1 were
chosen for small size. For better efficiency, use similar
valued inductors with a larger volume.
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, as
they have an extremely low ESR and are available in very
small packages. X5R or X7R dielectrics are preferred, as
these materials retain the capacitance over wide voltage
and temperature ranges. A 4.7µF to 20µF output capacitor
is sufficient for most applications, but systems with very
low output currents may need only a 1µF or 2.2µF output
capacitor. Solid tantalum or OS-CON capacitors can be
used, but they will occupy more board area than a ceramic
and will have a higher ESR. 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 LT3489. A 2.2μF 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 1. Recommended Inductors
PART
SD25-2R2
SD25-3R3
SD25-4R7
A916CY-2R7M
A916CY-3R3M
A916CY-4R7M
LQH55DN2R2M03
LQH55DN3R3M03
LQH55DN4R7M03
L (μH)
2.2
3.3
4.7
2.7
3.3
4.7
2.2
3.3
4.7
TYPICAL DCR (mΩ)
31
38
47
18.3
21.4
26.3
29
36
41
SIZE
L × W × H (mm)
5.45 × 5.45 × 2.7
6 × 6 × 3.5
5.7 × 5 × 4.7
VENDOR
CooperBussmann
(888) 414-2645
www.cooperet.com
Toko
www.toko.com
Murata
(770) 436-1300
www.murata.com
Table 2. 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
3489f
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