LTC3670_15 Datasheet, PDF (9/12 Pages) Linear Technology – Monolithic 400mA Buck Regulator with Dual 150mA

LTC3670
APPLICATIONS INFORMATION
Buck Regulator Inductor Selection
Many different sizes and shapes of inductors are avail-
able from numerous manufacturers. Choosing the right
inductor from such a large selection of devices can be
overwhelming, but following a few basic guidelines will
make the selection process much simpler.
The buck regulator is designed to work with inductors in
the range of 2.2μH to 10μH. A 4.7μH inductor is a good
starting point. Larger value inductors reduce ripple cur-
rent which improves output ripple voltage. Lower value
inductors result in higher ripple current and improved
transient response time. To maximize efficiency, choose
an inductor with a low DC resistance. Choose an inductor
with a DC current rating at least 1.5 times larger than the
maximum load current to ensure that the inductor does not
saturate during normal operation. If output short-circuit
is a possible condition, the inductor should be rated to
handle the maximum peak current specified for the buck
regulator.
Different core materials and shapes will change the size/cur-
rent and price/current relationship of an inductor. Toroid
or shielded pot cores in ferrite or Permalloy materials
are small and do not radiate much energy, but generally
cost more than powdered iron core inductors with similar
electrical characteristics. Inductors that are very thin or
have a very small volume typically have much higher core
and DCR losses, and will not give the best efficiency. The
choice of which style inductor to use often depends more
on the price vs size, performance, and any radiated EMI
requirements than on what the buck regulator needs to
operate.
Table 1 shows several inductors that work well with the
buck regulator. These inductors offer a good compromise
in current rating, DCR and physical size. Consult each
manufacturer for detailed information on their entire
selection of inductors.
Table 1. Recommended Inductors for the Buck Regulator
L
INDUCTOR TYPE (μH)
MAXIMUM I_DC
(A)
MAXIMUM DCR
(Ω)
EPL2014-472ML 4.7
1.3
0.254
LPS3015
4.7
1.1
3.3
1.3
DE2818C
4.7
1.25
3.3
1.45
DE2812C
4.7
1.15
3.3
1.37
CDRH3D16
4.7
0.9
CDRH2D11
4.7
0.5
3.3
0.6
SD3118
4.7
1.3
3.3
1.59
0.2
0.13
0.072
0.053
0.13*
0.105*
0.11
0.17
0.123
0.162
0.113
*Typical DCR
SIZE in mm
(L × W × H)
1.8 × 2.0 × 1.4
3.0 × 3.0 × 1.5
3.0 × 3.0 × 1.5
3.0 × 2.8 × 1.8
3.0 × 2.8 × 1.8
3.0 × 2.8 × 1.2
3.0 × 2.8 × 1.2
4.0 × 4.0 × 1.8
3.2 × 3.2 × 1.2
3.2 × 3.2 × 1.2
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.8
MANUFACTURER
Coilcraft
www.coilcraft.com
Toko
www.toko.com
Sumida
www.sumida.com
Cooper
www.cooperet.com
3670f
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