ltc3586 Linear Technology Corporation, ltc3586 Datasheet - Page 29

• Manufacturer Part Number: ltc3586
• Description: High Ef? Ciency Usb Power Manager With Boost, Buck-boost And Dual Bucks
• Manufacturer: Linear Technology Corporation

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 converters.
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 don’t 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 LTC3586 requires to operate.
The inductor value also has an effect on Burst Mode
operations. Lower inductor values will cause the Burst
Mode switching frequencies to increase.
Table 5 shows several inductors that work well with the
LTC3586’s buck regulators. 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.
APPLICATIONS INFORMATION
Table 5. Recommended Inductors for Buck Regulators
INDUCTOR
TYPE
DE2818C
DE2812C
CDRH3D16 4.7
SD3118
SD3112
LPS3015
*Typical DCR
(μH)
4.7 1.25 0.072* 3.0 × 2.8 × 1.8 Toko
4.7
4.7
4.7
4.7
L
MAX
1.15 0.13* 3.0 × 2.8 × 1.2
I
(A)
0.9
1.3
0.8
1.1
DC
0.162 3.1 × 3.1 × 1.8 Cooper
0.246 3.1 × 3.1 × 1.2
MAX
DCR
0.11
(Ω)
0.2
3.0 × 3.0 × 1.5 Coilcraft
SIZE IN mm
(L × W × H)
4 × 4 × 1.8
MANUFACTURER
www.toko.com
Sumida
www.sumida.com
www.cooperet.com
www.coilcraft.com
Table 6. Recommended Ceramic Capacitor Manufacturers
AVX
Murata
Taiyo Yuden
Vishay Siliconix
TDK
BUCK-BOOST REGULATOR APPLICATIONS SECTION
Buck-Boost Regulator Inductor Selection
Inductor selection criteria for the buck-boost are similar
to those given for the buck switching regulator. The buck-
boost converter is designed to work with inductors in the
range of 1μH to 5μH. For most applications a 2.2μH inductor
will suffi ce. Choose an inductor with a DC current rating
at least 2 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 specifi ed for the buck-boost converter.
Table 7 shows several inductors that work well with the
LTC3586’s buck-boost 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.
Buck Regulator Input/Output Capacitor Selection
Low ESR (equivalent series resistance) MLCC capacitors
should be used at both buck regulator outputs as well as at
each buck regulator input supply (V
or X7R ceramic capacitors should be used because they
retain their capacitance over wider voltage and temperature
ranges than other ceramic types. A 10μF output capaci-
tor is sufficient for most applications. For good transient
response and stability the output capacitor should retain
at least 4μF of capacitance over operating temperature
and bias voltage. Each buck regulator input supply should
be bypassed with a 1μF capacitor. Consult with capacitor
manufacturers for detailed information on their selection
and specifications of ceramic capacitors. Many manufac-
turers now offer very thin (<1mm tall) ceramic capacitors
ideal for use in height-restricted designs. Table 6 shows a
list of several ceramic capacitor manufacturers.
www/avxcorp.com
www.murata.com
www.t-yuden.com
www.vishay.com
www.tdk.com
IN1
and V
LTC3586
IN2
). Only X5R
29
3586f