LTC3531 Datasheet, PDF (11/16 Pages) Linear Technology – 200mA Buck-Boost Synchronous DC/DC Converters

LTC3531/
LTC3531-3.3/LTC3531-3
APPLICATIO S I FOR ATIO
Component Selection
Only three power components are required to
complete the design of the buck-boost converter, V_OUT
programming resistors are needed for the adjustable
version. The high operating frequency and low peak
currents of the LTC3531 allow the use of low value, low
profile inductors and tiny external ceramic capacitors.
Inductor Selection
For best efficiency, choose an inductor with high frequency
core material, such as ferrite, to reduce core loses. The
inductor should have low DCR (DC resistance) to reduce
the I²R losses, and must be able to handle the peak
inductor current without saturating. A 10μH to 22μH in-
ductor value with a >500mA current rating and <400mΩ
DCR is recommended. For applications where radiated
noise is a concern, a toroidal or shielded inductor can be
used. Table 2 contains a list of inductor manufacturers.
Capacitor Selection
The buck-boost convertor requires two capacitors. Ceramic
X5R types will minimize ESL and ESR while maintaining
capacitance at rated voltage over temperature. The V_IN
capacitor should be at least 2.2μF. The V_OUT capacitor
should be between 4.7μF and 22μF. A larger output capaci-
tor should be used if lower peak to peak output voltage
ripple is desired. A larger output capacitor will also improve
load regulation on V_OUT. See Table 3 for a list of capacitor
manufacturers for input and output capacitor selection.
Table 2. Inductor Vendor Information
Supplier
COEV
Coilcraft
Murata
Sumida
Toko
Series
DN4835
MSS4020
LPO3310
DS1608
LQH43CN
LQH32CN
CDRH4D18
CDRH3D16/HP
D312C
D412C
DB320C
Phone
[phone]
[phone]
Website
www.coev.net
www.coilcraft.com
USA: [phone] www.murata.com
[phone]
USA: [phone] www.sumida.com
Japan: 81-3-3607-5111
[phone]
www.tokoam.com
Table 3. Capacitor Vendor Information
Supplier
AVX
Murata
Sanyo
Taiyo Yuden
TDK
Series
X5R
X5R
POSCAP
X5R
X5R
Phone
Website
[phone]
www.avxcorp.com
USA: [phone] www.murata.com
[phone]
[phone]
www.sanyovideo.com
[phone]
www.taiyo-yuden.com
[phone]
www.component.tdk.com
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