Datasheet

LTC3531/
LTC3531-3.3/LTC3531-3
11
3531fa
S I FOR ATIOAPPLICATIO
WUU
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Table 3. Capacitor Vendor Information
Supplier Series Phone Website
AVX X5R [phone] www.avxcorp.com
Murata X5R USA: [phone] www.murata.com
[phone]
Sanyo POSCAP [phone] www.sanyovideo.com
Taiyo Yuden X5R [phone] www.taiyo-yuden.com
TDK X5R [phone] www.component.tdk.com
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
profi le inductors and tiny external ceramic capacitors.
Inductor Selection
For best effi ciency, 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 I
2
R 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 Series Phone Website
COEV DN4835 [phone] www.coev.net
Coilcraft MSS4020 [phone] www.coilcraft.com
LPO3310
DS1608
Murata LQH43CN USA: [phone] www.murata.com
LQH32CN [phone]
Sumida CDRH4D18 USA: [phone] www.sumida.com
CDRH3D16/HP Japan: 81-3-3607-5111
Toko D312C [phone] www.tokoam.com
D412C
DB320C