LTC3528_15 Datasheet, PDF (12/18 Pages) Linear Technology – 1A, 1MHz Synchronous Step-Up DC/DC Converters

LTC3528/LTC3528B
APPLICATIONS INFORMATION
The inductor current ripple is typically set for 20% to
40% of the maximum inductor current. High frequency
ferrite core inductor materials reduce frequency depen-
dent power losses compared to cheaper powdered iron
types, improving efficiency. The inductor should have low
ESR (series resistance of the windings) to reduce the I²R
power losses, and must be able to handle the peak induc-
tor current without saturating. Molded chokes and some
chip inductors usually do not have enough core area to
support the peak inductor currents of 1.5A seen on the
LTC3528/LTC3528B. To minimize radiated noise, use a
shielded inductor. See Table 1 for suggested components
and suppliers.
Table 1. Recommended Inductors
VENDOR
PART/STYLE
Coilcraft
[phone]
www.coilcraft.com
LPO2506, MSS5131
MSS6122, MOS6020
ME3220, DO1608C
1812PS
Coiltronics
SD14, SD18, SD20
SD25, SD52
Sumida
[phone]
www.sumida.com
CD43
CDC5D23B
CDRH5D18
CR43
TDK
VLP, VLF
VLCF, SLF
Toko
[phone]
www.tokoam.com
D53, D63
D73, D75
Wurth
[phone]
www.we-online.com
WE-TPC type M, MH
Output and Input Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used to minimize the output voltage ripple. Multilayer
ceramic capacitors are an excellent choice as they have
extremely low ESR and are available in small footprints.
A 10µF to 22µF output capacitor is sufficient for most ap-
plications. Values larger than 22µF may be used to obtain
extremely low output voltage ripple and improve transient
response. X5R and X7R dielectric materials are preferred
for their ability to maintain capacitance over wide voltage
and temperature ranges. Y5V types should not be used.
The internal loop compensation of the LTC3528/LTC3528B
is designed to be stable with output capacitor values of
10µF or greater. Although ceramic capacitors are recom-
mended, low ESR tantalum capacitors may be used as well.
A small ceramic capacitor in parallel with a larger tantalum
capacitor may be used in demanding applications which
have large load transients. Another method of improving the
transient response is to add a small feed-forward capaci-
tor across the top resistor of the feedback divider (from
V_OUT to FB). A typical value of 33pF will generally suffice.
Low ESR input capacitors reduce input switching noise
and reduce the peak current drawn from the battery. It
follows that ceramic capacitors are also a good choice
for input decoupling and should be located as close as
possible to the device. A 10µF input capacitor is sufficient
for most applications. Larger values may be used without
limitations. Table 2 shows a list of several ceramic capaci-
tor manufacturers. Consult the manufacturers directly for
detailed information on their selection of ceramic parts.
Table 2. Capacitor Vendor Information
SUPPLIER
PHONE
WEBSITE
AVX
[phone] www.avxcorp.com
Murata
[phone] www.murata.com
Taiyo-Yuden
[phone] www.t-yuden.com
TDK
[phone] www.component.tdk.com
3528fd
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