Datasheet

LTC3525-3/
LTC3525-3.3/LTC3525-5
10
3525fb
Component Selection
Inductor values between 4.7µH and 15µH are recom-
mended. In most applications 10µH will yield the best
compromise between size and efficiency. The inductor
should be a low loss ferrite design and must be rated for
peak currents of at least 400mA without saturating. Induc-
tors with lower DC resistance will improve efficiency. Note
that the inductor value does not have a significant effect
on ripple current, so while lower values will increase the
operating frequency, they do not reduce output voltage
ripple.
Some recommended inductor examples are Murata
LQH32C and Coilcraft LPO4812, LPO3310, DO3314,
DS1608 and MSS4020.
A ceramic input bypass capacitor should be located as
close as possible to the V
IN
and GND pins of the IC. A
minimum value of 1µF is recommended. If the battery is
more than a few inches away, a bulk tantalum decoupling
cap of at least 10µF is recommended on V
IN
.
The output capacitor should also be a ceramic, located close
to the V
OUT
and GND pins. A minimum value of 10µF is
recommended. Increasing the value of the output capacitor
to 22µF will result in lower output ripple. Higher capacitor
values will only offer a small reduction in output ripple,
while reducing light load efficiency by causing the peak
inductor current to increase above its minimum value of
150mA. The input and output capacitors should be X5R
or X7R types, not Y5V.
Figure 3. Recommended Component Placement
Table 1. Inductor Vendor Information
SUPPLIER PHONE FAX WEBSITE
Murata USA: [phone] USA: [phone] www.murata.com
Coilcraft [phone] [phone] www.coilcraft.com
Sumida USA: [phone] USA: [phone] www.sumida.com
Table 2. Capacitor Vendor Information
SUPPLIER PHONE FAX WEBSITE
Murata USA: [phone] USA: [phone] www.murata.com
Taiyo Yuden [phone] [phone] www.t-yuden.com
TDK [phone] [phone] www.component.tdk.com
AVX [phone] [phone] www.avxcorp.com
SHDN
GND
V
IN
SW
GND
V
OUT
LTC3525
SHDN
V
IN
3525 F03
V
OUT
OPERATION