LTC3525-3_15 Datasheet, PDF (12/16 Pages) Linear Technology – 400mA Micropower Synchronous Step-Up DC/DC Converter with Output Disconnect

LTC3525-3/
LTC3525-3.3/LTC3525-5
Operation
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.
Table 1. Inductor Vendor Information
SUPPLIER
PHONE
Murata
USA: [phone]
Coilcraft
[phone]
Sumida
USA: [phone]
Taiyo Yuden [phone]
TOKO
[phone]
TDK
[phone]
Würth
[phone]
FAX
USA: [phone]
[phone]
USA: [phone]
[phone]
[phone]
[phone]
[phone]
WEBSITE
www.murata.com
www.coilcraft.com
www.sumida.com
www.t-yuden.com
www.toko.co.jp/products/en
www.tdk.com
www.we-online.com
Table 2. Capacitor Vendor Information
SUPPLIER
PHONE
Murata
USA: [phone]
Taiyo Yuden [phone]
TDK
[phone]
AVX
[phone]
FAX
USA: [phone]
[phone]
[phone]
[phone]
WEBSITE
www.murata.com
www.t-yuden.com
www.component.tdk.com
www.avxcorp.com
12
SHDN
V_IN
SHDN SW
LTC3525
GND GND
V_IN
V_OUT
3525 F03
V_OUT
Figure 3. Recommended Component Placement
For more information www.linear.com/LTC3525
3525fc