Datasheet

LTC3534
12
3534fb
For more information www.linear.com/LTC3534
applicaTions inForMaTion
FB
V
C
V
IN
PV
IN
V
OUT
PWM
RUN/SS
GND
PGND1
SW1
SW2
PGND2
2
3
4
5
6
7
15
14
13
12
11
10
3534 F04
V
IN
V
OUT
PWM
MULTIPLE VIAS
Figure 4. Recommended Component Placement. Traces Carrying High Current are Direct. Trace Area at FB and V
C
Pins
are Kept Low. Lead Length to Battery Should be Kept Short. Keep V
OUT
and V
IN
Ceramic Capacitors Close to their IC Pins.
Inductor Selection
The high frequency operation of the LTC3534 allows the
use of small surface mount inductors. The inductor ripple
current is typically set to 20% to 40% of the maximum
inductor current. For a given ripple the inductance terms
are given as follows:
L
BOOST
>
V
IN(MIN)
• V
OUT
– V
IN(MIN)
( )
f • ∆I
L
• V
OUT
H
L
BUCK
>
V
OUT
• V
IN(MAX)
– V
OUT
( )
f • ∆I
L
• V
IN(MAX)
H
where f = switching frequency in Hz, typically 1MHz.
DI
L
= maximum allowable inductor ripple current, A
V
IN(MIN)
= minimum input voltage, V
V
IN(MAX)
= maximum input voltage, V
V
OUT
= output voltage, V
For high efficiency, choose a ferrite inductor with a high
frequency core material to reduce core loses. The induc
-
tor should have low ESR (equivalent series resistance) to
reduce the I
2
R losses, and must be able to handle the peak
inductor current without saturating. Molded chokes or chip
inductors usually do not have enough core to support the
peak inductor currents in the 1A to 2A region. To minimize
radiated noise, use a shielded inductor. See Table 1 for a
suggested list of inductor suppliers.
Table 1. Inductor Vendor Information
SUPPLIER PHONE FAX OR E-MAIL WEBSITE
Coilcraft [phone] [phone] www.coilcraft.com
FDK [phone] [e-mail] www.fdk.com
Murata [phone]
[phone]
[phone] www.murata.com
Sumida USA: [phone]
Japan: 81(3) 3607-5111
USA: [phone]
Japan: 81(3) 3607-5144
www.sumida.com
TDK [phone] [phone] www.component.tdk.com
TOKO [phone] [phone] www.tokoam.com
COMPONENT SELECTION