Datasheet

LT3593
8
3593f
APPLICATIONS INFORMATION
Inductor Selection
A 10µH inductor is recommended for most LT3593 ap-
plications. Although small size and high effi ciency are
major concerns, the inductor should have low core losses
at 1MHz and low DCR (copper wire resistance). Some
inductors in this category with small size are listed in
Table 1. The effi ciency comparison of different inductors
is shown in Figure 4.
Table 1. Recommended Inductors
PART
L
(μH)
DCR
()
CURRENT
RATING
(mA) VENDOR
LQH43CN100
LQH32CN100
10
10
0.24
0.44
650
450
Murata
NR3010T100M 10 0.45 500 Taiyo Yuden
VLF4012AT-100M
VLF3010AT-100M
10
10
0.20
0.58
500
490
TDK
DE2812-1098AS-100M
DB3015C-1068AS-100M
10
10
0.29
0.38
580
400
TOKO
Capacitor Selection
The small size of ceramic capacitors makes them ideal
for LT3593 applications. Use only X5R and X7R types
because they retain their capacitance over wider voltage
and temperature ranges than other types such as Y5V or
Z5U. A 1µF input capacitor and a 1µF output capacitor are
suffi cient for most applications.
Table 2 shows a list of several ceramic capacitor manufac-
turers. Consult the manufacturers for detailed information
on their entire selection of ceramic parts.
Table 2. Recommended Ceramic Capacitor Manufacturers
Taiyo Yuden [phone]
www.t-yuden.com
AVX [phone]
www.avxcorp.com
Murata [phone]
www.murata.com
Kemet [phone]
www.kemet.com
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast reverse recovery, are the ideal choices for LT3593 ap-
plications. The forward voltage drop of a Schottky diode
represents the conduction losses in the diode, while the
diode capacitance (C
T
or C
D
) represents the switching
losses. For diode selection, both forward voltage drop and
diode capacitance need to be considered. Schottky diodes
with higher current ratings usually have lower forward
voltage drop and larger diode capacitance, which can
cause signifi cant switching losses at the 1.0MHz switching
frequency of the LT3593. A Schottky diode rated at 400mA
to 500mA is suffi cient for most LT3593 applications. Some
recommended Schottky diodes are listed in Table 3.
Table 3. Recommended Schottky Diodes
PART
NUMBER
FORWARD
CURRENT
(mA)
VOLTAGE
DROP
(V)
DIODE
CAPACITANCE
(pF) MANUFACTURER
CMDSH05-4 500 0.47 at
500mA
50 at 1V Central
631-435-1110
www.centralsemi.com
CMMSH1-40 1000 0.55 at
1A
80 at 4V
ZLL5400 520 0.50 at
400mA
15 at 30V Zetex
631-543-7100
www.zetex.com
PMEG-
4005AEA
500 0.47 at
500mA
50 at 1V Phillips
[phone]
www.semiconductors.
phillips.com
Figure 4. Effi ciency Comparison of Different Inductors
LED CURRENT (mA)
0.00
EFFI CIENCY (%)
90.00
70.00
50.00
80.00
60.00
40.00
30.00
10.00
3593 F04
20.0015.005.00
NR3010T100M
VLF4012-AT-100MR50
LQH43CN100K03
VLF3010AT-100MR49
LQH32CN100K53
DB3015C-1068AS-100M