Datasheet

LT3591
7
3591f
INDUCTOR SELECTION
A 22µH inductor is recommended for most LT3591 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
small inductors in this category are listed in Table 1. The
effi ciency comparison of different inductors is shown in
Figure 3.
Table 1. Recommended Inductors
PART
L
(µH)
CURRENT
RATING
(mA)
MAX
DIMENSION
L × W × H
(mm) VENDOR
VLF4012AT-
220MR51
22 510
4
× 3.8 × 1.2
TDK
www.tdk.com
VLCF4018T-
220MR49-2
22 490
4.1
× 4.1 × 1.8
VLCF4020T-
220MR56
22 560
4.1
× 4.1 × 2
LQH43CN220K03 22 420
4.8
× 3.4 × 2.8
Murata
www.murata.com
NR4018T220M 22 590
4.2
× 4.2 × 1.8
Taiyo Yuden
www.t-yuden.com
NR4012T220M 22 510
4.2
× 4.2 × 1.2
CDRH3D18-
220NC
22 600
4 × 4
× 2
Sumida
www.sumida.com
B82470-A1223-M 22 480
4.8
× 4.8 × 1.2
Epcos
www.epcos.com
APPLICATIONS INFORMATION
CAPACITOR SELECTION
The small size of ceramic capacitors make them ideal for
LT3591 applications. Use only X5R and X7R types because
they retain their capacitance over wider temperature
ranges than other types such as Y5V or Z5U. A 1µF input
capacitor and a 50V, 2.2µF output capacitor are suffi cient
for most applications.
A limited number of manufacturers produce small 50V
capacitors. Table 2 shows a list of several recommended
50V capacitors. Consult the manufacturer for detailed
information on their entire selection of ceramic parts.
Table 2. Recommended Output Capacitors
PART
C
(µF)
VOLTAGE CASE SIZE
VENDORTEMP.
HEIGHT
(mm)
GRM21BR71H105KA12L 1 50V 0805 Murata
www.murata.com
X7R 1.25 ± 0.15
GRM31MR71H105KA88 1 50V 1206
X7R 1.15 ± 0.1
GRM31CR71H225KA88 2.2 50V 1206
X7R 1.6 ± 0.2
GRM31CR71H475KA12L 4.7 50V 1206
X7R 1.6 ± 0.2
UMK316BJ475KL-T 4.7 50V 1206 Taiyo Yuden
www.t-yuden.com
X7R 1.6 ± 0.2
Figure 3. Effi ciency Comparison of Different Inductors
LED CURRENT (mA)
0
50
EFFICIENCY (%)
55
85
80
65
5
10
3591 F03
70
75
60
15
20
TAIYO YUDEN NR4018T220M
TDK VLCF4018T-220MR49-2
TAIYO YUDEN NR4012T220M
TDKVLCF4012AT-220MR51
MURATA LQH43CN220K03
TDK VLCF4020T-220MR56
SUMIDA CDRH3D18-220NC
EPCOS B82470-A1223-M
V
IN
= 3.6V
10 LEDs