LT3591
APPLICATIONS INFORMATION
INDUCTOR SELECTION
A 22µH inductor is recommended for most LT3591 ap-
plications. Although small size and high efficiency 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
efficiency comparison of different inductors is shown in
Figure 3.
Table 1. Recommended Inductors
CURRENT
RATING
(mA)
510
490
560
420
590
510
600
480
MAX
DIMENSION
L
×
W
×
H
(mm)
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 sufficient
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
VOLTAGE CASE SIZE
PART
GRM21BR71H105KA12L
4.1
×
4.1
×
2
4.8
×
3.4
×
2.8 Murata
www.murata.com
4.2
×
4.2
×
1.8 Taiyo Yuden
www.t-yuden.com
4.2
×
4.2
×
1.2
4
×
4
×
2
Sumida
www.sumida.com
GRM31MR71H105KA88
GRM31CR71H225KA88
1
2.2
C
(µF)
1
TEMP.
50V
X7R
50V
X7R
50V
X7R
GRM31CR71H475KA12L 4.7
UMK316BJ475KL-T
4.7
50V
X7R
50V
X7R
HEIGHT
(mm)
0805
1206
1.15 ± 0.1
1206
1.6 ± 0.2
1206
1.6 ± 0.2
Taiyo Yuden
1.6 ± 0.2 www.t-yuden.com
1206
VENDOR
PART
VLF4012AT-
220MR51
VLCF4018T-
220MR49-2
VLCF4020T-
220MR56
LQH43CN220K03
NR4018T220M
NR4012T220M
CDRH3D18-
220NC
B82470-A1223-M
L
(µH)
22
22
22
22
22
22
22
22
VENDOR
4
×
3.8
×
1.2 TDK
www.tdk.com
4.1
×
4.1
×
1.8
Murata
1.25 ± 0.15 www.murata.com
4.8
×
4.8
×
1.2 Epcos
www.epcos.com
85
80
75
EFFICIENCY (%)
70
65
60
55
50
0
V
IN
= 3.6V
10 LEDs
TAIYO YUDEN NR4018T220M
TDK VLCF4018T-220MR49-2
TAIYO YUDEN NR4012T220M
TDKVLCF4012AT-220MR51
MURATA LQH43CN220K03
TDK VLCF4020T-220MR56
SUMIDA CDRH3D18-220NC
EPCOS B82470-A1223-M
5
10
LED CURRENT (mA)
15
20
3591 F03
Figure 3. Efficiency Comparison of Different Inductors
3591f
7
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
