lt3591 Linear Technology Corporation, lt3591 Datasheet - Page 7

• Manufacturer Part Number: lt3591
• Description: White Led Driver With Integrated Schottky In 3mm X 2mm Dfn
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
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
VLF4012AT-
220MR51
VLCF4018T-
220MR49-2
VLCF4020T-
220MR56
LQH43CN220K03
NR4018T220M
NR4012T220M
CDRH3D18-
220NC
B82470-A1223-M
(µH)
22
22
22
22
22
22
22
22
L
CURRENT
RATING
(mA)
480
510
490
560
420
590
510
600
4.1 × 4.1 × 1.8
4.2 × 4.2 × 1.8 Taiyo Yuden
4.2 × 4.2 × 1.2
4.8 × 4.8 × 1.2 Epcos
4.8 × 3.4 × 2.8 Murata
DIMENSION
4 × 3.8 × 1.2 TDK
4.1 × 4.1 × 2
L × W × H
4 × 4 × 2
(mm)
MAX
Figure 3. Effi ciency Comparison of Different Inductors
85
80
75
70
65
60
55
50
0
V
10 LEDs
IN
www.tdk.com
www.murata.com
www.t-yuden.com
Sumida
www.sumida.com
www.epcos.com
VENDOR
= 3.6V
5
LED CURRENT (mA)
10
TAIYO YUDEN NR4018T220M
TDK VLCF4018T-220MR49-2
TAIYO YUDEN NR4012T220M
TDKVLCF4012AT-220MR51
MURATA LQH43CN220K03
TDK VLCF4020T-220MR56
SUMIDA CDRH3D18-220NC
EPCOS B82470-A1223-M
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
GRM21BR71H105KA12L
GRM31MR71H105KA88
GRM31CR71H225KA88
GRM31CR71H475KA12L 4.7
UMK316BJ475KL-T
15
3591 F03
20
(µF)
2.2
4.7
C
1
1
VOLTAGE CASE SIZE
TEMP.
X7R
50V
X7R
50V
X7R
50V
X7R
50V
X7R
50V
1.25 ± 0.15
1.15 ± 0.1
1.6 ± 0.2
1.6 ± 0.2
1.6 ± 0.2
HEIGHT
(mm)
0805
1206
1206
1206
1206
Murata
www.murata.com
Taiyo Yuden
www.t-yuden.com
LT3591
VENDOR
7
3591f