LT3465 LINER [Linear Technology], LT3465 Datasheet - Page 6

• Manufacturer Part Number: LT3465
• Description: 1.2MHz/2.4MHz White LED Step-Up Converters with Built-In Schottky in ThinSOT
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LT3465/LT3465A
reaches zero during the discharge phase. After the induc-
tor current reaches zero, the SW pin exhibits ringing due
to the LC tank circuit formed by the inductor in combina-
tion with switch and diode capacitance. This ringing is
not harmful; far less spectral energy is contained in the
ringing than in the switch transitions. The ringing can be
damped by application of a 300
inductor, although this will degrade efficiency. Because
of the higher switching frequency, the LT3465A can drive
a 3-LED string at 0.2mA LED current without pulse
skipping. The photo in Figure 3b detials circuit operation
driving three white LEDs at a 0.2mA load. Peak inductor
current is less than 30mA.
Inductor Selection
A 22 H inductor is recommended for most LT3465 appli-
cations. Although small size and high efficiency are major
concerns, the inductor should have low core losses at
1.2MHz and low DCR (copper wire resistance). Some
inductors in this category with small size are listed in
Table 1. The efficiency comparison of different inductors
is shown in Figure 4a. A 22 H or 10 H inductor is
recommended for most LT3465A applications. The induc-
tor should have low core losses at 2.4MHz and low DCR.
The efficiency comparison of different inductors is shown
in figure 4b.
Table 1. Recommended Inductors
PART
NUMBER
LQH32CN220
LQH2MCN220
ELJPC220KF
CDRH3D16-220
LB2012B220M
LEM2520-220
6
DCR ( )
0.71
0.53
2.4
4.0
1.7
5.5
U
CURRENT RATING
U
(mA)
250
185
160
350
125
75
W
resistor across the
MANUFACTURER
Murata
814-237-1431
www.murata.com
Panasonic
714-373-7334
www.panasonic.com
Sumida
847-956-0666
www.sumida.com
Taiyo Yuden
408-573-4150
www.t-yuden.com
Taiyo Yuden
408-573-4150
www.t-yuden.com
U
Capacitor Selection
The small size of ceramic capacitors makes them ideal for
LT3465 and LT3465A applications. X5R and X7R types are
recommended because they retain their capacitance over
wider voltage and temperature ranges than other types
such as Y5V or Z5U. A 1 F input capacitor and a 0.22 F
output capacitor are sufficient for most LT3465 and
LT3465A applications.
Table 2. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
Taiyo Yuden
Murata
Kemet
Figure 4b. Efficiency Comparison of Different Inductors (LT3465A)
Figure 4a. Efficiency Comparison of Different Inductors (LT3465)
85
55
50
55
50
80
75
70
65
60
80
75
70
60
65
0
0
V
4 LEDs
V
4 LEDs
IN
IN
= 3.6V
= 3.6V
5
5
PHONE
408-573-4150
814-237-1431
408-986-0424
LED CURRENT (mA)
LED CURRENT (mA)
MURATA LQH32CN220
TAIYO YUDEN LB2012B220M
TAIYO YUDEN CB2012B220
MURATA LQH32CN220
MURATA LQH32CN100
MURATA LQH2MCN220
TOKO D312-220
TOKO D312-100
TAIYO YUDEN LB2012B220
10
10
15
15
www.t-yuden.com
www.murata.com
URL
www.kemet.com
3465A F04b
3465A F04b
20
20
3465af