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LT3465A Datasheet PDF : 12 Pages
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LT3465A
APPLICATIO S I FOR ATIO
Inductor Selection
A 22µH or 10µH inductor is recommended for most
LT3465A applications. Although small size and high effi-
ciency are major concerns, the inductor should have low
core losses at 1.2MHz and low DCR (copper wire resis-
tance). Some inductors in this category with small size are
listed in Table␣ 1. The efficiency comparison of different
inductors is shown in Figure 4.
Table 1. Recommended Inductors
PART
NUMBER
CURRENT RATING
DCR (Ω)
(mA)
LQH32CN220
0.71
250
ELJPC220KF
4.0
160
CDRH3D16-220 0.53
350
LB2012B220M 1.7
75
LEM2520-220
5.5
125
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
Capacitor Selection
The small size of ceramic capacitors makes them ideal for
LT3465A applications. X5R and X7R types are recom-
mended 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 0.22µF output
capacitor are sufficient for most LT3465A applications.
Table 2. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
PHONE
URL
Taiyo Yuden
408-573-4150
www.t-yuden.com
Murata
814-237-1431
www.murata.com
Kemet
408-986-0424
www.kemet.com
Inrush Current
The LT3465A has a built-in Schottky diode. When supply
voltage is applied to the VIN pin, the voltage difference
between VIN and VOUT generates inrush current flowing
from input through the inductor and the Schottky diode to
charge the output capacitor to VIN. The maximum current
the Schottky diode in the LT3465A can sustain is 1A. The
selection of inductor and capacitor value should ensure
the peak of the inrush current to be below 1A. The peak
inrush current can be calculated as follows:
80
VIN = 3.6V
4 LEDS
75
70
65
60
MURATA LQH32CN220
MURATA LQH32CN100
MURATA LQH2MCN220
55
TOKO D312-220
TOKO D312-100
TAIYO YUDEN LB2012B220
50
0
5
10
15
20
LED CURRENT (mA)
3465 F04
Figure 4. Efficiency Comparison of Different Inductors
IP
=
VIN
L
– 0.6
•ω
• exp –
α
ω
•a
tan
ω
α
• sina
tan
ω
α
α
=
r + 1.5
2•L
ω=
1
L•C
–
(r + 1.5)2
4 • L2
where L is the inductance, r is the resistance of the
inductor and C is the output capacitance. For low DCR
inductors, which is usually the case for this application,
the peak inrush current can be simplified as follows:
IP
=
VIN – 0.6
L•ω
• exp –
α
ω
•
π
2
3465ai
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