Datasheet

11
LT3466-1
34661f
APPLICATIO S I FOR ATIO
WUUU
The inductor current ripple (∆I
L
), neglecting the drop
across the Schottky diode and the switch, is given by :
∆ =
()
I
VV V
VfL
L
IN MIN OUT MAX IN MIN
OUT MAX
() ( ) ()
()
•–
••
where:
L = Inductor
f = Operating frequency
V
IN(MIN)
= Minimum input voltage
V
OUT(MAX)
= Maximum output voltage
The ∆I
L
is typically set to 20% to 40% of the maximum
inductor current.
The inductor should have a saturation current rating
greater than the peak inductor current required for the
application. Also, ensure that the inductor has a low DCR
(copper wire resistance) to minimize I
2
R power losses.
Recommended inductor values range from 10µH to 68µH.
Several inductors that work well with the LT3466
-1 are listed
in Table 1. Consult each manufacturer for more detailed
information and for their entire selection of related parts.
Table 1. Recommended Inductors
MAX CURRENT
L DCR RATING
PART (µH) (Ω) (mA) VENDOR
LQH32CN100 10 0.44 300 Murata
LQH32CN150 15 0.58 300 [phone]
LQH43CN330 33 1.00 310 www.murata.com
ELL6RH330M 33 0.38 600 Panasonic
ELL6SH680M 68 0.52 500 [phone]
www.panasonic.com
A914BYW330M 33 0.45 440 Toko
A914BYW470M 47 0.73 360 www.toko.com
A920CY680M 68 0.40 400
CDRH2D18150NC 15 0.22 0.35A Sumida
CDRH4D18-330 33 0.51 0.31A [phone]
CDRH5D18-680 68 0.84 0.43A www.sumida.com
CAPACITOR SELECTION
The small size of ceramic capacitors make them ideal for
LT3466-1 applications. Use only X5R and X7R types
because they retain their capacitance over wider voltage
and temperature ranges than other types such as Y5V or
Z5U. A 1µF input capacitor is sufficient for most applica-
tions. Always use a capacitor with sufficient voltage rating.
Table 2 shows a list of several ceramic capacitor manufac-
turers. Consult the manufacturers for detailed information
on their entire selection of ceramic parts.
Table 2. Ceramic Capacitor Manufacturers
Taiyo Yuden [phone]
www.t-yuden.com
AVX [phone]
www.avxcorp.com
Murata [phone]
www.murata.com
INRUSH CURRENT
The LT3466-1 has built-in Schottky diodes. When supply
voltage is applied to the V
IN
pin, an inrush current flows
through the inductor and the Schottky diode and charges
up the output capacitor. Both Schottky diodes in the
LT3466 -1 can sustain a maximum of 1A current. The
selection of inductor and capacitor value should ensure
the peak of the inrush current to be below 1A.
For low DCR inductors, which is usually the case for this
application, the peak inrush current can be simplified as
follows:
I
V
L
where
LC
PK
IN
OUT
=
=
–.
:
06
1
ω
ω
Table 3 gives inrush peak current for some component
selections.
Table 3. Inrush Peak Current
V
IN
(V) L (µH) C
OUT
(µF) I
P
(A)
5 15 0.47 0.78
5 33 1.00 0.77
5 47 2.2 0.95
5 68 1.00 0.53
9 47 0.47 0.84
12 33 0.22 0.93