11
LT3466
3466fa
APPLICATIO S I FOR ATIO
WUUU
INDUCTOR SELECTION
The choice of the inductor will depend on the selection of
the switching frequency of the LT3466. The switching
frequency can be programmed from 200kHz to 2MHz.
Higher switching frequency allows the use of smaller
inductors albeit at the cost of increased switching losses.
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 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 (814) 237-1431
LQH43CN330 33 1.00 310 www.murata.com
ELL6RH330M 33 0.38 600 Panasonic
ELL6SH680M 68 0.52 500 (714) 373-7939
www.panasonic.com
A914BYW330M 33 0.45 440 Toko
A914BYW470M 47 0.73 360 www.toko.com
A920CY680M 68 0.40 400
CDRH2D18150NC 15 0.22 350 Sumida
CDRH4D18-330 33 0.51 310 (847) 956-0666
CDRH5D18-680 68 0.84 430 www.sumida.com
CAPACITOR SELECTION
The small size of ceramic capacitors make them ideal for
LT3466 applications. Use only X5R and X7R types be-
cause 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 applications.
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 (408) 573-4150
www.t-yuden.com
AVX (803) 448-9411
www.avxcorp.com
Murata (714) 852-2001
www.murata.com
INRUSH CURRENT
The LT3466 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 voltage. Both the Schottky diodes in the
LT3466 can sustain a maximum of 1A current. The selec-
tion 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.
