LT3463/LT3463A
APPLICATIO S I FOR ATIO
Choosing an Inductor
Several recommended inductors that work well with the
LT3463 are listed in Table 1, although there are many other
manufacturers and devices that can be used. Consult each
manufacturer for more detailed information and for their
entire selection of related parts. Many different sizes and
shapes are available. Use the equations and recommenda-
tions in the next few sections to find the correct inductance
value for your design.
Table 1. Recommended Inductors
PART
CMD4D06
MAX
MAX HEIGHT
L (
µ
H) I
DC
(mA) DCR(
Ω
) (mm) MANUFACTURER
4.7
750
0.22
0.8
Sumida
10
500
0.46
(847) 956-0666
22
310
1.07
www.sumida.com
10
500
0.19
1.8
Sumida
22
310
0.36
4.7
600
0.16
1.2
Coilcraft
10
400
0.30
(847) 639-6400
22
280
0.64
www.coilcraft.com
10
450
0.39
1.8
Murata
15
300
0.75
(714) 852-2001
22
250
0.92
www.murata.com
4.7
340
0.85
1.8
Murata
CDRH3D16
LPO4812
LQH32C
LQH31C
Inductor Selection—Boost Regulator
The formula below calculates the appropriate inductor
value to be used for a boost regulator using the LT3463 (or
at least provides a good starting point). This value pro-
vides a good tradeoff in inductor size and system perfor-
mance. Pick a standard inductor close to this value. A
larger value can be used to slightly increase the available
output current, but limit it to around twice the value
calculated below, as too large of an inductance will in-
crease the output voltage ripple without providing much
additional output current. A smaller value can be used
(especially for systems with output voltages greater than
12V) to give a smaller physical size. Inductance can be
calculated as:
L
=
V
OUT
−
V
IN
(
MIN
)
+
V
D
I
LIM
t
OFF
where V
D
= 0.5V (Schottky diode voltage), I
LIM
= 250mA
(or 400mA) and t
OFF
= 300ns; for designs with varying V
IN
U
such as battery powered applications, use the minimum
V
IN
value in the above equation. For most regulators with
output voltages below 7V, a 4.7µH inductor is the best
choice, even though the equation above might specify a
smaller value.
For higher output voltages, the formula above will give
large inductance values. For a 3V to 20V converter (typical
LCD Bias application), a 21µH inductor is called for with
the above equation, but a 10µH inductor could be used
without much reduction in the maximum output current.
Inductor Selection—Inverting Regulator
The formula below calculates the appropriate inductor
value to be used for an inverting regulator using the
LT3463 (or at least provides a good starting point). This
value provides a good tradeoff in inductor size and system
performance. Pick a standard inductor close to this value
(both inductors should be the same value). A larger value
can be used to slightly increase the available output
current, but limit it to around twice the value calculated
below, as too large of an inductance will increase the
output voltage ripple without providing much additional
output current. A smaller value can be used (especially for
systems with output voltages greater than 12V) to give a
smaller physical size. Inductance can be calculated as:
W
U
U
V
OUT
+
V
D
L
=
2
I
LIM
t
OFF
where V
D
= 0.5V (Schottky diode voltage), I
LIM
= 250mA
(or 400mA) and t
OFF
= 300ns.
For higher output voltages, the formula above will give
large inductance values. For a 3V to 20V converter (typical
LCD bias application), a 49µH inductor is called for with
the above equation, but a 10µH or 22µH inductor could be
used without much reduction in the maximum output
current.
Inductor Selection—Inverting Charge Pump Regulator
For the inverting regulator, the voltage seen by the internal
power switch is equal to the sum of the absolute value of
the input and output voltages, so that generating high
3463f
5
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
