LT3464 查看數據表（PDF） - Linear Technology
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LT3464 Datasheet PDF : 16 Pages
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LT3464
APPLICATIO S I FOR ATIO
Choosing an Inductor
The low current limit and fast switching of the LT3464
allow the use of very small surface mount inductors. The
minimum inductor size that may be used in a given
application depends on required efficiency and output
current. Some inductors that work with the LT3464 are
listed in Table 1, although there are many other manufac-
turers and devices that can be used. Consult each manu-
facturer for more detailed information and for their entire
selection of related parts. Many different sizes and shapes
are available.
Table 1. Recommended Inductors
PART NUMBER
µH DCR CURRENT
(Ω)
(mA)
LQH32CN680K53 68 2.2
130
LQH32CN470K53 47 1.3
170
LQH32CN220K53 22 0.71
250
ELJPC220KF
ELJPA470KF
22 4.0
160
47 2.25
135
CMD4D11-47
47 2.2
180
LB2016-220
22 1.0
105
LEM2520-220
22 5.5
125
LEM2520-330
33 7.1
110
LEMC2520-220 22 2.7
160
LEMC2520-330 33 4.8
120
LEMF2520-220 22 1.2
105
LEMC3225-680 68 3.3
120
LEMC3225-101 100 4.3
100
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
The following set of formulas can be used to calculate
maximum output current given VIN, VOUT and L values.
Inequality 1 is used to determine if the LT3464 is operating
in discontinuous mode. If the left hand side of inequality 1
evaluates to less than tOFF, then use Equation 3 to calculate
maximum output current. Otherwise, use Equation 2.
This inequality is true when the LT3464 is operating in
discontinuous mode.
(VOUT
LILIM
– VIN
+
VF )
<
tOFF
(INEQUALITY 1)
Use this equation to calculate the maximum output current
when the LT3464 is operating in continuous mode.
IOUT(CM) =
(2LILIM + tOFF(VIN – VOUT – VF ))(VIN – VCESAT )
(2)
2L(VOUT – VCESAT + VF )
Use this equation to calculate the maximum output current
when the LT3464 is operating in discontinuous mode.
IOUT(DCM) =
LILIM2 (VIN – VCESAT )
(3)
2(LILIM + VIN tOFF – tOFF VCESAT )(–VIN + VOUT + VF )
Where VF is the Schottky forward voltage, ILIM is the switch
current limit, tOFF is the switch off time, and VCESAT is the
switch saturation voltage. See the Electrical Specifications.
Figures 1 through 3 show the worst-case maximum output
current as given by Equations 2 and 3 using 20% inductor
derating and worst-case LT3464 specifications. Also note
that for some applications the maximum output current is
limited to 25mA by the output disconnect circuitry.
17.5
15.0
L = 47µH
12.5
L = 22µH
10.0
7.5
L = 10µH
5.0
2.5
L = 4.7µH
0
10
15
20 25
VOUT (V)
30 35
3464 F01
Figure 1. Maximum Output Current
VIN = 3.6V
8
25
20 L = 47µH
15
L = 22µH
L = 10µH
10
5
L = 4.7µH
0
10
15
20
25
VOUT (V)
30 35
3464 F02
Figure 2. Maximum Output Current
VIN = 5V
25
20
L = 47µH
15
L = 22µH
10
L = 10µH
5
L = 4.7µH
0
15
20
25
30
VOUT (V)
35
3464 F03
Figure 3. Maximum Output Current
VIN = 8.4V
3464f
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