LT3494A データシートの表示（PDF） - Linear Technology
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LT3494A Datasheet PDF : 12 Pages
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LT3494/LT3494A
APPLICATIONS INFORMATION
the CAP pin will improve efficiency and lower the stress
placed on the internal Schottky diode.
Board Layout Considerations
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To maximize efficiency, switch rise and fall times are made
as short as possible. To prevent electromagnetic interfer-
ence (EMI) problems, proper layout of the high frequency
switching path is essential. The voltage signal of the SW pin
has sharp rising and falling edges. Minimize the length and
area of all traces connected to the SW pin and always use
a ground plane under the switching regulator to minimize
interplane coupling. In addition, the FB connection for
the feedback resistor R1 should be tied directly from the
Vout pin to the FB pin and be kept as short as possible,
ensuring a clean, noise-free connection. Recommended
component placement is shown in Figure 4.
TYPICAL APPLICATIONS
VIN
3V TO 4.2V
L1
15μH
C2
4.7μF
1
8
SW CAP
3
VCC
7
VOUT
TURN ON/OFF
VOUT DIMMING
LT3494
5 SHDN
FB 6
4
2
CTRL GND
C1
0.22μF
VOUT
R1
C3
2.2μF
3494 F05
C1, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING
C3: MURATA GRM31MR71E225K
L1: MURATA LQH32CN150K53
Figure 5. One Li-Ion Cell Input Boost Converter with the LT3494
R1 VALUE REQUIRED MAXIMUM OUTPUT CURRENT AT
VOUT
(MΩ)
3V INPUT (mA)
25
3.57
8.6
24
3.40
9.3
23
3.24
10.0
22
3.09
10.6
21
2.94
11.3
20
2.80
12.1
19
2.67
12.9
18
2.49
13.6
17
2.37
14.8
16
2.21
16.0
15
2.05
17.2
10
GND
SW
CAP
GND
VOUT
GND
VCC
FB
CTRL
SHDN
3494 F04
CTRL
SHDN
VIAS TO GROUND PLANE REQUIRED
TO IMPROVE THERMAL PERFORMANCE
Figure 4. Recommended Layout
3.6V to 16V Efficiency
90
280
VIN = 3.6V
LOAD FROM
80
CAPACITOR
240
70
LOAD FROM
200
VOUT
60
160
50
120
40
80
30
40
20
0.1
1
10
LOAD CURRENT (mA)
0
100
3494 TA01c
3494fb
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