LT3591 查看數據表（PDF） - Linear Technology
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LT3591 Datasheet PDF : 16 Pages
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LT3591
APPLICATIONS INFORMATION
LOW INPUT VOLTAGE APPLICATIONS
The LT3591 can be used in low input voltage applications.
The input supply voltage to the LT3591 must be 2.5V or
higher. However, the inductor can be run off a lower battery
voltage. This technique allows the LEDs to be powered off
two alkaline cells. Most portable devices have a 3.3V logic
supply voltage which can be used to power the LT3591.
The LEDs can be driven straight from the battery, resulting
in higher efficiency.
Figure 10 shows six LEDs powered by two AA cells. The
battery is connected to the inductor and the chip is powered
off a 3.3V logic supply voltage.
3.3V
2 AA CELLS
2V TO 3.2V
C1
1µF
L1
15µH
SHUTDOWN AND
DIMMING CONTROL
VIN CTRL CAP
LT3591
LED
SW
GND
C1
1µF
RSENSE
10Ω
C2
4.7µF
BOARD LAYOUT CONSIDERATIONS
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
proper layout of high frequency switching paths is essential.
Minimize the length and area of all traces connected to
the switching node pin (SW). Keep the sense voltage pins
(CAP and LED) away from the switching node. Place COUT
next to the CAP pin. Always use a ground plane under the
switching regulator to minimize interplane coupling. Re-
commended component placement is shown in Figure 11.
CIN
VIN
1
2
L1 3
SW
4
CTRL
8
GND
7
LED
9
6
5 CAP
COUT
RSENSE
C1: TAIYO YUDEN EMK107BJ105MA
C2: MURATA GRM31CR71H475KA12L
L1: TAIYO YUDEN NR4018T150M
3591 F10
3591 F11
Figure 11. Recommended Component Placement
Figure 10. 2 AA Cells to Six White LEDs
3591f
11
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