13
LT3466
3466fa
APPLICATIO S I FOR ATIO
WUUU
Figure 9 shows four LEDs being powered off two AA cells.
The battery is connected to the inductors and the chip is
powered off 3.3V logic supply voltage.
CTRL1 CTRL2
R
T
SW1 SW2V
IN
LT3466
V
OUT1
63.4k
1%
3466 F09
FB1
10Ω
V
OUT2
FB2
L1
15µH
2 AA CELLS
1.8V to 3V
1µF
L2
15µH
0.1µF
3.3V
1µF
1µF
10Ω
OFF ON OFF ON
Figure 9. 2 AA Cells to Four White LEDs
1
2
3
4
5
10
9
8
7
6
C
OUT1
R
FB1
R
T
CTRL1
CTRL2
3466 F10
R
FB2
C
OUT2
C
IN
V
IN
GND
GND
L1
L2
11
Figure 10. Recommended Component Placement (DFN Package)
HIGH INPUT VOLTAGE APPLICATIONS
The input voltage to the LT3466 can be as high as 24V. This
gives it the flexibility of driving a large number of LEDs
when being powered off a higher voltage. The maximum
number of LEDs that can be driven is constrained by the
converter output voltages being clamped at 39.5V (typ).
The LT3466 can be used to drive 20 White LEDs (10 per
converter) at 20mA when powered off two Li-Ion cells in
series.
BOARD LAYOUT CONSIDERATION
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 essen-
tial. Minimize the length and area of all traces connected to
the switching node pins (SW1 and SW2). Keep the feed-
back pins (FB1 and FB2) away from the switching nodes.
The exposed paddle for both DFN and TSSOP packages
must be connected to the system ground. The ground
connection for the feedback resistors should be tied
directly to the ground plane and not shared with any other
component, except the R
T
resistor, ensuring a clean,
noise-free connection. Recommended component place-
ment for the DFN package is shown in Figure 10.
