LT3466 datasheet(13/20 Pages) LINER

13 / 20 page

LT3466

3466fa

APPLICATIO S I FOR ATIO

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

SW1

SW2

VIN

LT3466

VOUT1

63.4k

3466 F09

FB1

Ω

VOUT2

FB2

µH

2 AA CELLS

1.8V to 3V

µF

µH

0.1

µF

3.3V

µF

Ω

OFF ON

Figure 9. 2 AA Cells to Four White LEDs

COUT1

RFB1

CTRL1

CTRL2

3466 F10

RFB2

COUT2

CIN

VIN

GND

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 RT resistor, ensuring a clean,

noise-free connection. Recommended component place-

ment for the DFN package is shown in Figure 10.

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