LTC3490EDD datasheet(4/12 Pages) LINER

4 / 12 page

LTC3490

3490fa

PI FU CTIO S

CELLS (Pin 1): A logic input to set the low-battery and

undervoltage shutdown thresholds. A logic low (tied to

GND) will set the thresholds for 1 cell. A logic high (tied to

VIN) will set the thresholds for 2 cells.

VIN (Pin 2): Supply Voltage.

SW (Pin 3): Switch Input. Connect this pin to an external

inductor from VIN.

GND (Pin 4): Circuit Ground.

LED (Pin 5): Output Drive Current to LED.

CAP (Pin 6): Filter Capacitor. A 4.7

µF low ESR capacitor

should be tied to this pin.

LOBAT (Pin 7): Low active, open-drain logic output indi-

cating a low-battery condition.

CTRL/SHDN (Pin 8): Analog Control Voltage and Shut-

down. When VIN • 0.2 < VCTRL < VIN • 0.9, the LED drive

current varies according to the formula:

LED

CTRL

⎛

⎝⎜

⎞

⎠⎟

500

0 2

•– .

When VCTRL > VIN • 0.9, the LED drive current is clamped

at 350mA. When VCTRL < VIN • 0.2, then the part is in low

power shutdown.

Exposed Pad (Pin 9, DD Package): Ground. This pin must

be soldered to the PCB to provide both electrical contact

to ground and good thermal contact to the PCB.

ILED vs VLED

VLED (V)

2.8

340

342

346

348

350

360

354

3.2

3.4

3.6

3.8

3490 G04

344

356

358

352

VIN = 2.4V

TYPICAL PERFOR A CE CHARACTERISTICS

ILED (mA)

100

200

3490 G05

300

400

VIN = 2.4V

VIN = 1.2V

Efficiency vs ILED

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