LTC3490 Datasheet, PDF (4/12 Pages) Linear Technology – Single Cell 350mA LED Driver

LTC3490
TYPICAL PERFOR A CE CHARACTERISTICS
I_LED vs V_LED
360
V_IN = 2.4V
358
356
354
352
350
348
346
344
342
340
2.8 3
3.2 3.4 3.6
V_LED (V)
3.8 4
3490 G04
Efficiency vs I_LED
100
V_IN = 2.4V
90
80
70
V_IN = 1.2V
60
50
40
30
20
10
0
0
100
200
300
400
I_LED (mA)
3490 G05
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
V_IN) will set the thresholds for 2 cells.
V_IN (Pin 2): Supply Voltage.
SW (Pin 3): Switch Input. Connect this pin to an external
inductor from V_IN.
GND (Pin 4): Circuit Ground.
LED (Pin 5): Output Drive Current to LED.
CAP (Pin 6): Filter Capacitor. A 4.7µF 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 V_IN • 0.2 < V_CTRL < V_IN • 0.9, the LED drive
current varies according to the formula:
I_LED
=
500
•
⎛
⎝⎜
V_CTRL
V_IN
–
0.2^{⎞⎠⎟}
mA
When V_CTRL > V_IN • 0.9, the LED drive current is clamped
at 350mA. When V_CTRL < V_IN • 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.
3490fa
4