LTC3490 Datasheet, PDF (1/12 Pages) Linear Technology – Single Cell 350mA LED Driver

LTC3490
Single Cell 350mA
LED Driver
FEATURES
■ _{350mA Constant Current Output}
■ _{2.8V to 4V Output Compliance}
■ _{1- or 2-Cell NiMH or Alkaline Input}
■ _{Synchronous Rectification: Up to 90% Efficiency}
■ _{Fixed Frequency Operation: 1.3MHz}
■ _{Low Quiescent Current: <1mA}
■ _{Very Low Shutdown Current: <50µA}
■ _{Open LED Output Limited to 4.7V}
■ _{VIN Range: 1V to 3.2V}
■ _{Dimming Control}
■ _{Undervoltage Lockout to Protect Batteries}
■ _{Low Profile (0.75mm) 3mm × 3mm Thermally}
Enhanced 8-Lead DD and S8 Packages
U
APPLICATIO S
■ _{Portable Lighting}
■ _{Rechargeable Flashlights}
DESCRIPTIO
The LTC^®3490 provides a constant current drive for 1W
LED applications. It is a high efficiency boost converter
that operates from 1 or 2 NiMH or alkaline cells and
generates 350mA of constant current with up to 4V of
compliance. It contains a 100mΩ NFET switch and a
130mΩ PFET synchronous rectifier. The fixed switching
frequency is internally set to 1.3MHz.
The LTC3490 limits the output voltage to 4.7V if the output
load is disconnected. It also features an analog dimming
capability that reduces the drive current proportional to
the CTRL/SHDN pin voltage. A low-battery logic output
signals when the battery has dropped below 1V/cell. An
undervoltage lockout circuit shuts down the LTC3490
when the battery voltage drops below 0.85V/cell. The
feedback loop is internally compensated to minimize com-
ponent count.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
Single Cell Minimum Component LED Driver
3.3µH
1 NiMH OR ₊
ALKALINE
CELL
V_IN
SW
ON/OFF
CAP
LTC3490
350mA
CTRL/SHDN LED
CELLS LOBAT
1M
GND
4.7µF
HIGH
CURRENT
LED
3490 TA01
Efficiency vs V_IN at V_LED = 3.5V
100
I_OUT = 350mA
90
80
70
60
50
40
30
20
10
0
1
1.5
2
V_IN (V)
2.5
3
3490 TA02
3490fa
1