LTC3453_15 Datasheet, PDF (1/12 Pages) Linear Technology – Synchronous Buck-Boost High Power White LED Driver

LTC3453
Synchronous Buck-Boost
High Power White LED Driver
FEATURES
■ _{High Efficiency: 90% Typical Over Entire}
Li-Ion Battery Range
■ _{Wide VIN Range: 2.7V to 5.5V}
■ _{Up to 500mA Continuous Output Current}
■ _{Internal Soft-Start}
■ _{Open/Shorted LED Protection}
■ _{LED Current Matching Typically <2%}
■ _{Constant Frequency 1MHz Operation}
■ _{Low Shutdown Current: 6µA}
■ _{Overtemperature Protection}
■ _{Small Thermally Enhanced 16-Lead (4mm x 4mm)}
QFN Package
U
APPLICATIO S
■ _{Cell Phones}
■ _{Digital Cameras}
■ _PDAs
■ _{Portable Devices}
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTIO
The LTC^®3453 is a synchronous buck-boost DC/DC con-
verter optimized for driving up to 4 white LEDs at a
combined current of up to 500mA from a single Li-Ion
battery input. The regulator operates in either synchro-
nous buck, synchronous boost, or buck-boost mode,
depending on input voltage and LED maximum forward
voltage. Optimum efficiency is achieved using a propri-
etary architecture that determines which LED requires the
largest forward voltage drop at its programmed current,
and regulates the common output rail for lowest dropout.
Efficiency of 90% can be achieved over the entire usable
range of a Li-Ion battery (2.7V to 4.2V).
LED current is programmable to one of four levels (includ-
ing shutdown) with dual current setting resistors and dual
enable pins. In shutdown, the supply current is only 6µA.
A high constant operating frequency of 1MHz allows the
use of a small external inductor. The LTC3453 is offered
in a low profile (0.75mm) thermally enhanced 16-lead
(4mm x 4mm) QFN package.
TYPICAL APPLICATIO
High Efficiency Torch/Flash LED Driver
V_IN
1-CELL
Li-Ion
2.7V to 4.2V
2.2µF
L1
4.7µH
V_IN PV_IN SW1
SW2 V_OUT ^150mA/500mA
4.7µF
0.1µF
V_C
EN1 (TORCH)
EN2 (FLASH)
8.25k
1%
3.48k
1%
EN1
EN2
I_SET1
I_SET2
1MHz
BUCK-BOOST
GND
GND
D1
LED1
LED2
LED3
LED4
LTC3453
PGND ^{3453 TA01a}
D1: LUMILEDS LXCL-PWF1
L1: VISHAY DALE IDCS-2512
EN1 EN2 I_LED
0 0 0 (SHUTDOWN)
1 0 150mA
0 1 350mA
1 1 500mA
Torch Mode Efficiency vs V_IN
100
180
90
160
EFFICIENCY
80
140
70
60
I_LED = 150mA
50 ^{TA = 25°C}
2.7 3.1 3.5
I_IN
3.9 4.3 4.7
V_IN (V)
120
100
80
5.1 5.5
3453 TA01b
3453fa
1