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PDF LTC3453 Data sheet ( Hoja de datos )
| Número de pieza | LTC3453 | |
| Descripción | Synchronous Buck-Boost High Power White LED Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3453www.DataSheet4U.com
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
VIN
1-CELL
Li-Ion
2.7V to 4.2V
2.2µF
L1
4.7µH
VIN PVIN SW1
SW2 VOUT 150mA/500mA
4.7µF
0.1µF
VC
EN1 (TORCH)
EN2 (FLASH)
8.25k
1%
3.48k
1%
EN1
EN2
ISET1
ISET2
1MHz
BUCK-BOOST
GND GND
LED1
LED2
LED3
LED4
D1
LTC3453
PGND 3453 TA01a
D1: LUMILEDS LXCL-PWF1
L1: VISHAY DALE IDCS-2512
EN1 EN2 ILED
0 0 0 (SHUTDOWN)
1 0 150mA
0 1 350mA
1 1 500mA
Torch Mode Efficiency vs VIN
100 180
90 160
EFFICIENCY
80 140
70
60
ILED = 150mA
50 TA = 25°C
2.7 3.1 3.5
IIN
3.9 4.3 4.7
VIN (V)
120
100
80
5.1 5.5
3453 TA01b
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BLOCK DIAGRA
OPTIONAL
LTC3453www.DataSheet4U.com
OPTIONAL
VIN
2.7V TO 5.5V
PVIN
16
1 VIN
UNDERVOLTAGE
LOCKOUT
UV
SWITCH A
15
SW1
14
SW2
SWITCH D
SWITCH B
GATE
DRIVERS
AND
ANTICROSS-
CONDUCTION
SWITCH C
OVERTEMP
PROTECTION
BANDGAP
REFERENCE
OT
1.23V
1612mA
FORWARD
CURRENT
LIMIT
+
–
REVERSE
CURRENT
LIMIT
200mA
+ LOGIC
–
AB PWM
COMPARATOR
UV
CD PWM
COMPARATOR
OT
VC
12
ISET1
3
RISET1
ISET2
10
RISET2
EN1
2
EN2
11
VBIAS
VFB
LED CURRENT
SETTING AMP 1
800mV
+
–
1MHz
OSCILLATOR
MAIN
– ERROR AMP
SAFETY
ERROR AMP
–
+
1.23V
+
SOFT
START
CLAMP
∑
ILED
384
VOUT
1.23V
327k
123k
800mV
LED CURRENT
+ SETTING AMP 2
–
ILED
384
SHUTDOWN
GND
5
GND
8
EXPOSED PAD (PGND)
17
VOUT
13
VOUT
LED1
4
LED
DETECT
LED2
6
LED
DETECT
LED3
7
LED
DETECT
LED4
9
LED
DETECT
OR
4
6
7
9
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LTC3453www.DataSheet4U.com
APPLICATIO S I FOR ATIO
Unused Outputs
If fewer than 4 LED pins are to be used, unused LEDx pins
should be connected to VOUT. The LTC3453 senses which
current source outputs are not being used and shuts off
the corresponding output currents to save power. A small
trickle current (~30µA) is still applied to unused outputs to
detect if a white LED is later switched in and also to
distinguish unused outputs from used outputs during
startup.
LED Failure Modes
If an individual LED fails as a short circuit, the current
source biasing it is shut off to save power. This is the same
operation as described previously (if the output were
initially designated unused at power-up by connecting its
LEDx pin to VOUT). Efficiency is not materially affected.
If an individual LED fails as an open circuit, the control loop
will initially attempt to regulate off of its current source
feedback signal, since it will appear to be the one requiring
the largest forward voltage drop to run at its programmed
current. This will drive VOUT higher. As the open circuited
LED will never accept its programmed current, VOUT must
be voltage-limited by means of a secondary control loop.
The LTC3453 limits VOUT to 4.5V in this failure mode. The
other LEDs will still remain biased at the correct pro-
grammed current but the overall circuit efficiency will
decrease.
PACKAGE DESCRIPTIO
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
0.72 ±0.05
4.35 ± 0.05
2.15 ± 0.05
2.90 ± 0.05 (4 SIDES)
PACKAGE OUTLINE
0.30 ±0.05
0.65 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
4.00 ± 0.10
(4 SIDES)
PIN 1
TOP MARK
(NOTE 6)
0.75 ± 0.05
2.15 ± 0.10
(4-SIDES)
BOTTOM VIEW—EXPOSED PAD
R = 0.115
TYP
15 16
PIN 1 NOTCH R = 0.20 TYP
OR 0.35 × 45° CHAMFER
0.55 ± 0.20
1
2
0.200 REF
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
(UF16) QFN 1004
0.30 ± 0.05
0.65 BSC
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC3453.PDF ] | |
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