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PDF LTC3454 Data sheet ( Hoja de datos )
| Número de pieza | LTC3454 | |
| Descripción | 1A Synchronous Buck-Boost High Current LED Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3454www.DataSheet4U.com
1A Synchronous Buck-Boost
High Current LED Driver
FEATURES
■ High Efficiency: >90% Typical in Torch Mode,
>80% in Flash Mode
■ Wide VIN Range: 2.7V to 5.5V
■ Up to 1A Continuous Output Current
■ 3.5% LED Current Programming Accuracy
■ Internal Soft-Start
■ Open/Shorted LED Protection
■ Constant Frequency 1MHz Operation
■ Zero Shutdown Current
■ Overtemperature Protection
■ Small Thermally Enhanced 10-Lead (3mm × 3mm)
DFN Package
U
APPLICATIO S
■ Cell Phone Camera Flash
■ Cell Phone Torch Lighting
■ Digital Cameras
■ PDAs
■ Misc Li-Ion LED Drivers
DESCRIPTIO
The LTC®3454 is a synchronous buck-boost DC/DC
converter optimized for driving a single high power LED
at currents up to 1A from a single cell Li-Ion battery in-
put. The regulator operates in either synchronous buck,
synchronous boost, or buck-boost mode depending on
input voltage and LED forward voltage. PLED/PIN efficiency
greater than 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 external resistors and dual enable
inputs. In shutdown no supply current is drawn.
A high constant operating frequency of 1MHz allows the
use of small external components. The LTC3454 is offered
in a low profile (0.75mm) thermally enhanced 10-lead
(3mm × 3mm) DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
High Efficiency Torch/Flash LED Driver
VIN
1- CELL
Li-Ion
2.7V-4.2V
10mF
L1
5mH
VIN SW1
SW2 VOUT
10mF
ILED
A D LED
B
C LED
EN2 EN1 I LED
0 0 0 (SHUTDOWN)
0
EN1 (TORCH) 1
1 150mA
0 850mA
1 1 1A
0.1mF
VC
1MHz
BUCK-BOOST
LTC3454
LED: LUMILEDS LXL-PWF1
L1: SUMIDA CDRH6D28-5RONC
GND (EXPOSED PAD)
EN2 (FLASH)
ISET1
ISET2
RISET2
3.65k
1%
RISET1
20.5k
1%
3453 TA01a
LED Power Efficiency vs VIN
100
95 ILED = 150mA
90
85 ILED = 1A
80
75
70
65 TA = 25°C
EFFICIENCY = (VOUT – VLED)ILED/VINIIN
60
2.7 3.1 3.5 3.9 4.3 4.7 5.1
5.5
VIN (V)
3454 TA01b
3454f
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1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage Ripple
Back Page Application
Start-Up Transient
Back Page Application
20mV/DIV
VIN = 3.6V
ILED = 500mA
500ns/DIV
3454 G19
0V, 0A
0V
VIN = 3.6V
ILED = 500mA
5ms/DIV
LTC3454www.DataSheet4U.com
CH1, VOUT
1V/DIV
CH2, ILED
500mA
FINAL VALUE
CH3, VEN1
1V/DIV
3454 G19
PI FU CTIO S
EN1 (Pin 1): Enable Input Pin for ISET1 Current.
EN2 (Pin 2): Enable Input Pin for ISET2 Current.
ISET1 (Pin 3): LED Current Programming Pin. A resistor
to ground programs the current through the LED to ILED
= 3850(0.8V/RISET1). This amount of current adds to any
amount set by EN2/ISET2 if used.
ISET2 (Pin 4): LED Current Programming Pin. A resistor
to ground programs the current through the LED to ILED
= 3850(0.8V/RISET2). This amount of current adds to any
amount set by EN1/ISET1 if used.
LED (Pin 5): Low Dropout Output for LED Current Biasing.
Connect the LED between VOUT and the LED pin.
SW2 (Pin 6): Switching Node. External inductor con-
nects between SW1 and SW2. Recommended value is
4.7µH/5µH.
VOUT (Pin 7): Buck-Boost Output Rail. Bypass to GND with
a ceramic capacitor. Recommended value is 10µF.
VC (Pin 8): Compensation Point for the Internal Error
Amplifier Output. Connect a ceramic capacitor from VC
to GND. Recommended value is 0.1µF.
VIN (Pin 9): Voltage Input Supply Pin (2.7V ≤ VIN ≤ 5.5V).
Bypass to GND with a ceramic capacitor. Recommended
value is 10µF.
SW1 (Pin 10): Switching Node. External inductor con-
nects between SW1 and SW2. Recommended value is
4.7µH/5µH.
Exposed Pad (Pin 11): Ground Pin. Solder to PCB ground
for electrical contact and optimal thermal performance.
3454f
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LTC3454www.DataSheet4U.com
APPLICATIO S I FOR ATIO
VIN
VOUT
VIN
VOUT
VOLTAGE
DAC
ENx
LTC3454
ISETx
RSET ≥ RMIN
LED
ILED
=
3850
0.8V – VDAC
RSET
VDAC
VIN
(3a)
VOUT
CURRENT
DAC
ENx
LTC3454
ISETx
LED
0.8V
IDAC ≤ RMIN
ILED = 3850 • IDAC
(3b)
VIN VOUT
ENx
LTC3454
ISETx
RMIN
LED
0.8V
ILED = 3850 RMIN + RPOT
RPOT
(3c)
RSET
100
ENx
LTC3454
ISETx
RSET ≥ RMIN
VPWM
LED
ILED
=
3850
0.8V – VPWM
RSET
=
3850
0.8V
–
(DC% •
RSET
VDVCC)
DVCC
fPWM ≥ 10kHz
(3d)
3454 F03
Figure 3. Brightness control Methods: (a) Using Voltage DAC, (b) Using Current DAC, (c) Using Potentiometer, (d) Using PWM Input
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
0.675 ±0.05
R = 0.115
TYP
6
0.38 ± 0.10
10
3.50 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PIN 1
PACKAGE TOP MARK
OUTLINE (SEE NOTE 6)
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
3.00 ±0.10 1.65 ± 0.10
(4 SIDES) (2 SIDES)
0.75 ±0.05
0.00 – 0.05
(DD10) DFN 1103
51
0.25 ± 0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
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
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.
3454f
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC3454.PDF ] | |
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