LT3478/LT3478-1
4.5A Monolithic LED
Drivers with True Color
PWM Dimming
FEATURES DESCRIPTIO
True Color PWM Dimming Delivers Constant LED The LT 3478/LT3478-1 are 4.5A step-up DC/DC convert-
Color with Up to 3000:1 Range ers designed to drive LEDs with a constant current over
Wide Input Voltage Range: 2.8V to 36V a wide programmable range. Series connection of the
4.5A, 60m, 42V Internal Switch LEDs provides identical LED currents for uniform bright-
Drives LEDs in Boost, Buck-Boost or Buck Modes ness without the need for ballast resistors and expensive
Integrated Resistors for Inductor and LED Current factory calibration.
Sensing
The LT3478-1 reduces external component count and cost
Program LED Current:
by integrating the LED current sense resistor. The LT3478
100mA to 1050mA (LT3478-1)
uses an external sense resistor to extend the maximum
(10mV to 105mV)/R (LT3478)
SENSE
programmable LED current beyond 1A and also to achieve
Program LED Current De-Rating vs Temperature
greater accuracy when programming low LED currents.
Separate Inductor Supply Input
Operating frequency can be set with an external resistor
Inrush Current Protection
from 200kHz up to 2.25MHz. Unique circuitry allows a
Programmable Soft-Start
PWM dimming range up to 3000:1 while maintaining
Fixed Frequency Operation from 200kHz to 2.25MHz
constant LED color. The LT3478/LT3478-1 are ideal for
Open LED Protection (Programmable OVP)
high power LED driver applications such as automotive TFT
Accurate Shutdown/UVLO Threshold with
LCD backlights, courtesy lighting and heads-up displays.
Programmable Hysteresis
One of two CTRL pins can be used to program maximum
16-Pin Thermally Enhanced TSSOP Package
LED current. The other CTRL pin can be used to program
U
a reduction in maximum LED current vs temperature to
APPLICATIO S
maximize LED usage and improve reliability.
High Power LED Driver Additional features include inrush current protection,
Automotive Lighting programmable open LED protection and programmable
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. soft-start. Each part is available in a 16-pin thermally
All other trademarks are the property of their respective owners. Patents Pending.
enhanced TSSOP Package.
TYPICAL APPLICATIO
Automotive TFT LCD Backlight Ef ciency vs V
IN
100
10H
V 8V TO 16V
IN I = 700mA
LED
f = 500kHz
OSC
10F
4.7F PWM DUTY CYCLE = 100%
V VLSW
IN S
95
SHDN
OUT
V
REF 0.1
R
SENSE
45.3k 90
CTRL2
(LT3478)
LT3478-1 LED
OVPSET
54.9k
85
CTRL1
700mA
15W
130k
PWM SS V R
C T 6 LEDs LUXEON III (WHITE)
6 LEDs
80
(WHITE)
8 10 12 14 16
1F 0.1F 69.8k
V (V)
IN
PWM DIMMING 3478 TA01b
CONTROL
3478 TA01
34781f
1
EFFICIENCY (%)
U
ULT3478/LT3478-1
UUW
ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO
(Note 1)
TOP VIEW
SW ............................................................................42V
SW 1 16 SS
V , LED ..................................................................42V
OUT
SW 2 15 R
T
V , V , V , SHDN (Note 5) .......................................36V
IN S L
V 3 14 PWM
IN
PWM ......................................................................... 15V
V 4 13 CTRL2
S
17
CTRL1, 2 .....................................................................6V
L 5 12 CTRL1
SS, R , V , V , OVPSET ............................................2V
T C REF
V 6 11 SHDN
OUT
Operating Junction Temperature Range
LED 7 10 V
REF
(Notes 2, 3, 4) .................................... 40C to 125C
OVPSET 8 9 V
C
Storage Temperature Range ................... 65C to 150C
FE PACKAGE
16-LEAD PLASTIC TSSOP
Lead Temperature (Soldering, 10 Sec) .................. 300C
T = 125C, = 35C/W
JMAX JA
EXPOSED PAD (PIN 17) IS PGND, MUST BE SOLDERED TO PCB.
ORDER PART NUMBER FE PART MARKING
LT3478EFE 3478FE
LT3478EFE-1 3478FE-1
LT3478IFE 3478FE
LT3478IFE-1 3478FE-1
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: