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LT3474EFE-1#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LT3474/LT3474-1
1
3474fd
The LT
®
3474/LT3474-1 are fi xed frequency step-down
DC/DC converters designed to operate as constant-current
sources. An internal sense resistor monitors the output
current allowing accurate current regulation, ideal for
driving high current LEDs. High output current accuracy
is maintained over a wide current range, from 35mA to
1A, allowing a wide dimming range.
Unique PWM circuitry allows a dimming range of 400:1,
avoiding the color shift normally associated with LED
current dimming.
The high switching frequency offers several advantages,
permitting the use of small inductors and ceramic capaci-
tors. Small inductors combined with the 16-lead TSSOP
surface mount package save space and cost versus
alternative solutions. The constant switching frequency
combined with low-impedance ceramic capacitors result
in low, predictable output ripple.
With their wide input range of 4V to 36V, the LT3474/
LT3474-1 regulate a broad array of power sources, from
5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. A current mode
PWM architecture provides fast transient response and
cycle-by-cycle current limiting. Frequency foldback and
thermal shutdown provide additional protection.
■
Automotive and Avionic Lighting
■
Architectural Detail Lighting
■
Display Backlighting
■
Constant Current Sources
n
True Color PWM™ Delivers Constant Color with
400:1 Dimming Range
n
Wide Input Range: 4V to 36V
n
Up to 1A LED Current
n
Adjustable 200kHz–2MHz Switching Frequency
n
Adjustable Control of LED Current
n
Integrated Boost Diode
n
High Output Current Accuracy is Maintained
Over a Wide Range from 35mA to 1A
n
Open LED (LT3474) and Short-Circuit Protection
n
High Side Sense Allows Grounded
Cathode Connection
n
Uses Small Inductors and Ceramic Capacitors
n
LT3474-1 Drives LED Strings Up to 26V
n
Compact 16-Lead TSSOP Thermally Enhanced
Surface Mount Package
TYPICAL APPLICATION
DESCRIPTION
Step-Down
1A LED Driver
Step-Down 1A LED Driver
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners. Patent Pending
FEATURES
APPLICATIONS
Effi ciency
V
IN
BIAS
OUT
PWM
LED
LED1
DIMMING*
CONTROL
LT3474
0.1μF
V
IN
5V TO 36V
2.2μF
0.22μF
10μH
3474 TA01a
80.6k
*SEE APPLICATIONS SECTION FOR DETAILS
SHDN
REF
BOOST
SW
V
ADJ
R
T
V
C
GND
2.2μF
LED CURRENT (mA)
0
EFFICIENCY (%)
70
75
80
600
1000
3474 G02
65
60
55
200 400 800
85
90
95
TWO SERIES CONNECTED
WHITE 1A LEDS
ONE WHITE 1A LED
V
IN
= 12V
LT3474/LT3474-1
2
3474fd
PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS
V
IN
Pin ........................................................(–0.3V), 36V
BIAS Pin ....................................................................25V
BOOST Pin Voltage ...................................................51V
BOOST above SW Pin ...............................................25V
OUT, LED Pins (LT3474) ............................................15V
OUT, LED Pins (LT3474-1) .........................................26V
PWM Pin ...................................................................10V
V
ADJ
Pin .....................................................................6V
V
C
, REF, R
T
Pins ..........................................................3V
SHDN Pin ...................................................................V
IN
BIAS Pin Current .........................................................1A
Maximum Junction Temperature (Note 2)............. 125°C
Operating Temperature Range (Note 3)
LT3474E, LT3474E-1 ............................ –40°C to 85°C
LT3474I, LT3474I-1 ............................ –40°C to 125°C
Storage Temperature Range ................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
(Note 1)
FE PACKAGE
16-LEAD PLASTIC TSSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
DNC*
OUT
LED
V
IN
SW
BOOST
BIAS
GND
DNC*
GND
PWM
V
ADJ
V
C
REF
SHDN
R
T
17
θ
JC
= 8°C/W, θ
JA
= 40°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
*DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS.
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3474EFE#PBF LT3474EFE#TRPBF 3474EFE 16-Lead TSSOP –40°C to 85°C
LT3474IFE#PBF LT3474IFE#TRPBF 3474IFE 16-Lead TSSOP –40°C to 125°C
LT3474EFE-1#PBF LT3474EFE-1#TRPBF 3474EFE-1 16-Lead TSSOP –40°C to 85°C
LT3474IFE-1#PBF LT3474IFE-1#TRPBF 3474IFE-1 16-Lead TSSOP –40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to:
http://www.linear.com/tapeandreel/
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage
l
3.5 4 V
Input Quiescent Current Not Switching 2.6 4 mA
Shutdown Current SHDN = 0.3V, V
BOOST
= 0V, V
OUT
= 0V 0.01 2 μA
LED Pin Current V
ADJ
Tied to V
REF
V
ADJ
Tied to V
REF
/5
l
l
0.98
0.968
0.193
0.186
1
0.2
1.02
1.025
0.207
0.210
A
A
A
A
REF Voltage
l
1.23 1.25 1.265 V
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 12V, V
BOOST
= 16V, V
OUT
= 4V unless otherwise noted (Note 3).
LT3474/LT3474-1
3
3474fd
ELECTRICAL CHARACTERISTICS
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may impair device reliability.
Note 3: The LT3474E and LT3474E-1 are guaranteed to meet performance
specifi cations from 0°C to 70°C. Specifi cations over the –40°C to 85°C
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 12V, V
BOOST
= 16V, V
OUT
= 4V unless otherwise noted (Note 3).
PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Voltage Line Regulation 5V < V
IN
< 36V 0.01 %/V
Reference Voltage Load Regulation 0 < I
REF
< 250μA 0.0002 %/μA
V
ADJ
Pin Bias Current (Note 4)
l
20 400 nA
Switching Frequency R
T
= 80.6k
l
470
450
500 530
540
kHz
kHz
Maximum Duty Cycle R
T
= 80.6k
R
T
= 10k
R
T
= 232k
l
90 95
76
98
%
%
%
Foldback Frequency R
T
= 80.6k, V
OUT
= 0V 70 kHz
SHDN Threshold (to Switch) 2.6 2.65 2.7 V
SHDN Pin Current (Note 5) V
SHDN
= SHDN Threshold 8.3 10.3 12.3 μA
PWM Threshold 0.4 0.9 1.2 V
V
C
Switching Threshold 0.8 V
V
C
Source Current V
C
= 1V 100 μA
V
C
Sink Current V
C
= 1V 100 μA
LED to V
C
Current Gain 1.5 μA/mA
LED to V
C
Transresistance 1 V/mA
V
C
to Switch Current Gain 2A/V
V
C
Clamp Voltage 1.9 V
V
C
Pin Current in PWM Mode V
C
= 1V, V
PWM
= 0.3V
l
0.01 1 μA
OUT Pin Clamp Voltage (LT3474) 13.2 13.8 14.5 V
OUT Pin Current in PWM Mode V
OUT
= 4V, V
PWM
= 0.3V
l
0.1 10 μA
Switch Current Limit (Note 6) –40°C to 85°C
LT3474I, LT3474I-1 at 125°C
l
1.6
1.5
2.1 3.2
3.2
A
A
Switch V
CESAT
I
SW
= 1A 380 500 mV
Boost Pin Current I
SW
= 1A 30 50 mA
Switch Leakage Current 0.01 1 μA
Minimum Boost Voltage (Note 7) 1.9 2.5 V
Boost Diode Forward Voltage I
DIO
= 100mA 600 mV
operating temperature range are assured by design, characterization and
correlation with statistical process controls. The LT3474I and LT3474I-1
are guaranteed to meet performance specifi cations over the –40°C to
125°C operating temperature range.
Note 4: Current fl ows out of pin.
Note 5: Current fl ows into pin.
Note 6: Current limit is guaranteed by design and/or correlation to static
test. Slope compensation reduces current limit at higher duty cycles.
Note 7: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LT3474EFE-1#TRPBF

Mfr. #:
Buy LT3474EFE-1#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
LED Lighting Drivers 1A Step Down LED Driver in TSSOP-16E
Lifecycle:
New from this manufacturer.
Delivery:
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