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LT3475IFE#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LT3475/LT3475-1
1
3475fb
Dual Step-Down
1.5A LED Driver
The LT
®
3475/LT3475-1 are dual step-down DC/DC
converters designed to operate as a constant-current
source. An internal sense resistor monitors the output
current allowing accurate current regulation ideal for
driving high current LEDs. The high side current sense al-
lows grounded cathode LED operation. High output current
accuracy is maintained over a wide current range, from
50mA to 1.5A, allowing a wide dimming range. Unique
PWM circuitry allows a dimming range of 3000:1, avoid-
ing 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 20 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 its wide input range of 4V to 36V, the LT3475/LT3475-1
regulate a broad array of power sources. 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
■
True Color PWM
TM
Delivers Constant Color with
3000:1 Dimming Range
■
Wide Input Range: 4V to 36V Operating, 40V
Maximum
■
Accurate and Adjustable Control of LED Current
from 50mA to 1.5A
■
High Side Current Sense Allows Grounded Cathode
LED Operation
■
Open LED (LT3475) and Short Circuit Protection
■
LT3475-1 Drives LED Strings Up to 25V
■
Accurate and Adjustable 200kHz to 2MHz
Switching Frequency
■
Anti-Phase Switching Reduces Ripple
■
Uses Small Inductors and Ceramic Capacitors
■
Available in the Compact 20-Lead TSSOP Thermally
Enhanced Surface Mount Package
Dual Step-Down 1.5A LED Driver
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
Effi ciency
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patents Pending.
BOOST1 BOOST2
SW1 SW2
OUT1 OUT2
LED1 LED2
PWM1 PWM2
V
C1
V
C2
REF R
T
V
ADJ1
V
ADJ2
GND
LT3475
V
IN
V
IN
5V TO 36V
SHDN
0.22μF
4.7μF
10μH 10μH
0.22μF
24.3k
2.2μF
2.2μF
DIMMING*
CONTROL
*DIMMING
CONTROL
0.1μF
0.1μF
3475 TA01
1.5A LED
CURRENT
1.5A LED
CURRENT
f
SW
= 600kHz*SEE APPLICATIONS SECTION FOR DETAILS
LED CURRENT (A)
0
EFFICIENCY (%)
70
75
80
3475 TA01b
65
60
55
0.5 1
85
90
95
1.5
TWO SERIES CONNECTED
WHITE 1.5A LEDS
SINGLE WHITE 1.5A LED
V
IN
= 12V
LT3475/LT3475-1
2
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V
IN
Pin .........................................................(-0.3V), 40V
BOOST Pin Voltage ...................................................60V
BOOST Above SW Pin ...............................................30V
OUT, LED, Pins (LT3475) ...........................................15V
OUT, LED Pins (LT3475-1) .........................................25V
PWM Pin ...................................................................15V
V
ADJ
Pin ......................................................................6V
V
C
, R
T
, REF Pins ..........................................................3V
SHDN Pin ...................................................................V
IN
Maximum Junction Temperature (Note 2)............. 125°C
Operating Temperature Range (Note 3)
LT3475E/LT3475E-1 ............................. –40°C to 85°C
LT3475I/LT3475I-1 ............................. –40°C to 125°C
Storage Temperature Range ................... –65°C to 150°C
Lead Temperature Range (Soldering, 10 sec) ....... 300°C
(Note 1)
The
● 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
Minimum Input Voltage
●
3.7 4 V
Input Quiescent Current Not Switching 6 8 mA
Shutdown Current
SHDN = 0.3V, V
BOOST
= V
OUT
= 0V
0.01 2 μA
ELECTRICAL CHARACTERISTICS
ABSOLUTE AXI U RATI GS
W
WW
U
FE PACKAGE
20-LEAD PLASTIC TSSOP
1
2
3
4
5
6
7
8
9
10
TOP VIEW
20
19
18
17
16
15
14
13
12
11
OUT1
LED1
BOOST1
SW1
V
IN
V
IN
SW2
BOOST2
LED2
OUT2
PWM1
V
ADJ1
V
C1
REF
SHDN
GND
R
T
V
C2
V
ADJ2
PWM2
21
T
JMAX
= 125°C, θ
JA
= 30°C/W, θ
JC
= 8°C/W
EXPOSED PAD (PIN 21) IS GROUND AND MUST
BE ELECTRICALLY CONNECTED TO THE PCB.
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3475EFE#PBF LT3475EFE#TRPBF LT3475EFE 20-Lead Plastic TSSOP –40°C to 85°C
LT3475IFE#PBF LT3475IFE#TRPBF LT3475IFE 20-Lead Plastic TSSOP –40°C to 125°C
LT3475EFE-1#PBF LT3475EFE-1#TRPBF LT3475FE-1 20-Lead Plastic TSSOP –40°C to 85°C
LT3475IFE-1#PBF LT3475IFE-1#TRPBF LT3475FE-1 20-Lead Plastic TSSOP –40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
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/
PIN CONFIGURATION
ORDER INFORMATION
LT3475/LT3475-1
3
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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 LT3475E and LT3475E-1 are guaranteed to meet performance
specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls. The LT3475I and LT3475I-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.
The ● 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
LED Pin Current V
ADJ
Tied to V
REF
• 2/3
V
ADJ
Tied to V
REF
• 7/30
LT3475E/LT3475E-1 0°C to 85°C
●
●
0.97
0.94
0.336
0.325
0.31
1.00
0.350
1.03
1.04
0.364
0.375
0.385
A
A
A
A
A
REF Voltage
●
1.22 1.25 1.27 V
Reference Voltage Line Regulation 4V < V
IN
< 40V 0.05 %/V
Reference Voltage Load Regulation 0 < I
REF
< 500μA 0.0002 %/μA
V
ADJ
Pin Bias Current (Note 4)
●
40 400 nA
Switching Frequency R
T
= 24.3k
●
530 600 640 kHz
Maximum Duty Cycle R
T
= 24.3k
R
T
= 4.32k
R
T
= 100k
●
90 95
80
98
%
%
%
Switching Phase R
T
= 24.3k 150 180 210 Deg
Foldback Frequency R
T
= 24.3k, V
OUT
= 0V 80 kHz
SHDN
Threshold (to Switch) 2.5 2.6 2.74 V
SHDN
Pin Current (Note 5) V
SHDN
=
2.6V
7911 μA
PWM Threshold 0.3 0.8 1.2 V
V
C
Switching Threshold 0.8 V
V
C
Source Current V
C
= 1V 50 μA
V
C
Sink Current V
C
= 1V 50 μA
LED to V
C
Transresistance 500 V/A
LED to V
C
Current Gain 1 mA/μA
V
C
to Switch Current Gain 2.6 A/V
V
C
Clamp Voltage 1.8 V
V
C
Pin Current in PWM Mode V
C
= 1V, V
PWM
= 0.3V
●
10 400 nA
OUT Pin Clamp Voltage (LT3475) 13.5 14 14.5 V
OUT Pin Current in PWM Mode V
OUT
= 4V, V
PWM
= 0.3V
●
25 50 μA
Switch Current Limit (Note 6) 2.3 2.7 3.2 A
Switch V
CESAT
I
SW
=1.5A 350 500 mV
BOOST Pin Current I
SW
=1.5A 25 40 mA
Switch Leakage Current 0.1 10 μA
Minimum Boost Voltage Above SW 1.8 2.5 V
ELECTRICAL CHARACTERISTICS
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LT3475IFE#TRPBF

Mfr. #:
Buy LT3475IFE#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
LED Lighting Drivers Dual Step-Down 1.5A LED Driver
Lifecycle:
New from this manufacturer.
Delivery:
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