LT3952
60V LED Driver with
4A Switch Current
FEATURES
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DESCRIPTION
The
LT
®
3952
is a current mode step-up DC/DC converter
with an internal, 60V, 80m DMOS power switch. The
LT3952 is specifically designed to drive high power LEDs
in multiple configurations. It combines input and output
current regulation loops with output voltage regulation to
operate as a flexible current/voltage source.
Programmable switching frequency with optional spread-
spectrum modulation provides EMI reduction, while still
allowing optimization of the external components for
efficiency or component size. The LED current is program-
mable with an external sense resistor, and can be adjusted
from zero to full scale with a voltage at the CTRL pin. The
external PWM input provides LED ON/OFF control and
4000:1 dimming ratio, and an internal PWM generator
delivers the efficiency of PWM dimming to standalone
or I/O limited applications. The LT3952 is available in the
thermally enhanced 28-lead TSSOP package.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
True Color PWM is a trademark of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents including, 7199560,
7321203, 7746300. Patents pending
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4000:1 True Color PWM™ Dimming
4A, 60V Internal DMOS Switch
Wide Input Voltage Range: 3V to 42V
0V to 60V Output Current Regulation with Monitor
PMOS Switch Driver for PWM and Output Disconnect
LED Short-Circuit Protection and
SHORTLED
Flag
Internal Spread Spectrum Frequency Modulation
Constant-Current and Constant-Voltage Regulation
Input Current Limit and Monitor
Adjustable Frequency: 200kHz to 3MHz,
Synchronizable to an External Clock
10:1 Analog Dimming
Programmable Open-LED Protection with
OPENLED
Flag
Programmable V
IN
Undervoltage and
Overvoltage Lockout
Available in a 28-Lead TSSOP Package
APPLICATIONS
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Display Backlighting
Automotive and Avionic Lighting
Accurate Current-Limited Voltage Regulators
TYPICAL APPLICATION
Short-Circuit Robust Boost LED Driver with Spread Spectrum Frequency Modulation
V
IN
7V TO 42V
4A INPUT LIMIT
10µH
15m
4.7µF
EN/UVLO
OVLO
CTRL
V
REF
PWM
ISMON
DIM
OPENLED
SHORTLED
V
C
3.6k
8.2nF
IVINCOMP
1µF
RT
90.9k
1MHz
V
IN
IVINP
IVINN
SW
GND
FB
1M
21.5k
LT3952
ISP
750m
ISN
TG
INTV
CC
SYNC/SPRD
SS
100nF
2.2µF
INTV
CC
16 LED (50V)
333mA
57V OPEN LED
REGULATION
2.2µF
100V
×2
Efficiency vs Input Voltage
100
90
EFFICIENCY (%)
80
INTV
CC
OPENLED
SHORTLED
PWM
ISMON
100k
100k
70
SSFM OFF
SSFM ON
60
0
10
20
30
V
IN
(V)
40
50
3952 TA01b
3952 TA01a
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For more information
www.linear.com/LT3952
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LT3952
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
GND
SW
SW
SW
IVINN
IVINP
V
IN
EN/UVLO
OVLO
1
2
3
4
5
6
7
8
9
29
GND
28 GND
27 ISP
26 ISN
25 TG
24 ISMON
23 IVINCOMP
22
OPENLED
21
SHORTLED
20 PWM
19 SS
18 V
REF
17 CTRL
16 FB
15 DIM
V
IN
, IVINP, IVINN,
SHORTLED, OPENLED,
EN/UVLO ..................................................................42V
OVLO ........................................................................12V
SW, ISP, ISN, TG .......................................................60V
IVINP-IVINN .....................................................–1V to 3V
CTRL, FB, DIM, SYNC/SPRD, PWM ......... INTV
CC
+ 0.3V
VC, SS, ISMON, IVINCOMP.........................................3V
RT, V
REF
.....................................................................2V
INTV
CC
(Note 4) .......................................................3.6V
Operating Junction Temperature Range (Notes 2, 3)
LT3952E/LT3952I .............................. –40°C to 125°C
LT3952H ............................................ –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
INTV
CC
10
SYNC/SPRD 11
GND 12
VC 13
RT 14
FE PACKAGE
28-LEAD PLASTIC TSSOP
θ
JA
= 30°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3952EFE#PBF
LT3952IFE#PBF
LT3952HFE#PBF
TAPE AND REEL
LT3952EFE#TRPBF
LT3952IFE#TRPBF
LT3952HFE#TRPBF
PART MARKING*
LT3952FE
LT3952FE
LT3952FE
PACKAGE DESCRIPTION
28-Lead Plastic TSSOP
28-Lead Plastic TSSOP
28-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix
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For more information
www.linear.com/LT3952
LT3952
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Operating Voltage
Supply Current
FB = 1.3V, R
T
= 40.2k, CTRL = 0V
EN/UVLO = 0V, CTRL = 0V
EN/UVLO = 1.15V, CTRL = 0V
CTRL = 0V
V
IN
= 3V, CTRL = 0V
INTV
CC
Rising, CTRL = 0V
CTRL = 0V
I
VREF
= –100 A , CTRL = 0V
3V < V
IN
< 42V , CTRL = 0V
0µA < I
VREF
< –100µA , CTRL = 0V
0.2
CTRL Falling
100
12.5
200
CTRL = 0V, Current Out of Pin
CTRL = 1.5V
ISP = 60V, CTRL = 1.5V
ISP = 60V, CTRL = 0.7V
ISP = 60V, CTRL = 0.3V
ISP = 0V, CTRL = 1.5V
CTRL = 1.5V
PWM = 5V (Active), ISP = 60V
PWM = 0V (Standby), ISP = 60V
CTRL = 0.4V, 0.8V
CTRL = 1.5V , ISP = 60V
IVINP = IVINN = 42V
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The
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denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= IVINP = IVINN = 12V, ISP = ISN = 24V, EN/UVLO = PWM = 3V, CTRL = 2V, OVLO = 0V unless otherwise noted
CONDITIONS
MIN
TYP
1.5
0
35
2.90
2.62
3.00
150
2.68
200
1.955
2.000
0.01
0.6
1.2
125
2.045
2.74
MAX
3
2.2
1
60
3.10
UNITS
V
mA
µA
µA
V
mV
V
mV
V
%/V
%
V
mV
mV
mV
100
60
250
125
25
250
375
275
250
0
4
0.950
1.000
35
55
60
1650
3
V
IVINP-IVINN
= 30mV
20
1.050
60
65
0.1
255
135
40
260
390
nA
V
mV
mV
mV
mV
mV
µS
µA
µA
V/V
V
µA
mV
µS
V
V/V
Internal Regulator
INTV
CC
Output Voltage
INTV
CC
Dropout Voltage
INTV
CC
Undervoltage Lockout
INTV
CC
UVLO Hysteresis
Reference Voltage Output
V
REF
Voltage
V
REF
Line Regulation
V
REF
Load Regulation
Current Feedback
CTRL Range for Current Sense Threshold Adjustment
CTRL PWM Shutdown Threshold
CTRL PWM Threshold Hysteresis
CTRL Zero-Scale Offset
CTRL Input Bias Current
Current Sense Common Mode Input Range
Full-Scale Current Sense Accuracy (V
ISP
-V
ISN
)
Midrange Current Sense Accuracy (V
ISP
-V
ISN
)
1/10th Scale Current Sense Accuracy (V
ISP
-V
ISN
)
Low Side Current Sense Accuracy (V
ISP
-V
ISN
)
Overcurrent Sense Threshold
ISP to VC Transconductance
ISP/ISN Input Bias Current
Current Sense Monitor Ratio (V
ISMON
)/(V
ISP
-V
ISN
)
Current Sense Monitor Accuracy (V
ISMON
)
Input Current Sense Amplifier
Amplifier Supply Current (From IVINP)
I
VIN
Regulation Threshold (V
IVINP-IVINN
)
I
VINCOMP
to VC Transconductance
Input Common Mode Minimum Voltage
IVINP/IVINN to Monitor Voltage Gain
0
245
115
10
240
350
20
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For more information
www.linear.com/LT3952
3
LT3952
The
l
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= IVINP = IVINN = 12V, ISP = ISN = 24V, EN/UVLO = PWM = 3V, CTRL = 2V, OVLO = 0V unless otherwise noted
PARAMETER
TG Gate Driver
PWM Input High Threshold
PWM Hysteresis
TG On Voltage
TG Off Voltage
TG Turn-On Time
TG Turn-Off Time
Output Voltage Feedback
FB Voltage Regulation Threshold (V
FB
)
FB Open-LED Threshold
FB Open-LED Threshold Hysteresis
FB Overvoltage Threshold
FB Overvoltage Threshold Hysteresis
FB Pin Bias Current
Feedback Line Regulation
FB to VC Transconductance
VC Output Impedance
Soft-Start
Soft-Start Sourcing Current
Soft-Start Sinking Current
Soft-Start Hiccup Retry Threshold
Soft-Start Strong Pull-Down On-Resistance
Oscillator
RT Voltage
Switching Frequency
R
T
= 470k
R
T
= 90.9k
R
T
= 40.2k
R
T
= 25.5k
R
T
= 470k
SYNC = 300kHz Clock Signal, R
T
= 470k
R
T
= 90.9k
R
T
= 40.2k
R
T
= 25.5k
180
0.95
1.90
2.75
98
97
92
85
1.20
215
1.0
2.0
3.0
99
98
95
90
80
50
75
V
SYNC
= 2V
1.5
0.4
1
31
100
250
1.05
2.10
3.25
V
kHz
MHz
MHz
MHz
%
%
%
%
%
ns
ns
k
V
V
%
%
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ELECTRICAL CHARACTERISTICS
CONDITIONS
PWM Rising
V
ISP-TG
, V
ISP
> 10V
V
ISP-TG
, PWM = 0V
C
LOAD
= 470pF, PWM Rising
C
LOAD
= 470pF, PWM Falling
CTRL = 1.5V
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MIN
1.15
TYP
1.2
20
7.5
0
100
150
MAX
1.25
9.5
0.3
UNITS
V
mV
V
V
ns
ns
1.188
1.182
V
FB
–
65mV
V
FB
+
15mV
1.200
1.200
V
FB
–
45mV
15
V
FB
+
30mV
15
20
0.0003
450
5000
1.212
1.218
V
FB
–
25mV
V
FB
+
40mV
100
V
V
V
mV
V
mV
nA
%/V
µS
k
FB Rising
FB Rising
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3V < V
IN
< 42V
Current Out of Pin, SS = 0.1V
SS = 1.8V
18
1.5
25
2.5
200
120
37
4.1
µA
µA
mV
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Maximum Duty Cycle
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Minimum Off-Time
Minimum On-Time
SYNC/SPRD Pin Resistance to GND
SYNC/SPRD Input High Threshold
SYNC/SPRD Input Low Threshold
Spread Spectrum Minimum Step as Percentage of f
SW
Spread Spectrum Maximum Step as Percentage of f
SW
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For more information
www.linear.com/LT3952
LT3952
The
l
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN
= IVINP = IVINN = 12V, ISP = ISN = 24V, EN/UVLO = PWM = 3V, CTRL = 2V, OVLO = 0V unless otherwise noted
PARAMETER
PWM Generator
PWM Pin Pull-Up/Pull-Down Current
PWM Generator Lower Threshold Offset
PWM Generator Upper Threshold Offset
PWM Generator Frequency
DIM Pin Output Current
TG Duty Cycle Using PWM Generator
PWM = 1.2V, DIM = 0.7V
0.2V < DIM < 1.2V
0.2V < DIM < 1.2V
DIM = 0.7V, C
PWM
= 22nF
DIM = 0.7V
DIM = 0.345V
DIM = 0.535V
DIM = 0.725V
DIM = 1.105V
I
SW
= 500mA
SW = 60V, CTRL = 0V
7.5
VC = 2V
EN/UVLO Falling
EN/UVLO = 1.25V, Device in Shutdown
EN/UVLO = 1.5V, Device in Operation
OVLO Rising
OVLO = 1V
I
SHORTLED
= 1mA
I
SHORTLED
= 2mA
SHORTLED
= 42V
I
OPENLED
= 1mA
I
OPENLED
= 2mA
OPENLED
= 42V
60
0.3
1
V
µA
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
5
V
DIM
+
825
10
1
21
42.5
86
TYP
10
V
DIM
+
950
230
20
10
30
50
90
80
MAX
15
V
DIM
+
1075
30
21
39
57.5
94
UNITS
µA
mV
mV
Hz
µA
%
%
%
%
m
V
DIM
– 15 V
DIM
+ 0 V
DIM
+ 15
Power Switch
Switch On-Resistance
Switch Leakage Current
VC to Current Threshold Transconductance
Maximum Power Switch Current Limit
Logic Inputs/Outputs
EN/UVLO Disable Threshold
EN/UVLO Threshold Internal Hysteresis
EN/UVLO Hysteresis Current
OVLO Threshold
OVLO Threshold Hysteresis
OVLO Input Bias Current
SHORTLED
On-Resistance
SHORTLED
Output Low Voltage
SHORTLED
Off-State Leakage
OPENLED
On-Resistance
OPENLED
Output Low Voltage
OPENLED
Off-State Leakage
1.191
1.230
75
2
0
1.191
1.230
25
15
60
0.3
1
V
µA
100
0.4
1.269
1.269
V
mV
µA
µA
V
mV
nA
4
2
4.5
5
µA
S
A
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:
The LT3952E is guaranteed to meet specified performance from
0°C to 125°C. Specifications over the –40°C to 125°C operating junction
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3952I is guaranteed to meet
performance specifications over the –40°C to 125°C operating junction
temperature range. The LT3952H is guaranteed to meet performance
specifications over the full –40°C to 150°C operating junction temperature
range. High junction temperatures degrade operating lifetimes. Operating
lifetime is derated at junction temperatures greater than 125°C.
Note 3:
The LT3952 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature is active. Continuous operating above the specified
maximum operating junction temperature may impair device reliability.
Note 4:
INTV
CC
is an output and is not meant to be externally driven.
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For more information
www.linear.com/LT3952
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