LT3795
110V LED Controller with
Spread Spectrum Frequency Modulation
FeaTures
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DescripTion
The
LT
®
3795
is a DC/DC controller designed to regulate a
constant-current or constant-voltage and is ideal for driv-
ing LEDs. It drives a low side external N-channel power
MOSFET from an internal regulated 7.7V supply. The fixed
frequency and current mode architecture result in stable
operation over a wide range of supply and output voltages.
Spread spectrum frequency modulation (SSFM) can be
activated for improved electromagnetic compatibility (EMC)
performance. The ground referred voltage FB pin serves as
the input for several LED protection features, and also al-
lows the converter to operate as a constant-voltage source.
The maximum output current is set by an external resistor,
and the output current amplifier has a rail-to-rail common
mode range. The LT3795 also includes a separate input
current sensing amplifier that is used to limit input current.
The TG pin inverts and level shifts the PWM signal to drive
the gate of the external PMOS. The PWM input provides
LED dimming ratios of up to 3000:1, and the CTRL inputs
provide additional analog dimming capability.
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.
3000:1 True Color PWM™ Dimming
Wide Input Voltage Range: 4.5V to 110V
Input and Output Current Reporting
PMOS Switch Driver for PWM and Output Disconnect
Internal Spread Spectrum Frequency Modulation
±2% Constant Voltage Regulation
±3% Constant Current Regulation: 0V ≤ V
OUT
≤ 110V
Programmable Input Current limit
CTRL Inputs Linearly Adjust LED Current
Adjustable Frequency: 100kHz to 1MHz
Programmable Open LED Protection with
OPENLED
Flag
Short-Circuit Protection and
SHORTLED
Flag
Programmable Undervoltage Lockout with Hysteresis
Soft-Start with Programmable Fault Restart Timer
C/10 Detection for Battery Charging
Available in 28-Lead TSSOP Package
applicaTions
n
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High Power LED, High Voltage LED
Battery Chargers
Accurate Current Limited Voltage Regulators
Typical applicaTion
Short-Circuit Robust Boost LED Driver with Spread Spectrum Frequency Modulation
V
IN
8V TO 60V
110V (TRANSIENT)
63V OVLO
15m
2.2µF
×3
499k
115k
12.4k
CTRL1
CTRL2
V
REF
PWM
10nF
INTV
CC
100k
OPENLED
SHORTLED
100k
OPENLED
SHORTLED
V
C
RT
10k
6.8nF
3795 TA01a
Efficiency vs V
IN
100
22µH
1M
2.2µF
×4
95
EFFICIENCY (%)
90
85
80
75
EN/UVLO V
IN
OVLO
IVINP
IVINN
GATE
SENSE
15m
13.3k
LT3795
GND
FB
ISP
620m
ISN
TG
INTV
CC
INTV
CC
4.7µF
0.1µF
87V LED
400mA
PWM
IVINCOMP
RAMP
6.8nF
70
0
10
20
30
V
IN
(V)
40
50
60
3795 TA01b
ISMON
0.1µF
SS
31.6k
250kHz
3795fb
For more information
www.linear.com/LT3795
1
LT3795
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
ISP
ISN
TG
GND
ISMON
CTRL2
FB
V
C
CTRL1
1
2
3
4
5
6
7
8
9
29
GND
28 IVINCOMP
27 IVINP
26 IVINN
25 OVLO
24 EN/UVLO
23 V
IN
22 GND
21 GND
20 INTV
CC
19 GATE
18 SENSE
17 GND
16
OPENLED
15
SHORTLED
V
IN
.......................................................................... 110V
EN/UVLO ................................................................. 110V
ISP, ISN ................................................................... 110V
TG, GATE...............................................................Note 2
IVINP, IVINN ............................................................ 110V
V
IN
- IVINN ................................................... –0.3V to 4V
INTV
CC
(Note 3) .....................................8.6V, V
IN
+ 0.3V
PWM,
SHORTLED, OPENLED
.....................................12V
FB, RAMP, OVLO .........................................................8V
CTRL1, CTRL2...........................................................15V
SENSE ......................................................................0.5V
ISMON, IVINCOMP .....................................................5V
V
C
, V
REF
, SS ................................................................3V
RT ...............................................................................2V
Operating Junction Temperature Range (Note 4)
LT3795E/LT3795I .................................. –40 to 125°C
LT3795H ................................................ –40 to 150°C
Storage Temperature Range ......................–65 to 150°C
V
REF
10
SS 11
RT 12
RAMP 13
PWM 14
FE PACKAGE
28-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 30°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LT3795EFE#PBF
LT3795IFE#PBF
LT3795HFE#PBF
TAPE AND REEL
LT3795EFE#TRPBF
LT3795IFE#TRPBF
LT3795HFE#TRPBF
PART MARKING*
LT3795FE
LT3795FE
LT3795FE
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.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
elecTrical characTerisTics
PARAMETER
V
IN
Minimum Operating Voltage
V
IN
Shutdown I
Q
V
IN
Operating I
Q
(Not Switching)
V
REF
Voltage
V
REF
Pin Line Regulation
V
REF
Pin Load Regulation
SENSE Current Limit Threshold
CONDITIONS
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
IN
= 24V, EN/UVLO = 24V, CTRL1 = CTRL2 = 2V, PWM = 5V, unless otherwise noted.
MIN
TYP
MAX
4.5
10
22
2.9
l
UNITS
V
µA
µA
mA
V
m%/V
m%/µA
V
IN
Tied to INTV
CC
EN/UVLO = 0V, PWM = 0V
EN/UVLO = 1.15V, PWM = 0V
R
T
= 82.5k to GND, FB = 1.5V
–100µA ≤ I
REF
≤ 10µA
4.5V < V
IN
< 110V
–100µA ≤ I
REF
≤ 0µA
l
3.5
2.06
1.97
2.015
1.5
10
100
117
125
mV
3795fb
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For more information
www.linear.com/LT3795
LT3795
elecTrical characTerisTics
PARAMETER
SENSE Input Bias Current
SS Sourcing Current
SS Sinking Current
Error Amplifier
Full Scale LED Current Sense Threshold
(V
(ISP-ISN)
)
9/10th LED Current Sense Threshold
(V
(ISP-ISN)
)
1/2 LED Current Sense Threshold
(V
(ISP-ISN)
)
1/10th LED Current Sense Threshold
(V
(ISP-ISN)
)
ISP/ISN Current Monitor Voltage (V
ISMON
)
ISP/ISN Overcurrent Protection Threshold
(V
(ISP-ISN)
)
CTRL1, CTRL2 Input Bias Current
ISP/ISN Current Sense Amplifier Input
Common Mode Range
ISP/ISN Input Current Bias Current
(Combined)
ISP/ISN Current Sense Amplifier g
m
V
C
Output Impedance
V
C
Standby Input Bias Current
FB Regulation Voltage (V
FB
)
FB Amplifier g
m
FB Pin Input Bias Current
FB Open LED Threshold
C/10 Comparator Threshold (V
(ISP-ISN)
)
FB Overvoltage Threshold
V
C
Current Mode Gain (∆V
VC
/∆V
SENSE
)
FB
SHORTLED
Threshold
V
C
Pin Source Current
V
C
Pin Sink Current
Input Current Sense Amplifier
Input Current Sense Amplifier Input Voltage
Common Range (V
IVINP
/V
IVINN
)
Input Current Sense Threshold
(V
IVINP
- V
IVINN
)
Input Current Monitor V(IVINCOMP)
Input Bias Current (I(IVINN))
Input Current Sense Amplifier g
m
V
IVINP
= 48V, V
IN
= 48V
V
IVINP
-V
IVINN
= 50mV, V
IN
= 48V
V
IVINP
-V
IVINN
= 50mV, V
IN
= 48V
V
IVINP
-V
IVINN
= 60mV, V
IN
= 48V
l
l
l
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
IN
= 24V, EN/UVLO = 24V, CTRL1 = CTRL2 = 2V, PWM = 5V, unless otherwise noted.
CONDITIONS
Current Out of Pin
SS = 0V
ISP – ISN = 1V, SS = 2V
ISP = 48V, CTRL1 ≥ 1.2V, CTRL2 ≥ 1.2V
ISP = 0V, CTRL1 ≥ 1.2V, CTRL2 ≥ 1.2V
ISP = 48V, CTRL1 = 1V, CTRL2 = 1.2V
ISP = 0V, CTRL1 = 1V, CTRL2 = 1.2V
ISP = 48V, CTRL1 = 0.6V, CTRL2 = 1.2V
ISP = 0V, CTRL1 = 0.6V, CTRL2 = 1.2V
ISP = 48V, CTRL1 = 0.2V, CTRL2 = 1.2V
ISP = 0V, CTRL1 = 0.2V, CTRL2 = 1.2V
V
(ISP-ISN)
= 250mV, ISP = 48V, –50µA ≤ I
ISMON
≤ 0 µA
V
(ISP-ISN)
= 250mV, ISP = 0V, –50µA ≤ I
ISMON
≤ 0 µA
ISN = 48V
ISN = 0V
Current Out of Pin, CTRL = 1V
0
PWM = 5V (Active), ISP = 48V
PWM = 0V (Standby), ISP = 48V
V
(ISP-ISN)
= 250mV
PWM = 0V
ISP = ISN = 48V
ISP = ISN = 48V
Current Out of Pin, FB = V
FB
OPENLED
Falling, ISP = ISN = 48V
OPENLED
Falling, FB = 1.25V, ISP = 48V
OPENLED
Falling, FB = 1.25V, ISN = 0V
TG Rising
SHORTLED
Falling
V
C
= 1.2V
V
C
= 1.2V, FB = 1.4V
2.5
57
0.94
60
1
100
3400
1
15
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MIN
TYP
65
28
2.8
MAX
UNITS
µA
µA
µA
243
243
220
220
119
119
16
16
0.96
0.96
360
360
250
250
225
225
125
125
25
25
1
1
375
375
50
257
257
230
230
130
130
32
32
1.04
1.04
390
390
200
110
mV
mV
mV
mV
mV
mV
mV
mV
V
V
mV
mV
nA
V
µA
µA
µS
kΩ
700
0
350
2000
–20
1.230
1.238
1.250
1.250
600
40
25
25
0.1
20
1.270
1.264
200
nA
V
V
µS
nA
V
mV
mV
V
V/V
mV
µA
µA
V
FB
– 62mV V
FB
– 52mV V
FB
– 42mV
V
FB
+ 35mV V
FB
+ 50mV V
FB
+ 60mV
4.2
300
10
30
110
63
1.06
1000
350
V
mV
V
nA
µS
µs
kΩ
3795fb
Input Step Response (to 50% of Output Step) ∆V
SENSE
= 60mV Step, V
IN
= 48V
IVINCOMP Pin Resistance to GND
V
IN
= 48V
For more information
www.linear.com/LT3795
3
LT3795
elecTrical characTerisTics
PARAMETER
Linear Regulator
INTV
CC
Regulation Voltage
Dropout (V
IN
-INTV
CC
)
INTV
CC
Current Limit
INTV
CC
Shutdown Bias Current if Externally
Driven to 7V
INTV
CC
Undervoltage Lockout
INTV
CC
Undervoltage Lockout Hysteresis
Oscillator
Switching Frequency
R
T
= 82.5k
R
T
= 19.6k
R
T
= 6.65k
(Note 5)
(Note 5)
V
RAMP
= 2V
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l
l
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
IN
= 24V, EN/UVLO = 24V, CTRL1 = CTRL2 = 2V, PWM = 5V, unless otherwise noted.
CONDITIONS
MIN
7.4
18
85
13
3.8
4
200
85
340
900
105
400
1000
160
210
70
1
2
RAMP = 0.4V
RAMP = 1.6V
l
TYP
7.7
550
MAX
8
UNITS
V
mV
mA
mA
I
INTVCC
= –10mA, V
IN
= 4.5V
V
IN
= 110V, INTV
CC
= 6V
V
IN
= 12V, INTV
CC
= 6V
EN/UVLO = 0V, INTV
CC
= 7V
17
4.1
µA
V
mV
125
480
1150
kHz
kHz
kHz
ns
ns
%
V
V
µA
µA
Minimum Off-Time
Minimum On-Time
Switching Frequency Modulation
RAMP Input Low Threshold
RAMP Input High Threshold
RAMP Pin Source Current
RAMP Pin Sink Current
LOGIC Input/Outputs
PWM Input Threshold Rising
PWM Pin Bias Current
EN/UVLO Threshold Voltage Falling
EN/UVLO Rising Hysteresis
EN/UVLO Input Low Voltage
EN/UVLO Pin Bias Current Low
EN/UVLO Pin Bias Current High
OPENLED
OUTPUT Low
SHORTLED
OUTPUT Low
OVLO Threshold Voltage Rising
OVLO Falling Hysteresis
OVLO Pin Input Current
Gate Driver
t
r
NMOS GATE Driver Output Rise Time
t
f
NMOS GATE Driver Output Fall Time
NMOS GATE Output Low (V
OL
)
NMOS GATE Output High (V
OH
)
t
r
Top GATE Driver Output Rise Time
t
f
Top GATE Driver Output Fall Time
Top Gate On Voltage (V
ISP
-V
TG
)
Top Gate Off Voltage (V
ISP
-V
TG
)
12
12
0.96
1.185
0.4
2.5
3
10
3.8
100
300
300
l
1
10
1.220
20
1.04
1.25
V
µA
V
mV
V
µA
nA
mV
mV
V
mV
nA
ns
ns
l
I
VIN
Drops Below 10µA
EN/UVLO = 1.15V
EN/UVLO = 1.30V
I
OPENLED
= 0.5mA
I
SHORTLED
= 0.5mA
1.215
1.25
28
150
1.28
C
L
= 3300pF, 10% to 90%
C
L
= 3300pF, 10% to 90%
INTV
CC
–
0.05
C
L
= 300pF
C
L
= 300pF
ISP = 48V
PWM = 0V, ISP = 48V
20
18
0.05
V
V
50
100
7
0
8
0.3
ns
ns
V
V
3795fb
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For more information
www.linear.com/LT3795
LT3795
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:
Do not apply a positive or negative voltage source to TG and GATE
pins, otherwise permanent damage may occur.
Note 3:
Operating maximum for INTV
CC
is 8V.
Note 4:
The LT3795E 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 LT3795I is guaranteed to meet
performance specifications over the –40°C to 125°C operating junction
temperature range. The LT3795H is guaranteed 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 5:
See Duty Cycle Considerations in the Applications Information
section.
Typical perForMance characTerisTics
300
250
200
150
100
50
0
T
A
= 25°C, unless otherwise noted.
V
(ISP-ISN)
Full-Scale Threshold
vs Temperature
254
253
V
(ISP-ISN)
THRESHOLD (mV)
252
251
250
249
248
247
ISP = 48V
CTRL1= CTRL2 = 2V
V
(ISP-ISN)
Threshold vs V
CTRL
253
252
251
250
249
248
247
V
(ISP-ISN)
Threshold vs V
ISP
V
(ISP-ISN)
THRESHOLD (mV)
V
(ISP-ISN)
THRESHOLD (mV)
0
0.2
0.4
0.6 0.8
V
CTRL
(V)
1.0
1.2
1.4
0
20
40
60
V
ISP
(V)
80
100
120
3795 G02
246
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3795 G03
3795 G01
V
(ISP-ISN)
Threshold at CTRL1 = 0.6V,
CTRL2 = 1.2V vs Temperature
128
127
126
125
124
123
122
–50 –25
300
250
V
(ISP-ISN)
Threshold vs FB Voltage
1.27
V
FB
vs Temperature
V
(ISP-ISN)
THRESHOLD (mV)
1.26
200
150
100
1.24
50
0
1.1
1.23
–50 –25
V
FB
(V)
1.15
1.2
V
FB
(V)
1.25
1.3
3795 G04
V
(ISP-ISN)
(mV)
1.25
0
25
50
75
100 125 150
3795 G03a
0
25
50
75
100 125 150
3795 G05
TEMPERATURE (°C)
TEMPERATURE (°C)
3795fb
For more information
www.linear.com/LT3795
5
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