FeaTures
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LT3796/LT3796-1
100V Constant-Current and
Constant-Voltage Controller
with Dual Current Sense
DescripTion
The
LT
®
3796/LT3796-1
are DC/DC controllers designed to
regulate a constant-current or constant-voltage and are
ideal for driving LEDs. The fixed frequency and current
mode architecture result in stable operation over a wide
range of supply and output voltages. Two ground referred
voltage FB pins serve as the input for several LED protec-
tion features, and also allow the converter to operate as a
constant-voltage source. The LT3796/LT3796-1 feature a
programmable threshold output current sense amplifier
with rail-to-rail common mode range. A separate high
side amplifier is gain configurable with two resistors and
can be used to regulate a second current or a voltage
in combination with one of the FB pins. The PWM input
provides LED dimming ratios of up to 3000:1.
The LT3796-1 is optimized for a second output current
regulation loop that can be enabled/disabled with a PMOS
switch, either to drive a second LED string or to extend
analog dimming range.
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: 6V to 100V
Current Monitoring Up to 100V
High Side PMOS Disconnect and PWM Switch Driver
Constant-Current and Constant-Voltage Regulation
Dual Current Sense Amplifiers with Reporting
C/10 Detection for Battery and SuperCap Charging
Linear Current Sense Threshold Programming
Short-Circuit Protection
Adjustable Frequency: 100kHz to 1MHz
Frequency Synchronization (LT3796)
Independent Top Gate Enable Pin (LT3796-1)
Programmable Open LED Protection with
VMODE
Flag
Programmable Undervoltage Lockout with Hysteresis
Soft-Start with Programmable Fault Restart Timer
Available in 28-Lead TSSOP Package
applicaTions
n
n
n
High Power LED, High Voltage LED, Dual String
Battery and SuperCap Chargers
Accurate Current Limited Voltage Regulators
Typical applicaTion
Boost LED Driver with Input Current Monitor
V
IN
9V TO 60V
100V (TRANSIENT)
2.2µF
×3
1M
499k
V
IN
118k
97.6k
EN/UVLO
V
REF
CTRL
CSOUT
10nF
40.2k
PWM
0.1µF
100k
FAULT
VMODE
100k
FAULT
VMODE
V
C
10nF
10k
RT
FB2
31.6k
250kHz
CSOUT
PWM
ISMON
SYNC
LT3796
V
S
50m
22µH
2.2µF
×4
100
1M
CSN
GATE
SENSE
15m
GND
FB1
ISP
620m
ISN
TG
INTV
CC
SS
0.1µF
INTV
CC
4.7µF
85V LED
400mA
75
70
13.7k
95
EFFICIENCY (%)
90
85
80
Efficiency vs V
IN
2k
CSP
0
10
20
INTV
CC
30
V
IN
(V)
40
50
60
37961 TA01b
37961 TA01a
3796fb
For more information
www.linear.com/3796
1
LT3796/LT3796-1
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
ISP
ISN
TG
GND
ISMON
FB2
FB1
V
C
CTRL
1
2
3
4
5
6
7
8
9
29
GND
28 CSOUT
27 CSP
26 CSN
25 V
S
24 EN/UVLO
23 V
IN
22 GND
21 GND
20 INTV
CC
19 GATE
18 SENSE
17 GND
16
VMODE
15
FAULT
V
IN
, V
S
....................................................................100V
EN/UVLO .................................................................100V
ISP, ISN ...................................................................100V
TG, GATE...............................................................Note 2
CSP, CSN ................................................................100V
V
S
- CSP, V
S
- CSN ....................................... –0.3V to 4V
INTV
CC
(Note 3) .....................................8.6V, V
IN
+ 0.3V
PWM,
VMODE, FAULT
...............................................12V
FB1, FB2, SYNC (LT3796), TGEN (LT3796-1) ..............8V
CTRL .........................................................................15V
SENSE ......................................................................0.5V
ISMON, CSOUT ...........................................................5V
V
C
, V
REF
, SS ................................................................3V
RT ...............................................................................2V
Operating Junction Temperature Range (Note 4)
LT3796E/LT3796I .................................. –40 to 125°C
LT3796H ................................................ –40 to 150°C
Storage Temperature Range ......................–65 to 150°C
V
REF
10
SS 11
RT 12
TGEN/SYNC* 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
*SYNC FOR LT3796, TGEN FOR LT3796-1
orDer inForMaTion
LEAD FREE FINISH
LT3796EFE#PBF
LT3796IFE#PBF
LT3796HFE#PBF
LT3796EFE-1#PBF
LT3796IFE-1#PBF
LT3796HFE-1#PBF
TAPE AND REEL
LT3796EFE#TRPBF
LT3796IFE#TRPBF
LT3796HFE#TRPBF
LT3796EFE-1#TRPBF
LT3796IFE-1#TRPBF
LT3796HFE-1#TRPBF
PART MARKING*
LT3796FE
LT3796FE
LT3796FE
LT3796FE-1
LT3796FE-1
LT3796FE-1
PACKAGE DESCRIPTION
28-Lead Plastic TSSOP
28-Lead Plastic TSSOP
28-Lead Plastic TSSOP
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
–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/
3796fb
2
For more information
www.linear.com/3796
LT3796/LT3796-1
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
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 Over Current Protection Threshold
(V
(ISP-ISN)
)
CTRL 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
FB1, FB2 Regulation Voltage (V
FB
)
FB1 Amplifier g
m
FB2 Amplifier g
m
FB1, FB2 Pin Input Bias Current
FB1 Open LED Threshold
C/10 Comparator Threshold (V
(ISP-ISN)
)
FB1 Overvoltage Threshold
FB2 Overvoltage Threshold
V
C
Current Mode Gain (∆V
VC
/∆V
SENSE
)
FB = V
FB
VMODE
Falling, ISP = ISN = 48V
VMODE
Falling, FB1 = 1.25V, ISP = 48V
VMODE
Falling, FB1 = 1.25V, ISN = 0V
FAULT
Falling
TG Rising
PWM = 0V
ISP = ISN = 48V
ISP = ISN = 48V
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, CTRL = 2V, PWM = 5V, unless otherwise noted.
CONDITIONS
V
IN
Tied to INTV
CC
EN/UVLO = 0V, PWM = 0V
EN/UVLO = 1.15V, PWM = 0V
R
T
= 82.5k to GND, FB1 = 1.5V
–100µA ≤ I
REF
≤ 10µA
6V < V
IN
< 100V
–100µA < I
REF
< 0µA
l
l
MIN
TYP
MAX
6
1
12
UNITS
V
µA
µA
mA
V
m%/V
m%/µA
2.5
1.97
2.015
1.5
10
100
113
60
28
2.8
l
l
l
l
l
l
l
l
l
l
l
l
3
2.06
125
mV
µA
µA
µA
Current Out of Pin
SS = 0V
ISP – ISN = 1V, SS = 2V
ISP = 48V, CTRL ≥ 1.2V
ISP = 0V, CTRL ≥ 1.2V
CTRL = 1V, ISP = 48V
CTRL = 1V, ISP = 0V
CTRL = 0.6V, ISP = 48V
CTRL = 0.6V, ISP = 0V
CTRL = 0.2V, ISP = 48V
CTRL = 0.2V, ISP = 0V
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 = 1.2V
0
PWM = 5V (Active), ISP = 48V
PWM = 0V (Standby), ISP = 48V
V
(ISP-ISN)
= 250mV
–20
1.230
1.238
450
130
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
131
131
32
32
1.04
1.04
390
390
200
100
mV
mV
mV
mV
mV
mV
mV
mV
V
V
mV
mV
nA
V
µA
µA
µs
kΩ
700
0
400
2000
0.1
20
1.250
1.250
600
170
100
25
25
1.270
1.264
750
210
200
nA
V
V
µS
µS
nA
V
mV
mV
V
V
V/V
V
FB
– 70mV V
FB
– 60mV V
FB
– 50mV
V
FB
+ 35mV V
FB
+ 50mV V
FB
+ 60mV
V
FB
+ 35mV V
FB
+ 50mV V
FB
+ 60mV
4.2
3796fb
For more information
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3
LT3796/LT3796-1
elecTrical characTerisTics
PARAMETER
Current Sense Amplifier (CSA)
Power Supply Voltage Range (V
S
)
CSA Input Voltage Common Mode Range
(V
CSP
and V
CSN
)
CSOUT Maximum Output Current
Input Voltage Offset (V
(CSP-CSN)
)
CSP CSN Input Bias Current
,
CSP CSN Input Current Offset
,
V
S
Supply Current
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 6)
(Note 6)
l
l
l
l
l
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, CTRL = 2V, PWM = 5V, unless otherwise noted.
CONDITIONS
MIN
3
2.5
TYP
MAX
100
100
200
–3
0
100
0
80
1
7.4
20
85
10
3.8
4
150
85
340
900
105
400
1000
190
210
0.96
1.185
0.4
2.5
3
40
3.8
200
300
300
40
0.4
1.5
40
0.4
1.5
1
10
l
UNITS
V
V
µA
mV
nA
nA
µA
µs
V
SNS
= 100mV, V
S
= 48V (Note 5)
R
IN1
= R
IN2
= 1k (Note 5)
R
IN1
= R
IN2
= 1k (Note 5)
V
S
= 48V
l
3
Input Step Response ( to 50% of Output Step) ∆V
SENSE
= 100mV Step, R
IN1
= R
IN2
= 1k, R
OUT
= 5k
7.7
400
8
V
mV
mA
mA
µA
I
INTVCC
= –10mA, V
IN
= 6V
V
IN
= 100V, INTV
CC
= 6V
V
IN
= 12V, INTV
CC
= 6V
EN/UVLO = 0V, INTV
CC
= 7V
4.1
V
mV
125
480
1150
kHz
kHz
kHz
ns
ns
Minimum Off-Time
Minimum On-Time
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
VMODE
OUTPUT Low
FAULT
OUTPUT Low
SYNC Pin Resistance to GND
SYNC Input Low Threshold
SYNC Input High Threshold
TGEN Pin Resistance to GND
TGEN Input Low Threshold
TGEN Input High Threshold
1.04
1.250
V
µA
V
mV
V
µA
nA
mV
mV
kΩ
V
V
kΩ
V
V
3796fb
1.220
20
I
VIN
Drops Below 1µA
EN/UVLO = 1.15V
EN/UVLO = 1.30V
I
VMODE
= 0.5mA
I
FAULT
= 0.5mA
LT3796 Only
LT3796 Only
LT3796 Only
LT3796-1 Only
LT3796-1 Only
LT3796-1 Only
4
For more information
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LT3796/LT3796-1
elecTrical characTerisTics
PARAMETER
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
)
C
L
= 300pF
C
L
= 300pF
ISP = 48V
PWM = 0V, ISP = 48V
INTV
CC
–
0.05
50
100
7
0
8
0.3
C
L
= 3300pF 10% to 90%
,
C
L
= 3300pF 10% to 90%
,
20
18
0.05
ns
ns
V
V
ns
ns
V
V
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, CTRL = 2V, PWM = 5V, unless otherwise noted.
MIN
TYP
MAX
UNITS
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 LT3796E and LT3796E-1 are guaranteed to meet specified
performance from 0°C to 125°C. Specifications over the –40°C to 125°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls. The LT3796I and LT3796I-1
are guaranteed to meet performance specifications over the –40°C to
125°C operating temperature range. The LT3796H and LT3796H-1 are
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:
Measured in servo. See Figure 9 for details.
Note 6:
See Duty Cycle Considerations in the Applications Information
section.
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5
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