LT3799IMSE#TRPBF [Linear]
LT3799 - Offline Isolated Flyback LED Controller with Active PFC; Package: MSOP; Pins: 16; Temperature Range: -40°C to 85°C;
| 型号： | LT3799IMSE#TRPBF |
| 厂家： | 
Linear |
| 描述： | LT3799 - Offline Isolated Flyback LED Controller with Active PFC; Package: MSOP; Pins: 16; Temperature Range: -40°C to 85°C 驱动 功率因数校正 光电二极管 接口集成电路 |
| 文件： | 总20页 (文件大小：898K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT3799
Offline Isolated Flyback
LED Controller with Active PFC
FEATURES
DESCRIPTION
The LT®3799 is an isolated flyback controller with power
factor correction specifically designed for driving LEDs.
The controller operates using critical conduction mode
allowing the use of a small transformer. Using a novel
current sensing scheme, the controller is able to deliver a
well regulated current to the secondary side without using
an opto-coupler. A strong gate driver is included to drive
an external high voltage MOSFET. Utilizing an onboard
multiplier, the LT3799 typically achieves power factors
of 0.97. The FAULT pin provides notification of open and
short LED conditions.
n
Isolated PFC LED Driver with Minimum Number of
External Components
n
TRIAC Dimmable
n
V and V
Limited Only by External Components
IN
OUT
n
n
n
n
n
n
Active Power Factor Correction (Typical PFC > 0.97)
Low Harmonic Content
No Opto-Coupler Required
Accurate Regulated LED Current (±±5 Typical)
Open LED and Shorted LED Protection
Thermally Enhanced 16-Lead MSOP Package
APPLICATIONS
The LT3799 uses a micropower hysteretic start-up to
efficiently operate at offline input voltages, with a third
winding to provide power to the part. An internal LDO
provides a well regulated supply for the part’s internal
circuitry and gate driver.
n
Offline 4W to 100W+ LED Applications
n
High DC V LED Applications
IN
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. Patents pending.
TYPICAL APPLICATION
TRIAC Dimmable 20W LED Driver
LED Current vs Input Voltage
1.20
1.15
100k
100k
90V
TO 150V
AC
20Ω
0.22µF
200Ω
4:1:1
1.10
0.1µF
499k
499k
4.7pF
10µF
1.05
1.00
2k
1A
100k
V
DCM
FB
IN
0.95
V
IN_SENSE
0.90
4.99k
560µF
× 2
LT3799
6.34k
40.2k
0.85
0.80
V
REF
20W
20Ω
90
100
110
120
(V
130
140
150
LED
100k
32.4k
CTRL3
CTRL2
CTRL1
GATE
V
)
IN AC
POWER
3799 TA01b
SENSE
INTV
CC
0.05Ω
100k
NTC
4.7µF
16.2k
2.2nF
GND
–
+
FAULT
FAULT CT COMP COMP
3799 TA01a
0.1µF
0.1µF
3799fb
1
For more information www.linear.com/LT3799
LT3799
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
V , FAULT .................................................................32V
IN
1
2
3
4
5
6
7
8
V
IN_SENSE
CTRL1
CTRL2
CTRL3
16
15
14
13
12
11
10
9
GATE, INTV ...........................................................12V
SENSE
GATE
CC
–
CTRL1, CTRL2, CTRL3, V
, COMP ................4V
V
17
GND
INTV
CC
NC
REF
IN_SENSE
FAULT
+
FB, CT, V
COMP ,...................................................3V
CT
REF,
V
IN
+
COMP
DCM
FB
SENSE......................................................................0.4V
DCM.......................................................................±3mA
Maximum Junction Temperature .......................... 12±°C
Operating Temperature Range (Note 2)
–
COMP
MSE PACKAGE
16-LEAD PLASTIC MSOP
θ
JA
= ±0°C/W, θ = 10°C/W
JC
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
LT3799E ............................................ –40°C to 12±°C
LT3799I ............................................. –40°C to 12±°C
Storage Temperature Range .................. –6±°C to 1±0°C
ORDER INFORMATION
(http://www.linear.com/product/LT3799#orderinfo)
LEAD FREE FINISH
LT3799EMSE#PBF
LT3799IMSE#PBF
TAPE AND REEL
PART MARKING*
3799
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3799EMSE#TRPBF
LT3799IMSE#TRPBF
16-Lead Plastic MSOPE
16-Lead Plastic MSOPE
–40°C to 12±°C
–40°C to 12±°C
3799
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/
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 18V, INTVCC = 11V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
22.2
11.8
TYP
23
MAX
24.2
13.0
UNITS
V
IN
V
IN
V
IN
V
IN
V
IN
V
IN
Turn-On Voltage
V
V
Turn-Off Voltage
12.3
10.7
2±.0
Hysteresis
V
– V
V
TURNON
TURNOFF
Shunt Regulator Voltage
Shunt Regulator Current Limit
Quiescent Current
I = 1mA
V
1±
±±
mA
Before Turn-On
After Turn-On
6±
70
7±
µA
µA
INTV Quiescent Current
Before Turn-On
After Turn-On
12
1.±
16
1.2
20.0
2.6
µA
mA
CC
V
V
V
Threshold
Turn-Off
30
0
6±
90
mV
V
IN_SENSE
Linear Range
1.3
IN_SENSE
l
l
Voltage
0µA Load
200µA Load
1.97
1.9±
2
1.98
2.03
2.03
V
V
REF
+
–
, CTRL1 = 1V, CTRL2 = 2V, CTRL3 = 2V
Error Amplifier Voltage Gain
∆V
/∆V
100
±0
V/V
COMP
COMP
Error Amplifier Transconductance
∆I = ±µA
µmhos
3799fb
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For more information www.linear.com/LT3799
LT3799
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 18V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
600
±2±
106
UNITS
nA
FB Pin Bias Current
(Note 3), FB = 1V
CTRL/CTRL2/CTRL3 = 1V
100
CTRL1/CTRL2/CTRL3 Pin Bias Current
Maximum SENSE Current Limit Threshold
SENSE Input Bias Current
Current Loop Voltage Gain
CT Pin Charge Current
nA
96
100
1±
mV
µA
Current Out of Pin, SENSE = 0V
+
–
∆V
CTRL
/∆V
, 1000pF Cap from COMP to COMP
21
V/V
µA
SENSE
10
CT Pin Discharge Current
CT Pin Low Threshold
200
240
1.2±
100
1.2±
4±
nA
Falling Threshold
Rising Threshold
mV
V
CT Pin High Threshold
CT Pin Low Hysteresis
mV
V
FB Pin High Threshold
1.22
1.29
DCM Current Turn-On Threshold
Maximum Oscillator Frequency
Minimum Oscillator Frequency
Back-Up Oscillator Frequency
Linear Regulator
Current Out of Pin
µA
+
COMP = 1.2V, V
= 1V
300
2±
kHz
kHz
kHz
IN_SENSE
IN_SENSE
+
COMP = 0V, V
20
INTV Regulation Voltage
9.8
10
7±0
2±
10.4
V
mV
mA
mA
CC
Dropout (V – INTV
)
INTV = –10mA; Below V Turn-Off Voltage
11±0
IN
CC
CC
IN
Current Limit
Current Limit
Gate Driver
Below Undervoltage Threshold
Above Undervoltage Threshold
12
80
120
t GATE Driver Output Rise Time
C = 3300pF, 105 to 905
20
20
ns
ns
V
r
L
t GATE Driver Output Fall Time
f
C = 3300pF, 905 to 105
L
GATE Output Low (V
)
OL
0.0±
GATE Output High (V
)
OH
INTV
V
CC
– 0.0±
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.
to 12±°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3799I is guaranteed to meet performance specifications from –40°C to
12±°C operating junction temperature.
Note 2: The LT3799E is guaranteed to meet performance specifications
Note 3: Current flows out of the FB pin.
from 0°C to 12±°C junction temperature. Specifications over the –40°C
3799fb
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For more information www.linear.com/LT3799
LT3799
TYPICAL PERFORMANCE CHARACTERISTICS
VIN Start-Up Voltage
vs Temperature
Input Voltage Hysteresis
vs Temperature
VIN IQ vs Temperature
24.0
23.5
23.0
22.5
22.0
12.0
11.6
11.2
10.8
10.4
10.0
140
120
100
80
V
V
= 24V
= 12V
IN
IN
60
40
20
0
–50
0
25
TEMPERATURE (°C)
50
75 100 125
–50
0
25
TEMPERATURE (°C)
50
75 100
125
–25
–25
–50
0
25
50
75 100 125
–25
3799 G01
3799 G03
TEMPERATURE (°C)
VREF vs Temperature
VREF vs VIN
Current Limit vs Temperature
2.100
2.075
2.050
2.025
2.000
1.975
1.950
1.925
1.900
2.100
2.075
2.050
2.025
2.000
1.975
1.950
1.925
1.900
120
100
80
60
40
20
0
MAX I
LIM
NO LOAD
NO LOAD
200µA LOAD
200µA LOAD
MIN I
25
LIM
50
14
18 20 22 24 26 28 30 32
(V)
16
–50
0
25
50
75 100 125
–50
0
75 100 125
–25
–25
V
TEMPERATURE (°C)
TEMPERATURE (°C)
IN
3799 G05
3799 G05
3799 G06
Maximum Oscillator Frequency
vs Temperature
Minimum Oscillator Frequency
vs Temperature
375
350
325
300
275
250
225
70
60
50
40
30
20
10
–50
0
25
50
75 100 125
–50
0
25
50
75 100 125
–25
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
3799 G07
3799 G08
3799fb
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For more information www.linear.com/LT3799
LT3799
TYPICAL PERFORMANCE CHARACTERISTICS
CT Pin Charge Current
vs Temperature
CT Pin Discharge Current
vs Temperature
CT Pin Low Threshold
vs Temperature
200
190
180
170
160
150
12
10
8
0.4
0.3
0.2
0.1
0
6
4
2
0
–50
0
25
50
75 100 125
–25
–50
0
25
50
75 100 125
–50
0
25
50
75 100 125
–25
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3799 G10
3799 G09
3799 G11
CT Pin High Threshold
vs Temperature
INTVCC vs Temperature
INTVCC vs VIN
1.5
1.4
1.3
1.2
1.1
1.0
10.6
10.4
10.2
10.0
9.8
10.25
10.20
10.15
10.10
10.05
10.00
9.95
NO LOAD
PART ON
10mA LOAD
9.6
PART OFF
14 16 18 20 22 24 26 28 30 34
9.4
–50
0
25
50
75 100 125
–25
50
–50
0
25
75 100 125
10
12
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
V
(V)
IN
3799 G12
3799 G13
3799 G14
Maximum Shunt Current
vs Temperature
VIN Shunt Voltage vs Temperature
LED Current vs TRIAC Angle
26.00
25.75
25.50
25.25
25.00
24.75
24.50
30
25
20
15
10
5
1.2
1.0
0.8
0.6
0.4
0.2
0
PAGE 17 SCHEMATIC
220V APPLICATION
120V APPLICATION
I
= 10mA
SHUNT
0
–50
0
25
50
75 100 125
–25
120
TRIAC ANGLE (DEGREES)
180
–50
0
25
50
75 100 125
0
60
90
150
–25
30
TEMPERATURE (°C)
TEMPERATURE (°C)
3799 G15
3799 G16
3799 G17
3799fb
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For more information www.linear.com/LT3799
LT3799
TYPICAL PERFORMANCE CHARACTERISTICS
LED Current vs Input Voltage
LED Current vs Input Voltage
LED Current vs Input Voltage
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
PAGE 17 SCHEMATIC:
UNIVERSAL
PAGE 17 SCHEMATIC:
OPTIMIZED FOR 120V
PAGE 17 SCHEMATIC:
OPTIMIZED FOR 220V
90 110 130 150 170 190 210 230 250 270
90
100
110
120
130
140
150
170 180 190 200 210 220 230 240 250 260 270
(V
V
(V )
IN AC
V
(V
IN AC
)
V
)
IN AC
3799 G20
3799 G18
3799 G19
Power Factor vs Input Voltage
Power Factor vs Input Voltage
Power Factor vs Input Voltage
1.00
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0.91
1.00
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0.91
1.00
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0.91
PAGE 17 SCHEMATIC:
OPTIMIZED FOR 220V
PAGE 17 SCHEMATIC:
UNIVERSAL
PAGE 17 SCHEMATIC:
OPTIMIZED FOR 120V
0.90
0.90
0.90
90
100
110
120
(V
130
140
150
170 180 190 200 210 220 230 240 250 260 270
(V
90 110 130 150 170 190 210 230 250 270
V
)
V
)
V
(V )
IN AC
IN AC
IN AC
3799 G21
3799 G22
3799 G23
Efficiency vs Input Voltage
Efficiency vs Input Voltage
Efficiency vs Input Voltage
100
95
90
85
80
75
70
65
60
100
95
90
85
80
75
70
65
60
100
95
90
85
80
75
70
65
60
PAGE 17 SCHEMATIC:
OPTIMIZED FOR 120V
PAGE 17 SCHEMATIC:
UNIVERSAL
PAGE 17 SCHEMATIC:
OPTIMIZED FOR 220V
170 180 190 200 210 220 230 240 250 260 270
(V
90 110 130 150 170 190 210 230 250 270
90
100
110
120
(V
130
140
150
V
)
V
)
V (V )
IN AC
IN AC
IN AC
3799 G24
3799 G25
3799 G26
3799fb
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For more information www.linear.com/LT3799
LT3799
PIN FUNCTIONS
CTRL1,CTRL2,CTRL3(Pin1,Pin2,Pin3):CurrentOutput
Adjustment Pins. These pins control the output current.
The lowest value of the three CTRL inputs is compared to
the negative input of the operational amplifier. Due to the
unique nature of the LT3799 control loop, the maximum
DCM(Pin10):DiscontinuousConductionModeDetection
Pin. Connect a capacitor and resistor in series with this
pin to the third winding.
V (Pin 11): Input Voltage. This pin supplies current to
IN
the internal start-up circuitry and to the INTV LDO. This
CC
currentdoesnotdirectlycorrespondtotheV
voltages.
CTRL
pin must be locally bypassed with a capacitor. A 2±V shunt
V
(Pin 4): Voltage Reference Output Pin, Typically 2V.
regulator is internally connected to this pin.
REF
This pin drives a resistor divider for the CTRL pin, either
foranalogdimmingorfortemperaturelimit/compensation
of LED load. Can supply up to 200µA.
INTV (Pin 13): Regulated Supply for Internal Loads
CC
and GATE Driver. Supplied from V and regulates to 10V
IN
(typical). INTV must be bypassed with a 4.7µF capacitor
CC
FAULT (Pin 5): Fault Pin. An open-collector pull-down on
FAULT asserts if FB is greater than 1.2±V with the CT pin
higher than 1.2±V.
placed close to the pin.
GATE (Pin 14): N-Channel MOSFET Gate Driver Output.
Switches between INTV and GND. This pin is pulled to
CC
CT (Pin 6): Timer Fault Pin. A capacitor is connected
between this pin and ground to provide an internal timer
for fault operations. During start-up, this pin is pulled to
groundandthenchargedwitha10µAcurrent.Faultsrelated
to the FB pin will be ignored until the CT pin reaches 1.2±V.
If a fault is detected, the controller will stop switching and
begintodischargetheCTcapacitorwitha200nApull-down
current. When the pin reaches 240mV, the controller will
start to switch again.
GND during shutdown state.
SENSE (Pin 15): The Current Sense Input for the Control
Loop. Kelvin connect this pin to the positive terminal of
the switch current sense resistor, R
, and the source
SENSE
of the N-channel MOSFET. The negative terminal of the
current sense resistor should be connected to the GND
plane close to the IC.
V
(Pin16):LineVoltageSensePin.Thepinisused
IN_SENSE
for sensing the AC line voltage to perform power factor
correction. Connect the output of a resistor divider from
the line voltage to this pin. The voltage on this pin should
be between 1.2±V to 1.±V at the maximum input voltage.
+
–
COMP , COMP (Pin 7, Pin 8): Compensation Pins for
InternalErrorAmplifier.Connectacapacitorbetweenthese
two pins to compensate the internal feedback loop.
FB (Pin 9): Voltage Loop Feedback Pin. FB is used to
detect open LED conditions by sampling the third winding
voltage. An open LED condition is reported if the CT pin
and the FB pin are higher than 1.2±V.
GND (Exposed Pad Pin 17): Ground. The exposed pad
of the package provides both electrical contact to ground
and good thermal contact to the printed circuit board.
The exposed pad must be soldered to the circuit board
for proper operation.
3799fb
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For more information www.linear.com/LT3799
LT3799
BLOCK DIAGRAM
V
IN
D2
D1
R3
T1
+
–
V
OUT
OUT
•
R4
R5
R1
R2
C3
C2
C1
L1A
L1B
L1C
C7
V
R10
N:1
9
10
16
11
FB
DCM
V
V
IN
IN_SENSE
S&H
A3
CT
FAULT
DETECTION
6
5
1.22V
+
–
A8
C4
INTV
CC
13
FAULT
R7
C5
+
–
ONE
SHOT
A2
CURRENT
COMPARATOR
+
–
R8
600mV
–
A1
+
+
–
A7
COMP
S
S
R
DRIVER
GATE
SENSE
GND
7
14
15
17
M1
R6
Q
C6
1M
A5
MASTER
LATCH
SW1
COMP
A4
8
1
2
3
4
CTRL1
CTRL2
CTRL3
–
+
+
+
A6
LOW OUTPUT
MULTIPLIER
CURRENT
OSCILLATOR
V
REF
3799 BD
OPERATION
The LT3799 is a current mode switching controller IC
designed specifically for generating an average current
outputinanisolatedflybacktopology.Thespecialproblem
normally encountered in such circuits is that information
relating to the output voltage and current on the isolated
secondarysideofthetransformermustbecommunicated
totheprimarysideinordertomaintainregulation. Histori-
cally, this has been done with an opto-isolator. The LT3799
uses a novel method of using the external MOSFETs peak
current information from the sense resistor to calculate
the output current of a flyback converter without the need
of an opto-coupler. In addition, it also detects open LED
conditions by examining the third winding voltage when
the main power switch is off.
Power factor has become an important specification for
lighting. A power factor of one is achieved if the current
drawn is proportional to the input voltage. The LT3799
modulates the peak current limit with a scaled version of
the input voltage. This technique provides power factors
of 0.97 or greater.
The Block Diagram shows an overall view of the system.
The external components are in a flyback topology con-
figuration. The third winding senses the output voltage
and also supplies power to the part in steady-state opera-
tion. The V pin supplies power to an internal LDO that
IN
generates10VattheINTV pin.Thenovelcontrolcircuitry
CC
consists of an error amplifier, a multiplier, a transmission
3799fb
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For more information www.linear.com/LT3799
LT3799
OPERATION
gate, a current comparator, a low output current oscillator
and a master latch, which will be explained in the follow-
ing sections. The part also features a sample-and-hold
to detect open LED conditions, along with a FAULT pin. A
comparator is used to detect discontinuous conduction
mode (DCM) with a cap connected to the third winding.
The part features a 1.9A gate driver.
for the ringing waveform to reach its minimum value and
then the switch turns back on. This switching behavior is
similartozerovoltswitchingandminimizestheamountof
energy lost when the switch is turned back on, improving
efficiency as much as ±5. Since this part operates on the
edge of continuous conduction mode and discontinuous
conduction mode, this operating mode is called critical
conduction mode (or boundary conduction mode).
The LT3799 employs a micropower hysteretic start-up
feature to allow the part to work at any combination of
inputandoutputvoltages.IntheBlockDiagram,R3isused
to stand off the high voltage supply voltage. The internal
Primary-Side Current Control Loop
The CTRL1/CTRL2/CTRL3 pins control the output current
of the flyback controller. To simplify the loop, assume
LDO starts to supply current to the INTV when V is
CC
IN
the V
pin is held at a constant voltage above
IN_SENSE
above 23V. The V and INTV capacitors are charged by
IN
CC
1V, eliminating the multiplier from the control loop. The
the current from R3. When V exceeds 23V and INTV is
IN
CC
error amplifier, A±, is configured as an integrator with
the external capacitor, C6. The COMP node voltage is
in regulation at 10V, the part will began to charge the CT
+
pin with 10µA. Once the CT pin reaches 340mV, switching
converted to a current into the multiplier with the V/I
converter, A6. Since A7’s output is constant, the output
of the multiplier is proportional to A6 and can be ignored.
The output of the multiplier controls the peak current with
its connection to the current comparator, A1. The output
of the multiplier is also connected to the transmission
gate, SW1. The transmission gate, SW1, turns on when
the secondary current flows to the output capacitor. This
is called the flyback period (when the output diode D1 is
on). The current through the 1M resistor gets integrated
byA±. ThelowestCTRLinputisequaltothenegativeinput
of A± in steady state.
begins. The V pin has 10.7V of hysteresis to allow for
IN
plenty of flexibility with the input and output capacitor
values. The third winding provides power to V when its
IN
voltage is higher than the V voltage. A voltage shunt is
IN
provided for fault protection and can sink up to 1±mA of
current when V is over 2±V.
IN
During a typical cycle, the gate driver turns the external
MOSFET on and a current flows through the primary
winding. This current increases at a rate proportional
to the input voltage and inversely proportional to the
magnetizing inductance of the transformer. The control
loop determines the maximum current and the current
comparator turns the switch off when the current level
is reached. When the switch turns off, the energy in the
core of the transformer flows out the secondary winding
through the output diode, D1. This current decreases at a
rate proportional to the output voltage. When the current
decreases to zero, the output diode turns off and voltage
across the secondary winding starts to oscillate from the
parasitic capacitance and the magnetizing inductance of
the transformer. Since all windings have the same voltage
across them, the third winding rings too. The capacitor
connected to the DCM pin, C1, trips the comparator, A2,
which serves as a dv/dt detector, when the ringing occurs.
This timing information is used to calculate the output
current (description to follow). The dv/dt detector waits
A current output regulator normally uses a sense resistor
in series with the output current and uses a feedback loop
to control the peak current of the switching converter. In
this isolated case the output current information is not
available, so instead the LT3799 calculates it using the
information available on the primary side of the trans-
former.Theoutputcurrentmaybecalculatedbytakingthe
average of the output diode current. As shown in Figure
1, the diode current is a triangle waveform with a base of
the flyback time and a height of the peak secondary wind-
ing current. In a flyback topology, the secondary winding
current is N times the primary winding current, where
N is the primary to secondary winding ratio. Instead of
taking the area of the triangle, think of it as a pulse width
modulation (PWM) waveform. During the flyback time,
the average current is half the peak secondary winding
3799fb
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For more information www.linear.com/LT3799
LT3799
OPERATION
voltage is 120Hz, so the control loop unity gain frequency
needs to be set less than approximately 120Hz. Without a
large amount of energy storage on the secondary side, the
output current is affected by the supply voltage changes,
but the DC component of the output current is accurate.
I
PK(sec)
SECONDARY
DIODE CURRENT
TRIAC Dimming Features
SWITCH
WAVEFORM
The LT3799 incorporates some special features that aid in
thedesignofanofflineLEDcurrentsourcewhenusedwith
a TRIAC dimmer. TRIAC dimmers are not ideal switches
when turned off and allow milliamps of current to flow
through them. This is an issue if used with a low quiescent
partsuchastheLT3799.Insteadofturningthemainpower
MOSFET off when the TRIAC is off, this power device is
kept on and sinks the current to properly load the TRIAC.
T
FLYBACK
3799 F01
T
PERIOD
Figure 1. Secondary Diode Current and Switch Waveforms
current and zero during the rest of the cycle. The equation
for expressing the output current is:
When the TRIAC turns on, the V
pin detects this
IN_SENSE
I
= 0.± • I • N • D´
PK
OUT
andenablestheloop, butthecurrentcomparatorisalways
enabled and turns the switch off if it is tripped.
whereD´isequaltothepercentageofthecyclerepresented
by the flyback time.
Start-Up
The LT3799 has access to both the primary winding cur-
rent, the input to the current comparator, and when the
flyback time starts and ends. Now the output current can
be calculated by averaging a PWM waveform with the
height of the current limit and the duty cycle of the flyback
time over the entire cycle. In the feedback loop previously
described, the input to the integrator is such a waveform.
The integrator adjusts the peak current until the calculated
output current equals the control voltage. If the calculated
outputcurrentislowcomparedtothecontrolpin,theerror
The LT3799 uses a hysteretic start-up to operate from
high offline voltages. A resistor connected to the supply
voltage protects the part from high voltages. This resis-
tor is connected to the V pin on the part and also to a
IN
capacitor.Whentheresistorchargesthepartupto23Vand
INTV isinregulationat10V, thepartbeginstochargethe
CC
CT pin to 340mV and then starts to switch. The resistor
does not provide power for the part in steady state, but
relies on the capacitor to start-up the part, then the third
+
winding begins to provide power to the V pin along with
IN
amplifier increases the voltage on the COMP node, thus
increasing the current comparator input.
the resistor. An internal voltage clamp is attached to the
V pin to prevent the resistor current from allowing V
IN
IN
When the V
voltage is connected to a resistor
IN_SENSE
to go above the absolute maximum voltage of the pin.
The internal clamp is set at 2±V and is capable of 28mA
(typical) of current at room temperature. But, ideally, the
divider of the supply voltage, the current limit is propor-
+
tional to the supply voltage if COMP is held constant.
The output of the error amplifier is multiplied with the
resistor connected between the input supply and the V
IN
V
pin voltage. If the LT3799 is configured with a
IN_SENSE
pin should be chosen so that less than 10mA is being
fast control loop, slower changes from the V
pin
IN_SENSE
shunted by this internal clamp.
willnotinterferewiththecurrentlimitortheoutputcurrent.
+
TheCOMP pinwilladjusttothechangesoftheV
.
CT Pin and Faults
IN_SENSE
The only way for the multiplier to function properly is to
set the control loop to be an order of magnitude slower
The CT pin is a timing pin for the fault circuitry. When the
input voltages are at the correct levels, the CT pin sources
10µA of current. When the CT pin reaches 340mV, the part
thanthefundamentalfrequencyoftheV
signal. In
IN_SENSE
the offline case, the fundamental frequency of the supply
3799fb
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For more information www.linear.com/LT3799
LT3799
OPERATION
begins to switch. The output voltage information from the
FB pin is sampled but ignored until the CT pin reaches
1.2±V. When this occurs, if the FB pin is above 1.2±V, the
fault flag pulls low. The FAULT pin is meant to be used
where
VOUT •N
VOUT •N+ V
D =
IN
with a large pull-up resistor to the INTV pin or another
CC
The maximum control voltage to achieve this maximum
output current is (1-D) • 47.±5.
supply. The CT pin begins to sink 200nA of current. When
the CT pin goes below 240mV, the part will re-enable itself,
begin to switch, and start to source 10µA of current to the
CT pin but not remove the fault condition. When the CT
pin reaches 1.2±V and FB is below 1.2±V, the FAULT pin
will no longer pull low and switching will continue. If not
below 1.2±V, the process repeats itself.
For control voltages below the maximum, the output cur-
rent is equal to the following equation:
N
IOUT = CTRL •
42 •RSENSE
The V
pin supplies a 2V reference voltage to be used
REF
Programming Output Current
with the control pins. To set an output current, a resistor
divider is used from the 2V reference to one of the control
pins. The following equation sets the output current with
a resistor divider:
The maximum output current depends on the supply
voltage and the output voltage in a flyback topology.
With the V
pin connected to 1V and a DC supply
IN_SENSE
voltage, the maximum output current is determined at
the minimum supply voltage, and the maximum output
voltage using the following equation:
ꢀ
ꢂ
ꢁ
ꢃ
2N
R1=R2
− 1
ꢅ
42 • IOUT • RSENSE
ꢄ
N
where R1 is the resistor connected to the V pin and the
CTRL pin and R2 is the resistor connected to the CTRL
pin and ground.
REF
I
OUT(MAX) = 2 •(1−D)•
42 •RSENSE
where
When used with an AC input voltage, the LT3799 senses
VOUT •N
when the V
goes below 6±mV and above 6±mV
IN_SENSE
D =
VOUT •N+ V
for detecting when the TRIAC is off. During this low input
voltagetime,theoutputcurrentregulationloopisoffbutthe
partstillswitches.Thishelpswithoutputcurrentregulation
with a TRIAC but introduces a line regulation error. When
IN
The maximum control voltage to achieve this maximum
output current is 2V • (1-D).
V
is low, very little power is being delivered to the
It is suggested to operate at 9±5 of these values to give
margin for the part’s tolerances.
IN_SENSE
output and since the output current regulation loop is off,
this time period needs to be accounted for in setting the
output current. This time period slightly varies with line
voltage. Figure 2 shows the correction factor in selecting
the resistor divider resistors. When used with AC, the fol-
lowingequationshouldbeusedwiththecorrectionfactor:
When designing for power factor correction, the output
currentwaveformisgoingtohaveahalfsinewavesquared
shape and will no longer be able to provide the above
currents. By taking the integral of a sine wave squared
over half a cycle, the average output current is found to
be half the value of the peak output current. In this case,
the recommended maximum average output current is
as follows:
N
I
OUT = CTRL •
42 •RSENSE • CF
ꢀ
ꢃ
2N
R1=R2
− 1
ꢅ
ꢂ
N
42 • IOUT • RSENSE •CF
IOUT(MAX) = 2•(1−D)•
• 47.5%
ꢁ
ꢄ
42 •RSENSE
3799fb
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For more information www.linear.com/LT3799
LT3799
OPERATION
1.16
1.14
1.12
1.10
1.08
1.06
1.04
primary winding of the transformer. The minimum volt-
age of the switch node during this discontinuous ring is
V
– V
• N. The LT3799 turns the switch back on at
IN
OUT
this time, during the discontinuous switch waveform, by
sensing when the slope of the switch waveform goes from
negativetopositiveusingthedv/dtdetector.Thisswitching
technique may increase efficiency by ±5.
Sense Resistor Selection
The resistor, R
, between the source of the external
1.02
0
SENSE
0.5
PEAK V
1
1.5
N-channelMOSFETandGNDshouldbeselectedtoprovide
anadequateswitchcurrenttodrivetheapplicationwithout
exceeding the current limit threshold .
IN_SENSE
3799 F02
Figure 2. Output Current Correction Factor
For applications without power factor correction, select a
resistor according to:
where CF is the output current correction factor on the
Y-axis in Figure 2.
2(1−D)N
RSENSE
=
• 95%
Critical Conduction Mode Operation
IOUT • 42
Criticalconductionmodeisavariablefrequencyswitching
scheme that always returns the secondary current to zero
with every cycle. The LT3799 relies on boundary mode
and discontinuous mode to calculate the critical current
because the sensing scheme assumes the secondary
current returns to zero with every cycle. The DCM pin
uses a fast current input comparator in combination with
a small capacitor to detect dv/dt on the third winding. To
eliminate false tripping due to leakage inductance ringing,
a blanking time of between 600ns and 2.2±µs is applied
after the switch turns off, depending on the current limit.
The detector looks for 40µA of current through the DCM
pin due to falling voltage on the third winding when the
secondary diode turns off. This detection is important
since the output current is calculated using this com-
parator’s output. This is not the optimal time to turn the
where
VOUT •N
VOUT •N+ V
D =
IN
For applications with power factor correction, select a
resistor according to:
2(1−D)N
IOUT • 42
RSENSE
=
• 47.5%
where
VOUT •N
VOUT •N+ V
D =
IN
Minimum Current Limit
switch on because the switch voltage is still close to V
IN
The LT3799 features a minimum current limit of approxi-
mately75ofthepeakcurrentlimit.Thisisnecessarywhen
operating in critical conduction mode since low current
limits would increase the operating frequency to a very
highfrequency.Theoutputvoltagesensingcircuitryneeds
a minimum amount of flyback waveform time to sense the
output voltage on the third winding. The time needed is
3±0ns.Theminimumcurrentlimitallowstheuseofsmaller
+ V
• N and would waste all the energy stored in the
OUT
parasitic capacitance on the switch node. Discontinuous
ringing begins when the secondary current reaches zero
and the energy in the parasitic capacitance on the switch
node transfers to the input capacitor. This is a second-
order network composed of the parasitic capacitance on
the switch node and the magnetizing inductance of the
3799fb
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For more information www.linear.com/LT3799
LT3799
OPERATION
transformers since the magnetizing primary inductance
does not need to be as high to allow proper time to sample
the output voltage information.
be minimized by using two application circuits for the
wide input range: one optimized for 120V and another
AC
optimized for 220V . The first application pictured in
AC
the Typical Applications section shows three options:
Errors Affecting Current Output Regulation
universal input, 120V , and 220V . The circuit varies by
AC
AC
threeresistors.IntheTypicalPerformanceCharacteristics
Thereareafewfactorsaffectingtheregulationofcurrentin
amanufacturingenvironmentalongwithsomesystematic
issues. The main manufacturing issues are the winding
turns ratio and the LT3799 control loop accuracy. The
winding turns ratio is well controlled by the transformer
manufacturer’swindingequipment,butmosttransformers
do not require a tight tolerance on the winding ratio. We
have worked with transformer manufacturers to specify
±15errorfortheturnsratio.JustlikeanyotherLEDdriver,
the part is tested and trimmed to eliminate offsets in the
control loop and an error of ±35 is specified at 805 of
the maximum output current. The error grows larger as
the LED current is decreased from the maximum output
current. At half the maximum output current, the error
doubles to ±65.
section, the LED Current vs V graphs show the output
IN
current line regulation for all three circuits.
Selecting Winding Turns Ratio
Boundarymodeoperationgivesalotoffreedominselecting
the turns ratio of the transformer. We suggest to keep the
duty cycle low, lower N , at the maximum input voltage
PS
since theduty cycle willincrease when the AC waveform is
decreases to zero volts. A higher N increases the output
PS
current while keeping the primary current limit constant.
Although this seems to be a good idea, it comes at the
expense of a higher RMS current for the secondary-side
diodewhichmightnotbedesirablebecauseoftheprimary
sideMOSFET’ssuperiorperformanceasaswitch.Ahigher
NPSdoesreducethevoltagestressonthesecondary-side
diode while increasing the voltage stress on the primary-
side MOSFET. If switching frequency at full output load is
kept constant, the amount of energy delivered per cycle by
Thereareanumberofsystematicoffsetsthatmaybeelimi-
natedbyadjustingthecontrolvoltagefromtheidealvoltage.
It is difficult to measure the flyback time with complete
accuracy. If this time is not accurate, the control voltage
needs to be adjusted from the ideal value to eliminate the
offset but this error still causes line regulation errors. If
the supply voltage is lowered, the time error becomes a
smaller portion of the switching cycle period so the offset
becomes smaller and vice versa. This error may be com-
pensated for at the primary supply voltage, but this does
notsolvetheproblemcompletelyforothersupplyvoltages.
Another systematic error is that the current comparator
cannot instantaneously turn off the main power device.
This delay time leads to primary current overshoot. This
overshoot is less of a problem when the output current is
close to its maximum, since the overshoot is only related
to the slope of the primary current and not the current
level. The overshoot is proportional to the supply voltage,
so again this affects the line regulation.
the transformer also stays constant regardless of the N .
PS
Therefore, the size of the transformer remains the same at
practical N ’s. Adjusting the turns ratio is a good way to
PS
find an optimal MOSFET and diode for a given application.
Switch Voltage Clamp Requirement
Leakage inductance of an offline transformer is high due
to the extra isolation requirement. The leakage inductance
energy is not coupled to the secondary and goes into
the drain node of the MOSFET. This is problematic since
400V and higher rated MOSFETs cannot always handle
this energy by avalanching. Therefore the MOSFET needs
protection. A transient voltage suppressor (TVS) and
diode are recommended for all offline application and
connected, as shown in Figure 3. The TVS device needs
a reverse breakdown voltage greater than (V
+ V )*N
OUT
f
where V
is the output voltage of the flyback converter,
Universal Input
OUT
V is the secondary diode forward voltage, and N is the
f
The LT3799 operates over the universal input range of
turns ratio.
90V to 26±V . Output current regulation error may
AC
AC
3799fb
13
For more information www.linear.com/LT3799
LT3799
OPERATION
V
SUPPLY
the LT3799. Table 1 shows the details of several of these
transformers.
Loop Compensation
The current output feedback loop is an integrator con-
figuration with the compensation capacitor between the
negative input and output of the operational amplifier.
This is a one-pole system therefore a zero is not needed
in the compensation. For offline applications with PFC,
the crossover should be set an order of magnitude lower
than the line frequency of 120Hz or 100Hz. In a typical
application, the compensation capacitor is 0.1µF.
GATE
3799 F03
Figure 3. Clamp
Transformer Design Considerations
Transformer specification and design is a critical part of
successfully applying the LT3799. In addition to the usual
list of caveats dealing with high frequency isolated power
supply transformer design, the following information
should be carefully considered. Since the current on the
secondarysideofthetransformerisinferredbythecurrent
sampled on the primary, the transformer turns ratio must
betightlycontrolledtoensure a consistentoutputcurrent.
In non-PFC applications, the crossover frequency may be
increased to improve transient performance. The desired
crossoverfrequencyneedstobesetanorderofmagnitude
below the switching frequency for optimal performance.
MOSFET and Diode Selection
With a strong 1.9A gate driver, the LT3799 can effectively
drive most high voltage MOSFETs. A low Q MOSFET is
g
A tolerance of ±±5 in turns ratio from transformer to
transformercouldresultinavariationofmorethan±±5in
outputregulation. Fortunately, mostmagneticcomponent
manufacturers are capable of guaranteeing a turns ratio
tolerance of 15 or better. Linear Technology has worked
with several leading magnetic component manufacturers
to produce predesigned flyback transformers for use with
recommendedtomaximizeefficiency.Inmostapplications,
the R
should be chosen to limit the temperature rise
DS(ON)
of the MOSFET. The drain of the MOSFET is stressed to
• N + V during the time the MOSFET is off and
V
OUT
PS
IN
the secondary diode is conducting current. But in most
applications,theleakageinductancevoltagespikeexceeds
this voltage. The voltage of this stress is determined
Table 1. Predesigned Transformers—Typical Specifications, Unless Otherwise Noted
TARGET
TRANSFORMER SIZE
L
N
P
R
R
SEC
APPLICATION
PRI
PSA
S
PRI
PART NUMBER (L × W × H)
(µH)
(N :N :N )
(mΩ)
(mΩ)
126
16±
2±
MANUFACTURER
Coilcraft
(V /I
OUT OUT
)
A
JA4429
21.1mm × 21.1mm × 17.3mm
400
1:0.24:0.24
6.67:1:1.67
20:1.0:±.0
6:1.0:1.0
4:1:0.71
2±2
22V/1A
10V/0.4A
3.8V/1.1A
18V/±A
7±08110210
7±0813002
7±0811330
7±0813144
7±0813134
7±0811291
7±0813390
1±.7±mm × 1±mm × 18.±mm
1±.7±mm × 1±mm × 18.±mm
43.2mm × 39.6mm × 30.±mm
16.±mm × 18mm × 18mm
16.±mm × 18mm × 18mm
31mm × 31mm × 2±mm
2000
2000
300
±100
6100
1±0
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
2±
600
2400
18±0
±±0
420
10±
1230
688
28V/0.±A
14V/1A
600
8:1:1.28
400
1:1:0.24
8±V/0.4A
90V/1A
43.18mm × 39.6mm ×
30.48mm
100
1:1:0.22
1±0
7±0811290
31mm × 31mm × 2±mm
460
±00
1:1:0.17
72:16:10
600
±60
80
Würth Elektronik
Premo
12±V/0.32A
30V/0.±A
X-11181-002
23.±mm × 21.4mm × 9.±mm
1000
3799fb
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For more information www.linear.com/LT3799
LT3799
OPERATION
by the switch voltage clamp. Always check the switch
waveform with an oscilloscope to make sure the leakage
inductance voltage spike is below the breakdown voltage
of the MOSFET. A transient voltage suppressor and diode
are slower than the leakage inductance voltage spike,
therefore causing a higher voltage than calculated.
switch proportional to the line voltage by using an internal
multiplier. A power factor of >0.97 is easily attainable for
mostapplicationsbyfollowingthedesignequationsinthis
datasheet. With proper design, LT3799 applications meet
IEC 6100-3-2 Class C harmonic standards.
Protection from Open LED and Shorted LED Faults
The secondary diode stress may be as much as
TheLT3799detectsoutputovervoltageconditionsbylook-
ing at the voltage on the third winding. The third winding
voltageisproportionaltotheoutputvoltagewhenthemain
power switch is off and the secondary diode is conducting
current. Sensing the output voltage requires delivering
power to the output. Using the CT pin, the part turns off
switching when a overvoltage condition occurs and re-
checks to see if the overvoltage condition has cleared, as
described in “CT Pin and Faults” in the Operation section.
This greatly reduces the output current delivered to the
output but a Zener is required to dissipate 25 of the set
output current during an open LED condition. The Zener
diode’s voltage needs to be 105 higher than the output
voltage set by the resistor divider connected to the FB pin.
Multiple Zener diodes in series may be needed for higher
outputpowerapplicationstokeeptheZener’stemperature
within the specification.
V
+ 2 • V /N due to the anode of the diode ringing
OUT
IN PS
with the secondary leakage inductance. An RC snubber
in parallel with the diode eliminates this ringing, so that
the reverse voltage stress is limited to V
With a high N and output current greater than 3A, the
+ V /N .
OUT
IN PS
PS
I
through the diode can become very high and a low
RMS
forward drop Schottky is recommended.
Discontinuous Mode Detection
The discontinuous mode detector uses AC-coupling to
detect the ringing on the third winding. A 10pF capacitor
with a ±00Ω resistor in series is recommended in most
designs. Depending on the amount of leakage inductance
ringing, an additional current may be needed to prevent
falsetrippingfromtheleakageinductanceringing.Aresis-
tor from INTV to the DCM pin adds this current. Up to
CC
an additional 100µA of current may be needed in some
cases. The DCM pin is roughly 0.7V, therefore the resistor
value is selected using the following equation:
During a shorted LED condition, the LT3799 operates at
the minimum operating frequency. In normal operation,
the third winding provides power to the IC, but the third
winding voltage is zero during a shorted LED condition.
10V −0.7V
R =
I
This causes the part’s V UVLO to shutdown switching.
IN
The part starts switching again when V has reached its
IN
where I is equal to the additional current into the DCM pin.
turn-on voltage.
Power Factor Correction/Harmonic Content
The LT3799 attains high power factor and low harmonic
content by making the peak current of the main power
3799fb
15
For more information www.linear.com/LT3799
LT3799
TYPICAL APPLICATIONS
Universal TRIAC Dimmable 20W LED Driver
L2
800µH
L1
33mH
BR1
R6
C3
C1
0.068µF
R7
D2
C5
90V
20Ω
0.22µF
100k
4:1:1
TO 265V
R3
R8
100k
AC
C4
4.7pF
499k
C2
0.1µF
R1
200Ω
R4
499k
R13
2k
10µF
D3
R4
100k
1A
D4
V
DCM
IN
V
FB
Z1
IN_SENSE
R15
R5
4.02k
Z2
C10
560µF
× 2
LT3799
4.99k
3.48k
D1
R16
20Ω
V
REF
20W
R18
100k
R16
32.4k
R9
40.2k
LED
CTRL3
CTRL2
CTRL1
GATE
M1
POWER
SENSE
R
S
INTV
CC
100k
NTC
C9
4.7µF
0.05Ω
C8
2.2nF
R10
15.4k
GND
+
–
FAULT
CT COMP
COMP
FAULT
3799 TA02
C7, 0.1µF
BR1: DIODES, INC. HD06
D1:
CENTRAL SEMICONDUCTOR CMR1U-06M
D2,D3: DIODES INC. BAV20W
DR: CENTRAL SEMICONDUCTOR CMR1U-02M
Z1:
Z2:
T1:
FAIRCHILD SMBJ170A
CENTRAL SEMICONDUCTOR CMZ5937B
COILCRAFT JA4429-AL
M1: FAIRCHILD FDPF15N65
Component Values for Input Voltage Ranges
R5 (Ω)
R10 (Ω)
16.2k
R (Ω)
R1 (Ω)
200
C2 (µF)
0.1
C3 (µF)
0.22
S
Optimized for 110V
Optimized for 220V
Universal
6.34k
3.48k
3.48k
0.0±
0.07±
0.0±
24.9k
1.00k
200
0.033
0.1
0.1
1±.4k
0.22
3799fb
16
For more information www.linear.com/LT3799
LT3799
TYPICAL APPLICATIONS
Universal Input TRIAC Dimmable 4W LED Driver
L1
3.3mH
C1
33nF
R20, 10k
L1
3.3mH
BR1
R21, 10k
R6
C3
R7
90V
TO 265V
AC
D2
C5
20Ω
68nF
100k
20:5:1
R3
L2, 3.3mH
R8
100k
C4
4.7pF
499k
C2
22nF
R1
750Ω
R4
499k
R13
10k
10µF
D3
R4
100k
1A
D4
V
DCM
IN
V
FB
Z1
IN_SENSE
R15
4.99k
R5
3.48k
LT3799
C10
1500µF
D1
4W
LED
POWER
R16
20Ω
V
REF
R18
100k
M1
CTRL3
CTRL2
CTRL1
GATE
R9
40.2k
Z2
SENSE
R
S
INTV
CC
C9
4.7µF
0.3Ω
C8
2.2nF
R10
32.4k
GND
+
–
FAULT
CT COMP
COMP
FAULT
3799 TA03
C7, 0.1µF
C6
0.1µF
BR1: DIODES, INC. HD06
D1: CENTRAL SEMICONDUCTOR CMR1U-06M
D2,D3: CENTRAL SEMICONDUCTOR CMMSHI-100
D4:
Z1:
Z2:
T1:
CENTRAL SEMICONDUCTOR CMSH2-40L
FAIRCHILD SMBJ170A
CENTRAL SEMICONDUCTOR CMZ59198
WÜRTH ELEKTRONIK WE-750813002
M1: FAIRCHILD FQU5N60
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For more information www.linear.com/LT3799
LT3799
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MSE Package
16-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1667 Rev D)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 ± 0.102
(.112 ± .004)
2.845 ± 0.102
(.112 ± .004)
0.889 ± 0.127
(.035 ± .005)
1
8
0.35
REF
5.23
(.206)
MIN
1.651 ± 0.102
(.065 ± .004)
1.651 ± 0.102
(.065 ± .004)
3.20 – 3.45
(.126 – .136)
0.12 REF
DETAIL “B”
CORNER TAIL IS PART OF
THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
DETAIL “B”
16
9
0.305 ± 0.038
0.50
(.0197)
BSC
NO MEASUREMENT PURPOSE
4.039 ± 0.102
(.159 ± .004)
(NOTE 3)
(.0120 ± .0015)
TYP
0.280 ± 0.076
(.011 ± .003)
RECOMMENDED SOLDER PAD LAYOUT
16151413121110
9
REF
DETAIL “A”
0.254
(.010)
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
0° – 6° TYP
4.90 ± 0.152
(.193 ± .006)
GAUGE PLANE
0.53 ± 0.152
(.021 ± .006)
1 2 3 4 5 6 7 8
DETAIL “A”
0.86
(.034)
REF
1.10
(.043)
MAX
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 ± 0.0508
(.004 ± .002)
MSOP (MSE16) 0711 REV D
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL
NOT EXCEED 0.254mm (.010") PER SIDE.
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18
For more information www.linear.com/LT3799
LT3799
REVISION HISTORY
REV
DATE
01/12 Added “Maximum” to SENSE Current Limit Threshold parameter; Updated Conditions and Typ and Max values for
Dropout (V – INTV ) parameter; Changed Current Limit Typ value to 1±.
DESCRIPTION
PAGE NUMBER
A
3
IN
CC
Corrected Y-axis lables for G21, G22 and G23.
6
7
Reordered Pin Functions in numerical order.
Removed section title”Setting Control Voltages for LED Over Temperature and Brownout Conditions”.
02/16 Amended Current Limit Below Undervoltage Threshold
12
3
B
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
19
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LT3799
TYPICAL APPLICATION
Universal Input TRIAC Dimmable 14W LED Driver
L2
750µH
L1
39mH
BR1
R6
C1
47nF
C3
R7
90V
TO 265V
AC
D2
C5
20Ω
0.22µF
100k
R3
4:1:0.71
D4
R1
250Ω
R8
100k
C4
4.7pF
499k
C2
0.1µF
R2
250Ω
R4
499k
R13
2k
10µF
D3
R4
100k
0.5A
V
DCM
IN
V
FB
Z1
IN_SENSE
R15
5.90k
R5
3.48k
C10
390µF
× 2
LT3799
D1
R16
20Ω
V
REF
14W
Z2
R18
100k
R16
10k
R9
LED
CTRL3
CTRL2
CTRL1
GATE
POWER
40.2k
SENSE
R
INTV
CC
S
C9
4.7µF
0.10Ω
C8
2.2nF
PHOTOCELL
R17
10k
R10
23.2k
GND
+
–
FAULT
CT COMP
COMP
FAULT
3799 TA04
C7, 0.1µF
C6
0.1µF
BR1: DIODES, INC. HD06
D1: CENTRAL SEMICONDUCTOR CMR1U-06M
D2,D3: DIODES INC. BAV20W
D4:
Z1:
Z2:
T1:
DIODES INC. DFLS1150
FAIRCHILD SMBJ170A
CENTRAL SEMICONDUCTOR CMZ5938B
WÜRTH ELEKTRONIK WE750813144
M1: ST MICRO STD12N65M5
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
V : 4.±V to 40V, V
LT37±±/ LT37±±-1/ High Side 60V, 1MHz LED Controller with 3000:1
LT37±±-2 True Color PWM™ Dimming
= 60V, Dimming: 3000:1 True Color PWM,
IN
OUT(MAX)
OUT(MAX)
I
< 1µA, 3mm × 3mm QFN-16 and MSOP-16E Packages
SD
LT37±6/ LT37±6-1/ High Side 100V, 1MHz LED Controller with 3000:1
V : 6V to 100V, V
= 100V, Dimming: 3000:1 True Color PWM,
IN
LT37±6-2
True Color PWM Dimming
I
< 1µA, 3mm × 3mm QFN-16 and MSOP-16E Packages
SD
LT3743
Synchronous Step-Down 20A LED Driver with
Three-State LED Current Control
V : ±.±V to 36V, Dimming: 10000:1 True Color PWM, I < 1µA,
IN
SD
±mm × 8mm QFN-±2 Package
LT3±18
LT3±17
LT3741
2.3A, 2.±MHz High Current LED Driver with 3000:1
Dimming
V : 3V to 30V, Dimming: 3000:1 True Color PWM, I < 1µA,
IN
SD
4mm × 4mm QFN-16 Package
1.3A, 2.±MHz High Current LED Driver with 3000:1
Dimming
V : 3V to 30V, Dimming: 3000:1 True Color PWM, I < 1µA,
IN
SD
4mm × 4mm QFN-16 Package
High Power, Constant-Current, Constant-Voltage
Synchronous Step-Down Controller
V : 6V to 36V, Average Current Mode Control, I < 1µA,
IN SD
4mm × 4mm QFN-20 and TSSOP-20E Packages
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LT 0216 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 9±03±-7417
20
●
●
LINEAR TECHNOLOGY CORPORATION 2011
(408)432-1900 FAX: (408) 434-0±07 www.linear.com/LT3799
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