JA4429 [Linear]
Offline Isolated Flyback LED Controller with Active PFC; 离线隔离型反激式LED控制器和Active PFC
| 型号： | JA4429 |
| 厂家： | 
Linear |
| 描述： | Offline Isolated Flyback LED Controller with Active PFC |
| 文件： | 总20页 (文件大小：1607K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Electrical Specifications Subject to Change
LT3799
Offline Isolated Flyback
LED Controller with Active PFC
FEATURES
DESCRIPTION
ꢀhe Lꢀ®3799 is an isolated flyback controller with power
factor correction specifically designed for driving LEDs.
ꢀhe 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 MOSFEꢀ. Utilizing an onboard
multiplier, the Lꢀ3799 typically achieves power factors
of 0.97. ꢀhe 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 ꢀypical)
Open LED and Shorted LED Protection
ꢀhermally Enhanced 16-lead MSOP Package
APPLICATIONS
ꢀhe Lꢀ3799 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
High DC V LED Applications
n
IN
L, Lꢀ, LꢀC, LꢀM, Linear ꢀechnology and the Linear logo are registered trademarks and
ꢀrue Color PWM is a trademark of Linear ꢀechnology 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
1.05
1.00
10µF
2k
DCM
1A
100k
V
IN
0.95
V
FB
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
V
INTVCC
0.05Ω
100k
NTC
4.7µF
16.2k
2.2nF
GND
–
+
FAULT
FAULT CT COMP COMP
3799 TA01a
0.1µF
0.1µF
3799p
1
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
GAꢀE, INꢀV ...........................................................18V
SENSE
GATE
CC
–
CꢀRL1, CꢀRL2, CꢀRL3, V
, COMP ................4V
V
17
GND
INTV
CC
NC
REF
IN_SENSE
FAULT
+
FB, Cꢀ, V
COMP ,...................................................3V
CT
REF,
V
IN
+
COMP
DCM
FB
SENSE......................................................................0.4V
DCM.......................................................................±3mA
Maximum Junction ꢀemperature .......................... 12±°C
Operating ꢀemperature Range (Note 2)
–
COMP
MSE PACKAGE
16-LEAD PLASTIC MSOP
= ±0°C/W, θ = 10°C/W
JC
EXPOSED PAD (PIN 17) IS GND, MUSꢀ BE SOLDERED ꢀO PCB
θ
JA
Lꢀ3799E ............................................ –40°C to 12±°C
Lꢀ3799I ............................................. –40°C to 12±°C
Storage ꢀemperature Range .................. –6±°C to 1±0°C
ORDER INFORMATION
LEAD FREE FINISH
Lꢀ3799EMSE#PBF
Lꢀ3799IMSE#PBF
TAPE AND REEL
PART MARKING*
3799
PACKAGE DESCRIPTION
TEMPERATURE RANGE
Lꢀ3799EMSE#ꢀRPBF
Lꢀ3799IMSE#ꢀRPBF
16-Lead Plastic MSOPE
16-Lead Plastic MSOPE
–40°C to 12±°C
–40°C to 12±°C
3799
Consult LꢀC Marketing for parts specified with wider operating temperature ranges. *ꢀhe 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
ꢀurn-On Voltage
V
V
ꢀurn-Off Voltage
12.3
10.7
2±.0
Hysteresis
V
– V
V
ꢀURNON
ꢀURNOFF
Shunt Regulator Voltage
Shunt Regulator Current Limit
Quiescent Current
I = 1mA
V
1±
±±
mA
Before ꢀurn-On
After ꢀurn-On
6±
70
7±
µA
µA
INꢀV Quiescent Current
Before ꢀurn-On
After ꢀurn-On
12
1.±
16
1.2
20.0
2.6
µA
mA
CC
V
V
V
ꢀhreshold
ꢀurn-Off
30
0
6±
90
mV
V
IN_SENSE
IN_SENSE
Linear Range
1.3
l
l
Voltage
0µA Load
200µA Load
1.97±
1.9±±±
2
1.98
2.02
2.02
V
V
REF
+
–
, CꢀRL1 = 1V, CꢀRL2 = 2V, CꢀRL3 = 2V
Error Amplifier Voltage Gain
∆V
/∆V
100
±0
V/V
COMP
COMP
Error Amplifier ꢀransconductance
∆I = ±µA
µmhos
3799p
2
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
±30
106
UNITS
nA
FB Pin Bias Current
(Note 3), FB = 1V
CꢀRL/CꢀRL2/CꢀRL3 = 1V
100
CꢀRL1/CꢀRL2/CꢀRL3 Pin Bias Current
SENSE Current Limit ꢀhreshold
SENSE Input Bias Current
Current Loop Voltage Gain
Cꢀ Pin Charge Current
nA
96
100
1±
mV
µA
Current Out of Pin, SENSE = 0V
+
–
∆V
/∆V
, 1000pF Cap from COMP to COMP
21
V/V
µA
CꢀRL
SENSE
10
Cꢀ Pin Discharge Current
Cꢀ Pin Low ꢀhreshold
200
240
1.2±
100
1.2±
4±
nA
Falling ꢀhreshold
Rising ꢀhreshold
mV
V
Cꢀ Pin High ꢀhreshold
Cꢀ Pin Low Hysteresis
mV
V
FB Pin High ꢀhreshold
1.22
1.29
DCM Current ꢀurn-On ꢀhreshold
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
INꢀV Regulation Voltage
9.8
10
±00
2±
10.4
900
V
mV
mA
mA
CC
Dropout (V – INꢀV
)
INꢀV = –10mA
CC
IN
CC
Current Limit
Current Limit
Gate Driver
Below Undervoltage ꢀhreshold
Above Undervoltage ꢀhreshold
17
80
120
t GAꢀE Driver Output Rise ꢀime
C = 3300pF, 105 to 905
20
20
ns
ns
V
r
L
t GAꢀE Driver Output Fall ꢀime
f
C = 3300pF, 905 to 105
L
GAꢀE Output Low (V
)
OL
0.0±
GAꢀE Output High (V
)
OH
INꢀV
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. ꢀhe
Lꢀ3799I is guaranteed to meet performance specifications from –40°C to
12±°C operating junction temperature.
Note 2: ꢀhe Lꢀ3799E 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
3799p
3
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)
SENSE Pin Threshold Current
vs Temperature
VREF vs Temperature
VREF vs VIN
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
3799p
4
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 TRAIC 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 (°C)
180
–50
0
25
50
75 100 125
0
60
90
150
–25
30
TEMPERATURE (°C)
TEMPERATURE (°C)
3799 G15
3799 G16
3799 G17
3799p
5
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
3799p
6
LT3799
PIN FUNCTIONS
V (Pin 11): Input Voltage. ꢀhis pin supplies current to
GATE (Pin 14): N-Channel MOSFEꢀ Gate Driver Output.
IN
the internal start-up circuitry and to the INꢀV LDO. ꢀhis
Switches between INꢀV and GND. ꢀhis pin is pulled to
CC
CC
pin must be locally bypassed with a capacitor. A 2±V shunt
regulator is internally connected to this pin.
GND during shutdown state.
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 Cꢀ pin
is high and the FB pin is higher than 1.2±V.
INTV (Pin 13): Regulated Supply for Internal Loads
CC
and GAꢀE Driver. Supplied from V and regulates to 10V
IN
(typical). INꢀV must be bypassed with a 4.7µF capacitor
CC
placed close to the pin.
CT (Pin 6): ꢀimer 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 Cꢀ pin reaches 1.2±V.
If a fault is detected, the controller will stop switching and
begintodischargetheCꢀcapacitorwitha200nApull-down
current. When the pin reaches 240mV, the controller will
start to switch again.
+
–
COMP , COMP (Pin 7, Pin 8): Compensation Pins for
InternalErrorAmplifier.Connectacapacitorbetweenthese
two pins to compensate the internal feedback loop.
DCM(Pin10):DiscontinuousConductionModeDetection
Pin. Connect a capacitor and resistor in series with this
pin to the third winding.
V
(Pin16):LineVoltageSensePin.ꢀhepinisused
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. ꢀhe voltage on this pin should
be between 1.2±V to 1.±V at the maximum input voltage.
FAULT (Pin 5): Fault Pin. An open-collector pull-down on
FAULT asserts if FB is greater than 1.2±V with the Cꢀ pin
higher than 1.2±V.
V
(Pin 4): Voltage Reference Output Pin, ꢀypically 2V.
REF
CTRL1,CTRL2,CTRL3(Pin1,Pin2,Pin3):CurrentOutput
Adjustment Pins. ꢀhese pins control the output current.
ꢀhe lowest value of the three CꢀRL inputs is compared to
the negative input of the operational amplifier. Due to the
unique nature of the Lꢀ3799 control loop, the maximum
ꢀhis pin drives a resistor divider for the CꢀRL pin, either
foranalogdimmingorfortemperaturelimit/compensation
of LED load. Can supply up to 200µA.
GND (Exposed Pad Pin 17): Ground. ꢀhe exposed pad
of the package provides both electrical contact to ground
and good thermal contact to the printed circuit board.
ꢀhe exposed pad must be soldered to the circuit board
for proper operation.
currentdoesnotdirectlycorrespondtotheV
voltages.
CꢀRL
SENSE (Pin 15): ꢀhe 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 MOSFEꢀ. ꢀhe negative terminal of the
current sense resistor should be connected to the GND
plane close to the IC.
3799p
7
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
M1
14
15
17
Q
SW1
C6
1M
A5
MASTER
LATCH
COMP
A4
8
1
2
3
4
R6
CTRL1
CTRL2
CTRL3
–
+
+
+
A6
LOW OUTPUT
MULTIPLIER
CURRENT
OSCILLATOR
V
REF
3799 BD
3799p
8
LT3799
OPERATION
ꢀhe Lꢀ3799 is a current mode switching controller IC
designed specifically for generating an average current
outputinanisolatedflybacktopology.ꢀhespecialproblem
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. ꢀhe Lꢀ3799
uses a novel method of using the external MOSFEꢀs 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.
pin with 10µA. Once the Cꢀ pin reaches 340mV, switching
begins. ꢀhe V pin has 10.7V of hysteresis to allow for
IN
plenty of flexibility with the input and output capacitor
values. ꢀhe 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
MOSFEꢀ on and a current flows through the primary
winding. ꢀhis current increases at a rate proportional
to the input voltage and inversely proportional to the
magnetizing inductance of the transformer. ꢀhe 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. ꢀhis 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. ꢀhe capacitor
connected to the DCM pin, C1, trips the comparator, A2,
which serves as a dv/dt detector, when the ringing occurs.
ꢀhis timing information is used to calculate the output
current (description to follow). ꢀhe dv/dt detector waits
for the ringing waveform to reach its minimum value and
then the switch turns back on. ꢀhis 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).
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. ꢀhe Lꢀ3799
modulates the peak current limit with a scaled version of
the input voltage. ꢀhis technique provides power factors
of 0.97 or greater.
ꢀhe Block Diagram shows an overall view of the system.
ꢀhe external components are in a flyback topology con-
figuration. ꢀhe third winding senses the output voltage
and also supplies power to the part in steady-state opera-
tion. ꢀhe V pin supplies power to an internal LDO that
IN
generates10VattheINꢀV pin.ꢀhenovelcontrolcircuitry
CC
consists of an error amplifier, a multiplier, a transmission
gate, a current comparator, a low output current oscillator
and a master latch, which will be explained in the follow-
ing sections. ꢀhe 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.
ꢀhe part features a 1.9A gate driver.
ꢀhe Lꢀ3799 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. ꢀhe internal
Primary-Side Current Control Loop
ꢀhe CꢀRL1/CꢀRL2/CꢀRL3 pins control the output current
of the flyback controller. ꢀo simplify the loop, assume
the V
pin is held at a constant voltage above
IN_SENSE
LDO starts to supply current to the INꢀV when V is
CC
IN
1V, eliminating the multiplier from the control loop. ꢀhe
error amplifier, A±, is configured as an integrator with
above 23V. ꢀhe V and INꢀV capacitors are charged by
IN
CC
the current from R3. When V exceeds 23V and INꢀV is
IN
CC
+
the external capacitor, C6. ꢀhe COMP node voltage is
in regulation at 10V, the part will began to charge the Cꢀ
3799p
9
LT3799
OPERATION
ing the rest of the cycle. ꢀhe equation for expressing the
output current is:
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.
ꢀhe output of the multiplier controls the peak current with
its connection to the current comparator, A1. ꢀhe output
of the multiplier is also connected to the transmission
gate, SW1. ꢀhe transmission gate, SW1, turns on when
the secondary current flows to the output capacitor. ꢀhis
is called the flyback period (when the output diode D1 is
on). ꢀhe current through the 1M resistor gets integrated
byA±. ꢀhelowestCꢀRLinputisequaltothenegativeinput
of A± in steady state.
I
= 0.5 • I • N • D
PK
OUꢀ
whereDisequaltothepercentageofthecyclerepresented
by the flyback time.
ꢀhe Lꢀ3799 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.
ꢀhe integrator adjusts the peak current until the calculated
output current equals the control voltage. If the calculated
outputcurrentislowcomparedtothecontrolpin,theerror
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 Lꢀ3799 calculates it using the
informationavailableontheprimarysideofthetransformer.
ꢀheoutputcurrentmaybecalculatedbytakingtheaverage
oftheoutputdiodecurrent.AsshowninFigure1,thediode
current is a triangle waveform with a base of the flyback
time and a height of the peak secondary winding 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 current and zero dur-
+
amplifier increases the voltage on the COMP node, thus
increasing the current comparator input.
When the V
voltage is connected to a resistor
IN_SENSE
divider of the supply voltage, the current limit is propor-
+
tional to the supply voltage if COMP is held constant.
ꢀhe output of the error amplifier is multiplied with the
V
pin voltage. If the Lꢀ3799 is configured with a
IN_SENSE
fast control loop, slower changes from the V
pin
IN_SENSE
willnotinterferewiththecurrentlimitortheoutputcurrent.
+
ꢀheCOMP pinwilladjusttothechangesoftheV
.
IN_SENSE
ꢀhe only way for the multiplier to function properly is to
set the control loop to be an order of magnitude slower
thanthefundamentalfrequencyoftheV
signal. In
IN_SENSE
the offline case, the fundamental frequency of the supply
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
SWITCH
WAVEFORM
TRIAC Dimming Features
ꢀhe Lꢀ3799 incorporates some special features that aid in
thedesignofanofflineLEDcurrentsourcewhenusedwith
a ꢀRIAC dimmer. ꢀRIAC dimmers are not ideal switches
when turned off and allow milliamps of current to flow
through them. ꢀhis is an issue if used with a low quiescent
partsuchastheLꢀ3799.Insteadofturningthemainpower
3799p
T
FLYBACK
3799 F01
T
PERIOD
Figure 1. Secondary Diode Current and Switch Waveforms
10
LT3799
OPERATION
MOSFEꢀ off when the ꢀRIAC is off, this power device is
kept on and sinks the current to properly load the ꢀRIAC.
When the ꢀRIAC turns on, the V
andenablestheloop, butthecurrentcomparatorisalways
Programming Output Current
ꢀhe maximum output current depends on the supply
voltage and the output voltage in a flyback topology.
pin detects this
IN_SENSE
With the V
pin connected to 1V and a DC supply
IN_SENSE
enabled and turns the switch off if it is tripped.
voltage, the maximum output current is determined at
the minimum supply voltage, and the maximum output
voltage using the following equation:
Start-Up
ꢀhe Lꢀ3799 uses a hysteretic start-up to operate from
high offline voltages. A resistor connected to the supply
voltage protects the part from high voltages. ꢀhis resis-
N
IOUꢀ(MAX) = 2 •(1− D) •
42 •RSENSE
tor is connected to the V pin on the part and also to a
IN
where
capacitor.Whentheresistorchargesthepartupto23Vand
VOUꢀ •N
VOUꢀ •N + V
INꢀV isinregulationat10V, thepartbeginstochargethe
D =
CC
IN
Cꢀ pin to 340mV and then starts to switch. ꢀhe resistor
does not provide power for the part in steady state, but
relies on the capacitor to start-up the part, then the third
ꢀhe maximum control voltage to achieve this maximum
output current is 2V • (1-D).
winding begins to provide power to the V pin along with
IN
the resistor. An internal voltage clamp is attached to the
It is suggested to operate at 9±5 of these values to give
margin for the part’s tolerances.
V pin to prevent the resistor current from allowing V
IN
IN
to go above the absolute maximum voltage of the pin.
ꢀhe internal clamp is set at 2±V and is capable of 28mA
(typical) of current at room temperature. But, ideally, the
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:
resistor connected between the input supply and the V
IN
pin should be chosen so that less than 10mA is being
shunted by this internal clamp.
CT Pin and Faults
ꢀhe Cꢀ pin is a timing pin for the fault circuitry. When the
input voltages are at the correct levels, the Cꢀ pin sources
10µA of current. When the Cꢀ pin reaches 340mV, the part
begins to switch. ꢀhe output voltage information from the
FB pin is sampled but ignored until the Cꢀ pin reaches
1.2±V. When this occurs, if the FB pin is above 1.2±V, the
fault flag pulls low. ꢀhe FAULT pin is meant to be used
N
IOUꢀ(MAX) = (1− D) •
• 47.±5
42 •RSENSE
where
D =
VOUꢀ •N
VOUꢀ •N + V
IN
with a large pull-up resistor to the INꢀV pin or another
CC
ꢀhe maximum control voltage to achieve this maximum
output current is (1-D) • 47.5%.
supply. ꢀhe Cꢀ pin begins to sink 200nA of current. When
the Cꢀ pin goes below 240mV, the part will re-enable itself,
begin to switch, and start to source 10µA of current to the
Cꢀ pin but not remove the fault condition. When the Cꢀ
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
IOUꢀ = CꢀRL •
42 •RSENSE
3799p
11
LT3799
OPERATION
ꢀhe V
pin supplies a 2V reference voltage to be used
with AC, the following equation should be used with the
correction factor:
REF
with the control pins. ꢀo set an output current, a resistor
divider is used from the 2V reference to one of the control
pins. ꢀhe following equation sets the output current with
a resistor divider:
N
IOUꢀ = CꢀRL •
42 •RSENSE − CF
2N
2N
• RSENSE
R1= R2
− 1
R1= R2
− 1
(42 • I
• RSENSE • CF)
OUꢀ
42 • I
OUꢀ
where CR is the output current correction factor on the
Y-axis in Figure 3.
where R1 is the resistor connected to the V pin and the
CꢀRL pin and R2 is the resistor connected to the CꢀRL
REF
pin and ground.
Setting Control Voltages for LED Over Temperature
and Brownout Conditions
When used with an AC input voltage, the Lꢀ3799 senses
when the V
goes below 6±mV and above 6±mV
IN_SENSE
Critical Conduction Mode Operation
for detecting when the ꢀRIAC is off. During this low input
voltagetime,theoutputcurrentregulationloopisoffbutthe
partstillswitches.ꢀhishelpswithoutputcurrentregulation
with a ꢀRIAC but introduces a line regulation error. When
Criticalconductionmodeisavariablefrequencyswitching
scheme that always returns the secondary current to zero
with every cycle. ꢀhe Lꢀ3799 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. ꢀhe DCM pin
uses a fast current input comparator in combination with
a small capacitor to detect dv/dt on the third winding. ꢀo
eliminate false tripping due to leakage inductance ringing,
V
is low, very little power is being delivered to
IN_SENSE
the output and since the output current regulation loop
is off, this time period needs to be accounted for in set-
ting the output current. ꢀhis time period slightly varies
with line voltage. Figure 2 shows the correction factor
in selecting the resistor divider resistors. When used
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
0.5
PEAK V
1
1.5
0
IN_SENSE
3799 F03
Figure 2. Correction Factor in Selecting the
Resistor Divider Resistors
Figure 3. Output Current Correction Factor
3799p
12
LT3799
OPERATION
a blanking time of between 600ns and 2.2±µs is applied
after the switch turns off, depending on the current limit
shown in the Leakage Inductance Blanking ꢀime vs Cur-
rentLimitcurveintheꢀypicalPerformanceCharacteristics
section. ꢀhe detector looks for 40µA of current through
the DCM pin due to falling voltage on the third winding
when the secondary diode turns off. ꢀhis detection is
important since the output current is calculated using this
comparator’s output. ꢀhis is not the optimal time to turn
the switch on because the switch voltage is still close to
where
VOUꢀ •N
VOUꢀ •N + V
D =
IN
Minimum Current Limit
ꢀhe Lꢀ3799 features a minimum current limit of approxi-
mately75ofthepeakcurrentlimit.ꢀhisisnecessarywhen
operating in critical conduction mode since low current
limits would increase the operating frequency to a very
highfrequency.ꢀheoutputvoltagesensingcircuitryneeds
a minimum amount of flyback waveform time to sense the
output voltage on the third winding. ꢀhe time needed is
3±0ns.ꢀheminimumcurrentlimitallowstheuseofsmaller
transformers since the magnetizing primary inductance
does not need to be as high to allow proper time to sample
the output voltage information.
V + V
• N and would waste all the energy stored in the
IN
OUꢀ
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. ꢀhis is a second-
order network composed of the parasitic capacitance on
the switch node and the magnetizing inductance of the
primary winding of the transformer. ꢀhe minimum volt-
age of the switch node during this discontinuous ring is
Errors Affecting Current Output Regulation
V
– V
• N. The LT3799 turns the switch back on at
IN
OUꢀ
ꢀhereareafewfactorsaffectingtheregulationofcurrentin
amanufacturingenvironmentalongwithsomesystematic
issues. ꢀhe main manufacturing issues are the winding
turns ratio and the Lꢀ3799 control loop accuracy. ꢀhe
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. ꢀhe 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.
this time, during the discontinuous switch waveform, by
sensing when the slope of the switch waveform goes from
negativetopositiveusingthedv/dtdetector.ꢀhisswitching
technique may increase efficiency by ±5.
Sense Resistor Selection
ꢀhe resistor, R , between the source of the external
SENSE
N-channelMOSFEꢀandGNDshouldbeselectedtoprovide
anadequateswitchcurrenttodrivetheapplicationwithout
exceeding the current limit threshold .
For applications without power factor correction, select a
resistor according to:
2(1− D)N
IOUꢀ • 42
RSENSE
=
• 9±5
ꢀhereareanumberofsystematicoffsetsthatmaybeelimi-
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. ꢀhis error may be com-
where
D =
VOUꢀ •N
VOUꢀ •N + V
IN
For applications with power factor correction, select a
resistor according to:
(1− D)N
IOUꢀ • 42
RSENSE
=
• 47.±5
pensated for at the primary supply voltage, but this does
3799p
13
LT3799
OPERATION
notsolvetheproblemcompletelyforothersupplyvoltages.
Another systematic error is that the current comparator
cannot instantaneously turn off the main power device.
ꢀhis delay time leads to primary current overshoot. ꢀhis
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. ꢀhe overshoot is proportional to the supply voltage,
so again this affects the line regulation.
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
sideMOSFEꢀ’ssuperiorperformanceasaswitch.Ahigher
NPSdoesreducethevoltagestressonthesecondary-side
diode while increasing the voltage stress on the primary-
side MOSFEꢀ. If switching frequency at full output load is
kept constant, the amount of energy delivered per cycle by
the transformer also stays constant regardless of the N .
PS
Universal Input
ꢀherefore, the size of the transformer remains the same at
practical N ’s. Adjusting the turns ratio is a good way to
PS
ꢀhe Lꢀ3799 operates over the universal input range of
find an optimal MOSFEꢀ and diode for a given application.
90V to 26±V . Output current regulation error may
AC
AC
be minimized by using two application circuits for the
Switch Voltage Clamp Requirement
wide input range: one optimized for 120V and another
AC
optimized for 220V . ꢀhe first application pictured in
Leakage inductance of an offline transformer is high due
to the extra isolation requirement. ꢀhe leakage inductance
energy is not coupled to the secondary and goes into
the drain node of the MOSFEꢀ. ꢀhis is problematic since
400V and higher rated MOSFEꢀs cannot always handle
this energy by avalanching. ꢀherefore the MOSFEꢀ needs
protection. A transient voltage suppressor (ꢀVS) and
diode are recommended for all offline application and
connected, as shown in Figure 4. ꢀhe ꢀVS device needs
AC
the ꢀypical Applications section shows three options:
universal input, 120V , and 220V . ꢀhe circuit varies by
AC
AC
threeresistors.IntheꢀypicalPerformanceCharacteristics
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
a reverse breakdown voltage greater than (V
+ V )*N
OUꢀ
f
where V
is the output voltage of the flyback converter,
duty cycle low, lower N , at the maximum input voltage
OUꢀ
PS
V is the secondary diode forward voltage, and N is the
since thedutycycle willincrease when the ACwaveformis
f
turns ratio.
decreases to zero volts. A higher N increases the output
PS
V
SUPPLY
GATE
3799 F04
Figure 4. Clamp
3799p
14
LT3799
OPERATION
Transformer Design Considerations
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.
ꢀransformer specification and design is a critical part of
successfully applying the Lꢀ3799. 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
betightlycontrolledtoensureaconsistentoutputcurrent.
In non-PFC applications, the crossover frequency may
be increased to improve transient performance. ꢀhe
desired crossover frequency needs to be set an order
of magnitude below the switching frequency for optimal
performance.
MOSFET and Diode Selection
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 ꢀechnology has worked
with several leading magnetic component manufacturers
to produce predesigned flyback transformers for use with
the Lꢀ3799. ꢀable 1 shows the details of several of these
transformers.
With a strong 1.9A gate driver, the Lꢀ3799 can effectively
drive most high voltage MOSFEꢀs. A low Q MOSFEꢀ is
g
recommendedtomaximizeefficiency.Inmostapplications,
the R
should be chosen to limit the temperature rise
DS(ON)
of the MOSFEꢀ. ꢀhe drain of the MOSFEꢀ is stressed to
• N + V during the time the MOSFEꢀ is off and
V
OUꢀ
PS
IN
the secondary diode is conducting current. But in most
applications,theleakageinductancevoltagespikeexceeds
this voltage. ꢀhe voltage of this stress is determined
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 MOSFEꢀ. A transient voltage suppressor and diode
are slower than the leakage inductance voltage spike,
therefore causing a higher voltage than calculated.
Loop Compensation
ꢀhe current output feedback loop is an integrator con-
figuration with the compensation capacitor between the
negative input and output of the operational amplifier.
ꢀhis is a one-pole system therefore a zero is not needed
in the compensation. For offline applications with PFC,
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
3799p
15
LT3799
OPERATION
ꢀhe secondary diode stress may be as much as
Protection from Open LED and Shorted LED Faults
V
OUꢀ
+ 2 • V /N due to the anode of the diode ringing
IN PS
ꢀheLꢀ3799detectsoutputovervoltageconditionsbylook-
ing at the voltage on the third winding. ꢀhe 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 Cꢀ 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 “Cꢀ Pin and Faults” in the Operation section.
ꢀhis 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. ꢀhe 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.
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
+ V /N .
OUꢀ
IN PS
With a high N and output current greater than 3A, the
PS
I
through the diode can become very high and a low
forward drop Schottky is recommended.
RMS
Discontinuous Mode Detection
ꢀhe 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 INꢀV to the DCM pin adds this current. Up to
CC
an additional 100µA of current may be needed in some
cases. ꢀhe DCM pin is roughly 0.7V, therefore the resistor
value is selected using the following equation:
During a shorted LED condition, the Lꢀ3799 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
ꢀhis causes the part’s V UVLO to shutdown switching.
IN
where I is equal to the additional current into the DCM pin.
ꢀhe part starts switching again when V has reached its
IN
turn-on voltage.
Power Factor Correction/Harmonic Content
ꢀhe Lꢀ3799 attains high power factor and low harmonic
content by making the peak current of the main power
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, Lꢀ3799 applications meet
IEC 6100-3-2 Class C harmonic standards.
3799p
16
LT3799
TYPICAL APPLICATIONS
Universal TRIAC Dimmable 20W LED Driver
L2
800µH
L1
33mH
BR1
R6
C3
C1
0.1µF
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
4.99k
R5
3.48k
C10
560µF
× 2
LT3799
D1
R16
20Ω
V
REF
20W
Z2
R18
100k
R16
R9
LED
CTRL3
CTRL2
CTRL1
GATE
M1
32.4k
40.2k
POWER
SENSE
R
S
V
INTVCC
100k
NTC
C9
4.7µF
0.05Ω
C8
2.2nF
R10
24.9k
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 CMZ5938B
COILCRAFT JA4429-AL
M1: FAIRCHILD FDPF15N65
Component Values for Input Voltage Ranges
R5 (Ω)
6.34k
3.48k
3.48k
R10 (Ω)
R (Ω)
R1 (Ω)
C2 (µF)
0.1
C3 (µF)
0.22
S
Optimized for 110V
Optimized for 220V
Universal
16.2k
0.0±
200
1.00k
200
24.9k
0.07±
0.0±
0.033
0.1
0.1
1±.4k
0.22
3799p
17
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
V
INTVCC
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
3799p
18
LT3799
PACKAGE DESCRIPTION
MSE Package
16-Lead Plastic MSOP, Exposed Die Pad
(Reference LꢀC DWG # 0±-08-1667 Rev A)
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° – 6° TYP
0.254
(.010)
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
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) 0608 REV A
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
3799p
Information furnished by Linear ꢀechnology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear ꢀechnology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
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
V
S
INTVCC
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
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SD
4mm × 4mm QFN-16 Package
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3799p
LT 0211 • 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
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