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.
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Isolated PFC LED Driver with Minimum Number of
External Components
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TRIAC Dimmable
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V and V
Limited Only by External Components
IN
OUT
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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.
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Offline 4W to 100W+ LED Applications
High DC V LED Applications
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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