Electrical Specifications Subject to Change
LT3799
Offline Isolated Flyback
LED Controller with Active PFC
FEATURES
n
n
n
n
n
n
n
n
n
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.
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.
Isolated PFC LED Driver with Minimum Number of
External Components
TRIAC Dimmable
V
IN
and V
OUT
Limited Only by External Components
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
n
n
Offline 4W to 100W+ LED Applications
High DC V
IN
LED Applications
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
1.20
LED Current vs Input Voltage
90V
TO 150V
AC
0.22µF
0.1µF
200
499k
499k
100k
100k
20
4.7pF
10µF
V
IN
1.15
4:1:1
1.10
1.05
I
LED
(A)
2k
DCM
FB
100k
1A
1.00
0.95
0.90
0.85
V
IN_SENSE
6.34k
V
REF
100k
32.4k
40.2k
CTRL3
CTRL2
100k
NTC 16.2k
FAULT
CTRL1
LT3799
4.99k
560µF
×2
GATE
SENSE
V
INTVCC
20
20W
LED
POWER
0.05
0.80
90
100
110
120
130
V
IN
(V
AC
)
140
150
3799 TA01b
4.7µF
GND
FAULT
CT COMP
+
0.1µF
COMP
–
2.2nF
3799 TA01a
0.1µF
3799p
1
LINER [ LINEAR TECHNOLOGY ]
