LT3799 Datasheet, PDF (1/20 Pages) Linear Technology – Offline Isolated Flyback LED Controller with Active PFC

Electrical Specifications Subject to Change
LT3799
Offline Isolated Flyback
LED Controller with Active PFC
FEATURES
n _{Isolated PFC LED Driver with Minimum Number of}
External Components
n _{TRIAC Dimmable}
n _{VIN and VOUT Limited Only by External Components}
n _{Active Power Factor Correction (Typical PFC > 0.97)}
n _{Low Harmonic Content}
n _{No Opto-Coupler Required}
n _{Accurate Regulated LED Current (±5% Typical)}
n _{Open LED and Shorted LED Protection}
n _{Thermally Enhanced 16-lead MSOP Package}
APPLICATIONS
n _{Offline 4W to 100W+ LED Applications}
n _{High DC VIN 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.
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.
TYPICAL APPLICATION
90V
TO 150V
AC
0.1µF
100k
FAULT
TRIAC Dimmable 20W LED Driver
0.22µF
100k
499k _100k
200Ω _499k
20Ω
4.7pF
10µF
2k
6.34k
V_IN
V_{IN_SENSE}
LT3799
DCM
FB
100k
4.99k
32.4k 40.2k
100k
NTC _16.2k
V_REF
CTRL3
CTRL2
CTRL1
GATE
SENSE
V_INTVCC
GND
FAULT CT COMP⁺ COMP^–
0.1µF
0.1µF
20Ω
4.7µF
4:1:1
1A
560µF
×2
0.05Ω
2.2nF
20W
LED
POWER
3799 TA01a
LED Current vs Input Voltage
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
90 100 110 120 130 140 150
V_IN (V_AC)
3799 TA01b
3799p
1