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| LT3798_15 Datasheet, PDF (1/20 Pages) Linear Technology – Isolated No Opto-Coupler Flyback Controller with Active PFC | |||
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FEATURES
n Isolated PFC Flyback with Minimum Number of
External Components
n VIN and VOUT Limited Only by External Components
n Active Power Factor Correction
n Low Harmonic Distortion
n No Opto-Coupler Required
n Constant-Current and Constant-Voltage Regulation
n Accurate Regulated Voltage and Current (±5% Typical)
n Energy Star Compliant (<0.5W No Load Operation)
n Thermally Enhanced 16-lead MSOP Package
APPLICATIONS
n Offline 5W to 100W+ Applications
n High DC VIN Isolated Applications
n Offline Bus Converter (12V, 24V or 48V Outputs)
LT3798
Isolated No Opto-Coupler
Flyback Controller
with Active PFC
DESCRIPTION
The LT®3798 is a constant-voltage/constant-current iso-
lated flyback controller that combines active power factor
correction (PFC) with no opto-coupler required for output
voltage feedback into a single-stage converter. A LT3798
based design can achieve a power factor of greater than 0.97
by actively modulating the input current, allowing compli-
ance with most Harmonic Current Emission requirements.
The LT3798 is well suited for a wide variety of off-line
applications. The input range can be scaled up or down,
depending mainly on the choice of external components.
Efficiencies higher than 86% can be achieved with output
power levels up to 100W. In addition, the LT3798 can easily
be designed into high DC input applications.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5438499 and 7471522.
TYPICAL APPLICATION
Universal Input 24W PFC Bus Converter
90V
TO 265V
AC
499k
0.1µF 499k
1M
95.3k
100k 40.2k
221k 16.5k
100k
D2 20Ω
100k
D3
4.7pF
10µF
2k
VIN
VIN_SENSE
EN/UVLO
DCM
FB
LT3798
VREF
CTRL3
GATE
CTRL2
SENSE
CTRL1
OVP
VC
INTVCC
GND
COMP+ COMPâ
2.2µF 0.1µF
90.9k
4.99k
22pF
20Ω
4.7µF
4:1:1
D4
Z1
560µF
D1
Ã2
0.05Ω
2.2nF
24V
1A
Z2
3798 TA01a
VOUT vs IOUT
24.50
24.25
24.00
23.75
23.50
0
VAC = 90V
VAC = 120V
VAC = 220V
VAC = 265V
0.2 0.4 0.6 0.8
1
IOUT (A)
3798 TA01b
3798fa
1
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