LT1249

1

Power Factor Controller

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Standard 8-Pin Packages

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High Power Factor Over Wide Load Range

with Line Current Averaging

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International Operation Without Switches

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Instantaneous Overvoltage Protection

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Minimal Line Current Dead Zone

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Typical 250

µA Start-Up Supply Current

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Rejects Line Switching Noise

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Synchronization Capability

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Low Quiescent Current: 9mA

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Fast 1.5A Peak Current Gate Driver

The 8-pin LT

tion for universal offline power systems with very few

external parts. By using fixed high frequency PWM current

averaging without the need for slope compensation, the

LT1249 achieves far lower line current distortion, with a

smaller magnetic element than systems that use either peak

current detection or zero current switching approach, in

both continuous and discontinuous modes of operation.

The LT1249 uses a multiplier containing a square gain

function from the voltage amplifier to reduce the AC gain

at light output load and thus maintains low line current

distortion and high system stability. The LT1249 also

provides filtering capability to reject line switching noise

which can cause instability when fed into the multiplier.

Line current dead zone is minimized with low bias voltage

at the current input to the multiplier.

The LT1249 provides many protection features including

peak current limiting and overvoltage protection. The

switching frequency is internally set at 100kHz.

While the LT1249 simplifies PFC design with minimal

parts count, the LT1248 provides flexibilities in switching

frequency, overvoltage and current limit.

–

+

–

+

–

+

–

+

–

+

200

7.5V

44

µA

22

µA

15

µA

1V

EA

–

+

32k

20

µA

250

µA MAX

7.5V

0.7V

OSC

R

S

Q

6

4

5

32

1

7

8

35pF

4k

4k

16V/10V

CA

MULTIPLIER

RUN

RUN

16V

GND

GTDR

1249 BD

SYNC

M1

, LTC and LT are registered trademarks of Linear Technology Corporation.

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Universal Power Factor Corrected Power Supplies

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Preregulators up to 1500W

FEATURES

DESCRIPTIO

APPLICATIO S

BLOCK DIAGRA