LT1249 Power Factor Controller FEATURES DESCRIPTIO n Standard 8-Pin Packages The 8-pin LT 1249 provides active power factor correc- n High Power Factor Over Wide Load Range tion for universal offline power systems with very few with Line Current Averaging external parts. By using fixed high frequency PWM current n International Operation Without Switches averaging without the need for slope compensation, the n Instantaneous Overvoltage Protection LT1249 achieves far lower line current distortion, with a n Minimal Line Current Dead Zone smaller magnetic element than systems that use either peak n Typical 250m A Start-Up Supply Current current detection or zero current switching approach, in n Rejects Line Switching Noise both continuous and discontinuous modes of operation. n Synchronization Capability The LT1249 uses a multiplier containing a square gain n Low Quiescent Current: 9mA function from the voltage amplifier to reduce the AC gain n Fast 1.5A Peak Current Gate Driver at light output load and thus maintains low line current distortion and high system stability. The LT1249 also U provides filtering capability to reject line switching noise APPLICATIO S which can cause instability when fed into the multiplier. n Universal Power Factor Corrected Power Supplies Line current dead zone is minimized with low bias voltage n Preregulators up to 1500W 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 , LTC and LT are registered trademarks of Linear Technology Corporation. frequency, overvoltage and current limit. BLOCK DIAGRA CA VA M GND V OUT OUT CC OUT 32 1 7 5 7.5V V REF R MOUT + 7.5V V SENSE 4k + EA V RUN CC 6 I A 250m A MAX 16V/10V MULTIPLIER I M 2 I 32k AC I I + A B I I = B M 2 CA 4 200m A R Q + GTDR S 15m A + g = 1/3k RUN m 8 1V + 0.7V M1 OSC + SYNC 4k 16V 44m A 20m A 22m A 35pF 1249 BD 1 W ULT1249 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION Supply Voltage ....................................................... 27V ORDER PART GTDR Current Continuous ..................................... 0.5A TOP VIEW NUMBER GTDR Output Energy (Per Cycle) ............................. 5m J GND 1 8 GTDR I Input Current ................................................. 20mA LT1249CN8 AC CA 2 7 V OUT CC LT1249IN8 V Input Voltage ............................................ V SENSE MAX M 3 V 6 OUT SENSE LT1249CS8 M Input Current.............................................. 5mA OUT I 4 5 VA AC OUT LT1249IS8 Operating Junction Temperature Range N8 PACKAGE LT1249C ................................................ 0 C to 100 C 8-LEAD PDIP S8 PART S8 PACKAGE LT1249I ........................................... 40 C to 125 C 8-LEAD PLASTIC SO MARKING Thermal Resistance (Junction-to-Ambient) T = 125 C, q = 100 C/W (N8) JMAX JA N8 Package ................................................ 100 C/W 1249 T = 125 C, q = 120 C/W (S8) JMAX JA S8 Package................................................. 120 C/W 1249I Storage Temperature Range ..................65 C to 150 C Consult factory for Military grade parts. Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the operating temperature range, otherwise specifications are at T = 25 C. Maximum operating voltage (V ) = 25V, V = 18V, I = 100m A, CA = 3.5V, A MAX CC AC OUT VA = 5V, no load on any outputs, unless otherwise noted. OUT PARAMETER CONDITIONS MIN TYP MAX UNITS Overall Supply Current (V in Undervoltage Lockout) V = Lockout Voltage 0.2V l 0.25 0.45 mA CC CC Supply Current, On 11.5V V V , CA = 1V l 912 mA CC MAX OUT V Turn-On Threshold l 15.5 16.5 17.5 V CC V Turn-Off Threshold l 9.5 10.5 11.5 V CC Voltage Amplifier V Bias Current V = 0V to 7V l 25 250 nA SENSE SENSE Voltage Amp Gain 70 100 dB Voltage Amp Unity-Gain Bandwidth 1.5 MHz Voltage Amp Output High 0 Source Current 50m A l 10 12 V Voltage Amp Output Low 0 Sink Current 5m A l 0.1 0.4 V Voltage Amp Source Current l 130 260 450 m A Voltage Amp Sink Current Threshold Linear Operation, 2V < VA < 10V l 33 44 57 m A OUT Voltage Amp Sink Current Hysteresis 2V < VA < 10V l 14 22.5 30 m A OUT Current Amplifier Current Amp Offset Voltage l 2 15 mV Current Amp Transconductance D I = 40m A l 150 320 550 m mho CAOUT Current Amp Voltage Gain 2.5V V 7.5V 500 1000 V/V CAOUT Current Amp Source Current V = 1V, I = 0m A 100 145 220 m A MOUT M Current Amp Sink Current V = 0.3V, I = 0m A 67 95 125 m A MOUT M Current Amp Output High 7.4 8.1 V Current Amp Output Low 1.2 2 V 2 U W U U WWW