UC1854 UC2854 UC3854 High Power Factor Preregulator FEATURES DESCRIPTION * Control Boost PWM to 0.99 Power Factor * Limit Line Current Distortion To <5% * World-Wide Operation Without Switches * Feed-Forward Line Regulation * Average Current-Mode Control * Low Noise Sensitivity * The UC1854 provides active power factor correction for power systems that otherwise would draw non-sinusoidal current from sinusoidal power lines. This device implements all the control functions necessary to build a power supply capable of optimally using available power-line current while minimizing line-current distortion. To do this, the UC1854 contains a voltage amplifier, an analog multiplier/divider, a current amplifier, and a fixed-frequency PWM. In addition, the UC1854 contains a power MOSFET compatible gate driver, 7.5V reference, line anticipator, load-enable comparator, low-supply detector, and over-current comparator. Low Start-Up Supply Current * Fixed-Frequency PWM Drive * Low-Offset Analog Multiplier/Divider * 1A Totem-Pole Gate Driver * Precision Voltage Reference BLOCK DIAGRAM The UC1854 uses average current-mode control to accomplish fixedfrequency current control with stability and low distortion. Unlike peak current-mode, average current control accurately maintains sinusoidal line current without slope compensation and with minimal response to noise transients. The UC1854's high reference voltage and high oscillator amplitude minimize noise sensitivity while fast PWM elements permit chopping frequencies above 200kHz. The UC1854 can be used in single and three phase systems with line voltages that vary from 75 to 275 volts and line frequencies across the 50Hz to 400Hz range. To reduce the burden on the circuitry that supplies power to this device, the UC1854 features low starting supply current. These devices are available packaged in 16-pin plastic and ceramic dual in-line packages, and a variety of surface-mount packages. UDG-92055 6/98 UC1854 UC2854 UC3854 ABSOLUTE MAXIMUM RATINGS Supply Voltage VCC . . . . . . . . . . . . . . . . . . . . GT Drv Current, Continuous . . . . . . . . . . . . . GT Drv Current, 50% Duty Cycle. . . . . . . . . . Input Voltage, VSENSE, VRMS . . . . . . . . . . . . . Input Voltage, ISENSE, Mult Out . . . . . . . . . . . Input Voltage, PKLMT . . . . . . . . . . . . . . . . . . Input Current, RSET, IAC , PKLMT, ENA . . . . . Power Dissipation . . . . . . . . . . . . . . . . . . . . . Storage Temperature . . . . . . . . . . . . . . . Lead Temperature (Soldering, 10 Seconds) . . . . . . . . . . . . . . . . . 35V . . . . . . . . . . . . . . . 0.5A . . . . . . . . . . . . . . . 1.5A . . . . . . . . . . . . . . . . 11V . . . . . . . . . . . . . . . . 11V . . . . . . . . . . . . . . . . . 5V . . . . . . . . . . . . . . 10mA . . . . . . . . . . . . . . . . 1W . . . . . -65oC to +150oC . . . . . . . . . . . . . +300oC Note 1: All voltages with respect to Gnd (Pin 1). Note 2: All currents are positive into the specified terminal. Note 3: ENA input is internally clamped to approximately 14V. Note 4: Consult Unitrode Integrated Circuits databook for information regarding thermal specifications and limita- CONNECTION DIAGRAMS DIL-16 & SOIC-16 (Top View) J, N & DW Packages PLCC-20 & LCC-20 (Top View) Q & L Packages PACKAGE PIN FUNCTION FUNCTION PIN N/C Gnd PKLMT CA Out ISENSE N/C Mult Out IAC VA Out VRMS N/C VREF ENA VSENSE RSET N/C SS CT VCC GT Drv 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Unless otherwise stated, VCC=18V, RSET=15k to ground, CT=1.5nF to ground, PKLMT=1V, ENA=7.5V, ELECTRICAL CHARACTERISTICS VRMS=1.5V, IAC=100A, ISENSE=0V, CA Out=3.5V, VA Out=5V, VSENSE =7.5V, no load on SS, CA Out, VA Out, REF, GT Drv, -55oC