UC1854B| Datasheet

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UC1854A UC2854A, UC2854B UC3854A, UC3854B
SLUS329E MONTH 2003 REVISED JANUARY 2008

ADVANCED HIGH-POWER FACTOR PREREGULATOR
1

FEATURES
Controls Boost PWM to Near-Unity Power Factor Limits Line Current Distortion To <3% World-Wide Operation Without Switches Accurate Power Limiting Fixed-Frequency Average Current-Mode Control High Bandwidth (5 MHz), Low-Offset Current Amplifier Integrated Current- and Voltage-Amplifier Output Clamps Multiplier Improvements: Linearity, 500 mV VAC Offset (Eliminates External Resistor), 0 V to 5 V Multout Common-Mode Range VREF GOOD Comparator Faster and Improved Accuracy ENABLE Comparator UVLO Options (16 V/10 V or 10.5 V/10 V) 300-uA Start-Up Supply Current

DESCRIPTION
The UC3854A/B products are pin compatible enhanced versions of the UC3854. Like the UC3854, these products provide all of the functions necessary for active power factor corrected preregulators. The controller achieves near unity power factor by shaping the ac input line current waveform to correspond to the ac input line voltage. To do this the UC3854A/B uses average current mode control. Average current mode control maintains stable, low distortion sinusoidal line current without the need for slope compensation, unlike peak current mode control. A 1%, 7.5-V reference, fixed frequency oscillator, PWM, voltage amplifierwith soft-start, line voltage feedforward (VRMS squarer), input supply voltage clamp, and over current comparator round out the lilst of feataures. Available in the 16-pin N (PDIP), DW (SOIC Wide), and J (CDIP) and 20-pin Q (PLCC) package. See Ordering Information table for availability by temperature range.

BLOCK DIAGRAM
VAO 7 VCC (A) 16 V / 10 V (B) 10.5 V / 10 V ENA 10 2.65 V / 2.15 V 3V VSENSE 11 IAC VRMS 6 8 14 uA SS 13 I MOUT + A C B X2 A B C RUN OSC 20 V 1 GND R R S MOUT 5 CAO PKLMT 3 2 REF 9 7.5 V REF RUN IC POWER 7.1 V 15 VCC

16 GTDRV

4 ISENSE

14 CT

12 RSET

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.