UC1854A

*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
V _ACOffset (Eliminates External Resistor), 0 V
to 5 V Multout Common-Mode Range
*V _REF GOOD Comparator REF
*Faster and Improved Accuracy ENABLE
Comparator
*UVLO Options  (16 V/10 V or 10.5 V/10 V)
*300-A Start-Up Supply Current

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  disto -rtion 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 amplifier with soft-start, line voltage feedforward (V_RMS  squarer), input supply voltage clamp, and over current comparator round out the list of features.
Available in the 16-pin N (PDIP), DW (SOICWide), and J (CDIP) and 20-pin Q (PLCC) package. See ordering infor -mation on page 3 for availability by temperature range.