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FEATURES
Complete 8-pin Power Factor
Solution
Reduced External Components
RMS Line Voltage Compensation
Precision Multiplier/Squarer/Divider
Internal 75kHz Synchronizable
Oscillator
Average Current Mode PWM
Control
Overvoltage Protection Comparator
High Current, Clamped Gate Driver
DESCRIPTION
The UC3853 provides simple, yet high performance active power factor
correction. Using the same control technique as the UC1854, this 8-pin de-
vice exploits a simplified architecture and an internal oscillator to minimize
external component count. The UC3853 incorporates a precision multi-
plier/squarer/divider circuit, voltage and current loop error amplifiers, and a
precision voltage reference to implement average current mode control
with RMS line voltage compensation. This control technique maintains con-
stant loop gain with changes in input voltage, which minimizes input line
current distortion over the worldwide input voltage range.
The internal 75kHz oscillator includes an external clock input, allowing syn-
chronization to downstream converters. Additionally, the device features an
overvoltage protection comparator, a clamped MOSFET gate driver which
self-biases low during undervoltage lockout, and low startup and supply
current.
These devices are available in 8-pin plastic and ceramic dual in-line (DIP)
packages, and 8-lead small outline (SOIC) packages. The UC1853 is
specified for operation from 鈥?5掳C to +125掳C, the UC2853 is specified for
operation from 鈥?5掳C to +85掳C, and the UC3853 is specified for operation
from 0掳C to +70掳C.
BLOCK DIAGRAM
UDG-94120-1
11/97
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