FEATURES

• Complete 8-pin Power Factor

Solution

• Reduced External Components

• RMS Line Voltage Compensation

• Precision Multiplier/Squarer/Divider

• Internal 63kHz Synchronizable

Oscillator

• Average Current Mode PWM

Control

• Overvoltage Protection Comparator

• High Current, Clamped Gate Driver

DESCRIPTION

The UC2853A provides simple, yet high performance active power factor

correction. Using the same control technique as the UC1854, this 8-pin device

exploits a simplified architecture and an internal oscillator to minimize

external component count. The UC2853A incorporates a precision multiplier/

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 constant

loop gain with changes in input voltage, which minimizes input line

current distortion over the worldwide input voltage range.

The internal 63kHz oscillator includes an external clock input, allowing synchronization

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.

The UC2853A is identical to the UC2853 except the internal oscillator frequency

has been reduced from 75kHz to 63kHz. The switching frequency

is lowered in order to keep the second harmonic of the switching frequency

below a 150kHz. For EMI specifications at 150kHz this makes it easier for

a design to meet system requirements.

These devices are available in 8-pin PDIP (P) and SOIC (D) packages. The

UC2853A is specified for operation from –40°C to 105°C.