MC33260

http://onsemi.com

8

PIN FUNCTION DESCRIPTION

Pin No.

Function

Description

1

Feedback Input

This pin is designed to receive a current that is proportional to the preconverter output voltage. This

information is used for both the regulation and the overvoltage and undervoltage protections. The

current drawn by this pin is internally squared to be used as oscillator capacitor charge current.

2

Vcontrol

This pin makes available the regulation block output. The capacitor connected between this pin and

ground, adjusts the control bandwidth. It is typically set below 20 Hz to obtain a nondistorted input

current.

3

Oscillator Capacitor

(CT)

The circuit uses an on–time control mode. This on–time is controlled by comparing the CT voltage to

the Vcontrol voltage. CT is charged by the squared feedback current.

4

Zero Current

Detection Input

This pin is designed to receive a negative voltage signal proportional to the current flowing through

the inductor. This information is generally built using a sense resistor. The Zero Current Detection

prevents any restart as long as the pin 4 voltage is below (–60 mV). This pin is also used to perform

the peak current limitation. The overcurrent threshold is programmed by the resistor connected

between the pin and the external current sense resistor.

5

Synchronization

Input

This pin is designed to receive a synchronization signal. For instance, it enables to synchronize the

PFC preconverter to the associated SMPS. If not used, this pin must be grounded.

6

Ground

This pin must be connected to the preregulator ground.

7

Gate Drive

The gate drive current capability is suited to drive an IGBT or a power MOSFET.

8

VCC

This pin is the positive supply of the IC. The circuit turns on when VCC becomes higher than 11 V, the

operating range after start–up being 8.5 V up to 16 V.

APPLICATION SCHEMATIC

18

7

6

5

2

3

4

L1

Filtering

Capacitor

Sync

M1

C1

D1

+

Vcontrol

VCC

Load

(SMPS, Lamp

Ballast,...)

Ro

CT

ROCP

Rcs

D1...D4