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NCP1028

High−Voltage Switcher for Medium Power Offline SMPS Featuring Low Standby Power

ON Semiconductor 

NCP1028

85−265 VAC

+

BO

+

OPP*

NCP1028

1

8

2

7

3

+4

5

*Optional component

Ramp

Comp.*

Figure 1. Typical Application

Vout

+

GND

PIN FUNCTION DESCRIPTION

Pin No.

Symbol

Function

1

VCC

Powers the Internal

Circuitry

2

Ramp Comp.

Ramp Compensation

in CCM

3

Brown−Out

Brown−Out and

Latchoff Input

4

FB

Feedback Signal Input

5

Drain

Drain Connection

−

−

−

7

OPP

Over Power Protection

8

GND

The IC Ground

Description

This pin is connected to an external capacitor of typically 22 mF.

To extend the duty cycle operation in Continuous Conduction Mode (CCM),

pin 3 offers the ability to inject ramp compensation in the controller. If unused,

short this pin to VCC.

By monitoring the bulk level via a resistive network, the circuit protects itself

from low mains conditions. If an external event brings this pin above 4.0 V,

the part fully latches off.

By connecting an optocoupler to this pin, the peak current setpoint is adjusted

accordingly to the output power demand.

The internal drain power switch circuit connection.

This unconnected pin ensures adequate creepage distance.

Driving this pin reduces the power supply capability in high line conditions. If

no Over Power Protection is needed, short this pin to ground.

−

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2

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