NCP1217, NCP1217A

http://onsemi.com

2

Figure 1. Typical Application Example

EMI

FILTER

UNIVERSAL

INPUT

+

+

NCP1217

+

Aux.

Adj

FB

CS

Gnd

HV

Drv

1

2

3

4

8

7

6

5

Ramp Adjustment

See Application

Section

PIN FUNCTION DESCRIPTION

Pin No.

Pin Name

Function

Description

1

Adj

Adjust the skipping peak current

This pin lets you adjust the level at which the cycle skipping process takes

place. Shorting this pin to ground permanently disables the skip cycle

feature.

By bringing this pin above 3.1 V, you permanently shut off the device.

2

FB

Sets the peak current setpoint

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

justed accordingly to the output power demand.

3

CS

Current sense input

This pin senses the primary current and routes it to the internal compara-

tor via an L.E.B. By inserting a resistor in series with the pin, you control

the amount of ramp compensation you need.

4

Gnd

The IC ground

−

5

Drv

Driving pulses

The driver’s output to an external MOSFET.

6

Supplies the IC

This pin is connected to an external bulk capacitor of typically 22

mF.

7

NC

−

This unconnected pin ensures adequate creepage distance.

8

HV

Ensures a clean and lossless

startup sequence

Connected to the high−voltage rail, this pin injects a constant current into