Primary Side PWM Controller

AS2208

79

ASTEC Semiconductor

Pin Function Description

Pin Number

Function

Description

1

COMP

This is the inverting input to the PWM comparator. A divided and level shifted

representation of this voltage is compared to the ISNS input to determine OUT duty

cycle. A 1 mA current source is provided as a pull-up for an optocoupler.

2

ISNS

A voltage proportional to inductor current is connected to this pin. The PWM uses this

information to terminate the gate drive of the output.

3

RT/CT

4

OV

This pin latches OUT low when pulled above 2.5 V. The latch can be reset by pulling

OV above 4 V then back to ground.

5

GND

Circuit common ground.

6

OUT

This totem pole output is designed to directly drive a power MOSFET switch capable of

sourcing and sinking peak currents up to 1 A.

Positive supply voltage for the IC.

Output of 5V series regulator.

Absolute Maximum Ratings

Parameter

Symbol

Rating

Unit

Self-Limiting

V

Supply Voltage (Low Impedance Source)

20

V

Reference Current

200

mA

Output Current

1A

Output Voltage

20

V

Continuous Power Dissipation at 25

500

mW

Junction Temperature

150

°C

Storage Temperature Range

– 65 to 150

°C

Lead Temperature, Soldering 10 Seconds

300

°C

Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress

rating only and functional operation of the device at these or any other conditions above indicated in the operational sections of this

specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.

Recommended Conditions

Parameter

Symbol

Rating

Unit

Supply Voltage

10 - 15

V

Oscillator

50 - 250

kHz

Typical Thermal Resistance

Package

Typical Derating

8L PDIP

95

° C/W

50

° C/W

10.5 mW/

°C

8L SOIC

175

° C/W

45

° C/W

5.7 mW/

°C