CORPORATION

1/9

ISSUED DATE :2004/04/19

REVISED DATE :2004/09/30B

G

H

S

Description

The GP3843 is specifically designed for Off-Line and dc-to-dc converter applications offering the designer a cost-effective solution with

minimal external components.

The GP3843 has UVLO thresholds 8.5V(on) and 7.6V(off),ideally suited for off-line converters.

Features

*Trimmed Oscillator for Precise Frequency Control

*Oscillator Frequency Guaranteed at 250kHz

*Current Mode Operation to 500kHz

*Automatic Feed Forward Compensation

*latching PWM for Cycle-By-Cycle Current Limiting

*Internally Trimmed Reference with Undervoltage Lockout

*High Current Totem Pole Output

*Undervoltage Lockout with Hysteresis

*Low Startup and Operating Current

Package Dimensions

Millimeter

Millimeter

REF.

Min.

Max.

REF.

Min.

Max.

A

-

0.5334

c1

0.203

0.279

A1

0.381

-

D

9.017

10.16

A2

2.921

4.953

E

6.096

7.112

b

0.356

0.559

E1

7.620

8.255

b1

0.356

0.508

e

2.540 BSC

b2

1.143

1.778

HE

-

10.92

b3

0.762

1.143

L

2.921

3.810

c

0.203

0.356

DIP-8L

Function

Description

Pin1:Compensation

This pin is the Error Amplifier output and is made available for loop

compensation.

Pin2:Voltage Feedback

This is the inverting input of the Error Amplifier. It’s normally connected to the

Switching power supply output through a resistor divider.

Pin3:Current Sense

A voltage proportional to inductor current is connected to this input .The

PWM uses this information to terminate the output switch conduction.

Pin4:RT/CT

The oscillator frequency and maximum output duty cycle are programmed by

connecting resistor RT to Vref and capacitor CT to ground .Operation 500kHz

is possible.

Pin5:Ground

This pin is the combined control circuitry and power ground.

Pin6:Output

This output directly drives the gate of a power MOSFET. Peak currents up to

1 A are sourced and sunk by this pin.

Pin7:Vcc

This pin is the positive supply of the control IC.

Pin8:Vref

This is the reference output .It provides charging current for capacitor CT

through resistor RT.

Absolute Maximum Ratings at Ta = 25 ::::

Parameter

Symbol

VALUE

Unit

Total power Supply and Zener current

(ICC+Iz)

30

mA

Output current, source or sink(note1)

Io

1.0

A

Output energy(capacitive load per cycle)

W

5.0

J

Current sense and voltage feedback inputs

Vin

-0.3 to 5.5

V

SEATING PLANE

e

b

Z

Z

D

SECTION Z - Z

b

GAUGE PLANE

DIP-8