UC1965

UC2965

UC3965

SLUS300A - APRIL 1999

FEATURES

• Accessible 2.5V Precision Reference

• 0.4% Initial Reference Accuracy

• 1% Reference Accuracy over Line,

Load, and Full Temperature Range

• Low 1mV Offset Error Amplifier

• Supports Closed Loop Soft Start

• 2X Inverting Amplifier / Buffer Output

• 4.1V Undervoltage Lockout

• ICC 2mA at 5V

• 8-Pin SOIC or DIL Package

Precision Reference with Low Offset Error Amplifier

8COMP

GND

VOUT

7VFB

6VREF

5NI

1

2

3

4

VCC

OFFSET

EA

OB

UVLO

VREF

2.5V

VCC

15k

+

–

7.5k

5k

+

–

5k

2k

BLOCK DIAGRAM

UDG-98055

DESCRIPTION

The UC3965 is suitable for applications needing greater precision and

more functionality than the TL431 type shunt regulators. The wide range

VCC input capability enables the device to be biased from the secondary

side output voltage rail, resulting in closed loop soft start.

The UC3965 includes an accessible 2.5V precision reference which offers

0.4% initial and 1% reference accuracy over line, load, and full tempera-

ture range with a low offset error amplifier, a 2X inverting amplifier/buffer,

and an undervoltage lockout circuit. The IC is ideally suited for applica-

tions where high precision PWM power supply regulation is required.

Typically, the error amplifier is configured to compare a fraction of the to

be regulated power supply voltage to the on-chip 2.5V reference. The 2X

amplifier/buffer output is then used to drive a PWM controller or regulator.

The UC3965 is also capable of driving an optocoupler diode for isolated

applications.

application

INFO

available