1

LR645

General Description

The Supertex LR6 is a high input voltage, low output current

linear regulator. It has a 3-terminal fixed output voltage version

available in TO-92, TO-220 and SOT-89 packages as well as an

adjustable voltage version available in 8 pin SOIC package. The

3-terminal version functions like any other low voltage 3-terminal

regulator except it allows the use of much higher input voltages.

When used in a SMPS start-up circuit, it eliminates the need for

large power resistors. In this application, current is drawn from

the high voltage line only during start-up. Only leakage current

flows after start-up thereby reducing the continuous power

dissipation to a few milliwatts.

The adjustable voltage version allows trimming of the output

voltage from 8V to 12V.This version can also be connected to an

external depletion mode MOSFET for increased output current.

When used in conjunction with Supertex depletion mode MOSFET

DN2540N5, up to a 150mA is achieved.

Max. Input Voltage

TO-92

TO-243AA*

TO-220

SO-8

Die

450V

LR645N3

LR645N8

LR645N5

LR645LG LR645ND

*Same as SOT-89. Product supplied on 2000 piece carrier tape reels.

Ordering Information

Features

❏ Accepts inputs from 15V to 450V

❏ Compatible with industry standard PWM ICs.

See application note AN-H28.

❏ Output currents up to 3mA continuous, 30mA peak

❏ Supply current typically 50µA

❏ Line regulation typically 0.1mV/V

❏ Output can be trimmed from 8.0V to 12V

❏ Output current can be increased to 150mA with external FET

High Input Voltage

SMPS Start-up / Linear Regulator

(continued on page 14-3)

Absolute Maximum Ratings

Input Voltage

450V

Output Voltage

15.5V

Operating and Storage Temperature

–55

°C to +150°C

Soldering Temperature*

300

°C

*Distance of 1.6mm from case for 10 seconds

Applications

❏ Off-line SMPS startup circuits (pulse loads)

❏ Low power off-line regulators

❏ Regulators for noisy inputs

Pin Configuration

+V

IN

GND

V

OUT

Trim

Gate

TO-92

1

2

3

—

—

TO-243AA

1

2, TAB

3

—

—

TO-220

1

2, TAB

3

—

—

P-DIP

13457

SO-8

5

4

3

2

1

TO-243AA

(SOT-89)

3

2

1

TAB

1 2 3

TO-92

1

2 3

TO-220

TAB

Caution

The LR6 does NOT provide galvanic isolation. When

operated from an AC line, potentially lethal voltages can be

present on the IC. Adequate means of protecting the end

user from such voltages must be provided by the circuit

developer.

For detailed circuit and application information, please refer

to application note AN-H28.

Order Number / Package

Product marking for TO-243AA:

LR6

❋

where

❋ = 2-week alpha date code

11/12/01

Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability

indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to

workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the

Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.