LR8_07 Datasheet, PDF(1/9 Page) Supertex, Inc – High Input Voltage Adjustable 3-Terminal Linear Regulator

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LR8_07 Datasheet, PDF (1/9 Pages) Supertex, Inc – High Input Voltage Adjustable 3-Terminal Linear Regulator

LR8

High Input Voltage

Adjustable 3-Terminal Linear Regulator

Features

âº 13.2V to 450V input voltage range

âº Adjustable 1.20V to 440V output regulation

âº 5% output voltage tolerance

âº Output current limiting

âº 10ÂµA typical ADJ current

âº Internal junction temperature limiting

Applications

âº Off-line SMPS startup circuits

âº Adjustable high voltage constant current source

âº Industrial controls

âº Motor controls

âº Battery chargers

âº Power supplies

General Description

The Supertex LR8 is a high voltage, low output current,

adjustable linear regulator. It has a wide operating input

voltage range of 13.2V to 450V. The output voltage can be

adjusted from 1.20V to 440V provided that the input voltage

is at least 12V greater than the output voltage. The output

voltage can be adjusted by means of two external resistors

R1 and R2 as shown in the typical application circuits. The

LR8 regulates the voltage difference between VOUT and ADJ

pins to a nominal value of 1.20V. The 1.20V is ampliï¬ed by

the external resistor ratio R1 and R2. An internal constant bias

current of typically 10ÂµA is connected to the ADJ pin. This

increases VOUT by a constant voltage of 10ÂµA times R2.

The LR8 has current limiting and temperature limiting. The

output current limit is typically 20mA and the minimum

temperature limit is 125Â°C. An output short circuit current will

therefore be limited to 20mA. When the junction temperature

reaches its temperature limit, the output current and/or output

voltage will decrease to keep the junction temperature from

exceeding its temperature limit. For SMPS start-up circuit

applications, the LR8 turns off when an external voltage

greater than the output voltage of the LR8 is applied to VOUT

of the LR8. To maintain stability, a bypass capacitor of 1.0ÂµF

or larger and a minimum DC output current of 500ÂµA are

required.

The device is available in TO-243AA (SOT-89), TO-252 (D-

PAK), and TO-92 packages.

Typical Application Circuit

VOUT

VIN

VIN VOUT

ADJ

LR8

RLOAD

*Required for conditions where VIN is less than VOUT.

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