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DS20005399A-page 1

LR8

Features

• 13.2 - 450V input voltage range

• Adjustable 1.20 - 438V output regulation

• 5% output voltage tolerance

• Output current limiting

• 10µA typical ADJ current

• Internal junction temperature limiting

Applications

• Off-line SMPS startup circuits

• Adjustable high voltage constant current source

• Industrial controls

• Motor controls

• Battery chargers

• Power supplies

Description

LR8 is a high-voltage, low-output current, adjustable

linear regulator. This regulator has a wide operating

input voltage range of 13.2 - 450V. The output voltage

can be adjusted from 1.20 - 438V, provided that the

input voltage is at least 12V greater than the output

voltage. The output voltage can be adjusted by means

typical application circuits. LR8 regulates the voltage

difference between VOUT and ADJ pins to a nominal

value of 1.20V. The 1.20V is amplified by the external

rent, of typically 10µA, is connected to the ADJ pin.

times R2.

LR8 provides both current and temperature limiting.

The output current limit is typically 20mA and the mini-

mum temperature limit is 125°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

prevent the junction temperature from exceeding its

temperature limit. For SMPS start-up circuit applica-

tions, 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

1.0µF or larger and a minimum DC output current of

500µA are required.

LR8 is available in TO-243AA (SOT-89), TO-252 (D-

PAK), and TO-92 packages.

High-Input Voltage, Adjustable, 3-Terminal,

Linear Regulator