Electronic Design

Off-Line Linear Regulator Offers Adjustable Output Voltages

Designed for off-line power-supply applications, the LR8 three-terminal 450-V linear regulator has adjustable output voltages. This high-voltage, low-output current regulator suits telecom power supplies that encounter wide input-voltage variations and high-voltage line transients.

The LR8's input voltage ranges from 12 to 450 V. Using two external resistors, its output voltage can be adjusted from 1.20 to 440 V when the input voltage is at least 10 V greater than the output. While the load regulation is ±3% for an output load of 0.5 to 10 mA, its maximum line regulation is 0.01%/V for any input line voltage between 15 to 400 V and a 5.0-V output. Maximum guaranteed output current is 10 mA.

Also, the LR8 features current limiting and thermal shutdown. The output current limit is 15 mA. Its minimum junction temperature limit is 125°C. It comes in 3-pin SOT-89 (LR8N8) and TO-92 (LR8N3) packages. In 1000-unit quantities, the LR8N8 costs $0.54, and the LR8N3 costs $0.52.

Supertex Inc., 1235 Bordeaux Dr., Sunnyvale, CA 94089; (408) 744-0100; www.supertex.com.

See associated figure.

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