LR8

LR8 LR8 High Input Voltage Adjustable 3-Terminal Linear Regulator Features ❏ ❏ ❏ ❏ ❏ ❏ 12V to 450V input voltage range Adjustable 1.20V to 440V output regulation 5% output voltage tolerance Output current limiting 10µA typical ADJ current Internal junction temperature limiting General Description The Supertex LR8 is a high voltage, low output current, adjustable linear regulator. It has a wide operating input voltage range of 12V to 450V. The output voltage can be adjusted from 1.20V to 440V provided that the input voltage is at least 10V 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 amplified by the external resistor ratio R1 and R2. An internal constant bias current of typically 10µA is connected to the ADJ pin. This increases VOUT by a constant voltage of 10µA times R2. The LR8 has current limiting and temperature limiting. The output current limit is typically 15mA and the minimum temperature limit is 125°C. An output short circuit current will therefore be limited to 15mA. 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 ...