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 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. The device is available in TO-92, TO-243AA (SOT-89), and TO-252 (D-PAK) packages. Applications ❏ ❏ ❏ ❏ ❏ ❏ Off-line SMPS startup circuits Adjustable high voltage constant current source Industrial Controls Motor controls Battery chargers Power supplies LR8 Block Diagram and Typical Application * VOUT R1 C2 RLOAD R2 VIN VIN VOUT ADJ LR8 C1 *Required for conditions where VIN is less than VOUT. 12/03/01 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. 1 LR8 Ordering Information Package Options TO-92 LR8N3 * Product marking for TO-243AA: TO-252 LR8K4 LR8❋ where ❋ = 2-week alpha date code TO-243AA* LR8N8 Same as SOT-89. Product supplied on 2000 piece carrier tape reels. Absolute Maximum Ratings VIN Input Voltage Output Voltage Range Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range *Voltages referenced to ADJ. Pin Configurations 2 (TAB) 1 2 3 -0.5V to +480V* -0.5V to +470V -40°C to +85°C -40°C to +125°C -65°C to +150°C TAB 1 3 123 TO-243AA (SOT-89) VIN TO-92 TO-243AA TO-252 1 1 1 TO-92 VOUT 2 2, TAB 2 (TAB) TO-252 (D-PAK) ADJ 3 3 3 Electrical Characteristics Test conditions unless otherwise specified: -40°C < TA < 85°C. Symbol VIN - VOUT VOUT VOUT ∆VOUT ∆VOUT ∆VOUT IOUT IOUT IOUT IADJ C2 Parameter Input to Output Voltage Difference Overall Output Voltage Regulation Overall Output Voltage Regulation Line Regulation Load Regulation Temperature Regulation Output Current Limit Output Current Limit Minimum Output Current Adjust Output Current Minimum Output Load Capacitance 5 1 50 125 60 0.3 10 -1 10 Min 12 1.14 375 1.20 400 0.003 1.4 Typ Max 450 1.26 425 0.01 3.0 +1 20 0.5 0.5 15 Units V V V %/V % % mA mA mA µA µF dB °C 120Hz, VOUT = 5V 12V