LR8K4-G Microchip

LR8 High-Input Voltage, Adjustable, 3-Terminal, Linear Regulator Features General Description 13.2-450V Input Voltage Range LR8 is a high-voltage, low-output current, adjustable Adjustable 1.20-438V Output Regulation linear regulator. This regulator has a wide operating 5% Output Voltage Tolerance input voltage range of 13.2-450V. The output voltage can be adjusted from 1.20-438V, provided that the input Output Current Limiting voltage is at least 12V greater than the output voltage. 10 A Typical ADJ Current The output voltage can be adjusted by means of two Internal Junction Temperature Limiting external resistors, R and R , as shown in the typical 1 2 application circuits. LR8 regulates the voltage differ- Applications ence between V and ADJ pins to a nominal value of OUT 1.20V. The 1.20V is amplified by the external resistor Offline SMPS startup circuits ratio R and R . An internal constant bias current, of 1 2 Adjustable high-voltage constant current source typically 10A, is connected to the ADJ pin. This Industrial controls increases V by a constant voltage of 10 A times OUT Motor controls R . 2 Battery chargers LR8 provides both current and temperature limiting. Power supplies The output current limit is typically 20 mA and the minimum temperature limit is +125C. An output short- circuit current will therefore be limited to 20 mA. 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 V of OUT the LR8. To maintain stability, a bypass capacitor of 1.0 F or larger and a minimum DC output current of 500 A are required. LR8 is available in TO-243AA (SOT-89), TO-252 (D- PAK) and TO-92 packages. 2015-2017 Microchip Technology Inc. DS20005399B-page 1LR8 Package Type VOUT ADJ ADJ 9 ,1 V OUT V IN 9 287 TO-243AA (SOT-89) TO-92 V OUT ADJ V IN TO-252 See Table 2-1 for pin information Functional Block Diagram Pass V V IN OUT Element Overtemp & Overcurrent 1.2V 10 A ADJ LR8 DS20005399B-page 2 2015-2017 Microchip Technology Inc.