Datasheet LR8 (Microchip)

LR8
High-Input Voltage, Adjustable, 3-Terminal,
Linear Regulator
Features General Description •
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• 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 of two
external resistors, R1 and R2, as shown in the 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 resistor
ratio R1 and R2. An internal constant bias current, of
typically 10 µA, is connected to the ADJ pin. This
increases VOUT by a constant voltage of 10 µA times
R2. 13.2-450V Input Voltage Range
Adjustable 1.20-438V Output Regulation
5% Output Voltage Tolerance
Output Current Limiting
10 µA Typical ADJ Current
Internal Junction Temperature Limiting Applications
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• Offline SMPS startup circuits
Adjustable high-voltage constant current source
Industrial controls
Motor controls
Battery chargers
Power supplies LR8 provides both current and temperature limiting.
The output current limit is typically 20 mA and the
minimum temperature limit is +125°C. An output shortcircuit 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 applications, 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
1.0 µF or larger and a minimum DC output current of
500 µA are required.
LR8 is available in TO-243AA (SOT-89), TO-252 (DPAK) and TO-92 packages.  2015-2017 Microchip Technology Inc. DS20005399B-page 1