General Description

The Supertex LR645 is a high input voltage, low output current linear regulator. It has a 3-terminal fi xed output voltage version available in TO-92, TO-220 and SOT-89 packages, as well as an adjustable voltage version available in an 8- lead SOIC package. The 3-terminal version functions like any other low voltage 3-terminal regulator except it allows the use of much higher input voltages. When used in a SMPS startup circuit, it eliminates the need for large power resistors. In this application, current is drawn from the high voltage line only during start-up. Only leakage current fl ows after start-up, thereby reducing the continuous power dissipation to a few milliwatts.

Features

► Accepts inputs from 15V to 450V

► Output currents up to 3.0mA continuous, 30mA peak

► Supply current typically 50µA

► Line regulation typically 0.1mV/V

► Output can be trimmed from 8.0V to 12V

► Output current can be increased to 150mA with external FET

Applications

► Off-line SMPS startup circuits (pulse loads)

► Low power off-line regulators

► Regulators for noisy inputs