LR645

Features:

` Accepts inputs from 15V to 450V
` Compatible with industry standard PWM ICs. See application note AN-H28.
` Output currents up to 3mA continuous, 30mA peak
` Supply current typically 50A
` 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


Application

· Off-line SMPS startup circuits (pulse loads)
· Low power off-line regulators
· Regulators for noisy inputs


Specifications

Input Voltage                                                               450V
Output Voltage                                                            15.5V
Operating and Storage Temperature         55 to +150
Soldering Temperature*                                              300
*Distance of 1.6mm from case for 10 seconds


Description

The Supertex LR645 is a high input voltage, low output current linear regulator. It has a 3-terminal fixed output voltage version available in TO-92, TO-220 and SOT-89 packages as well as an adjustable voltage version available in 8 pin 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 start-up 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 flows after start-up thereby reducing the continuous power dissipation to a few milliwatts.

The adjustable voltage version allows trimming of the output voltage from 8V to 12V. This version can also be connected to an external depletion mode MOSFET for increased output current.

When used in conjunction with Supertex depletion mode MOSFET DN2540N5, up to a 150mA is achieved.