Features

• Accepts Inputs from 15 to 450V

• Output Currents: Up to 3.0 mA Continuous,

30 mA Peak

• Supply Current Typically 50 μA

• Line Regulation Typically 0.1 mV/V

• Output Can Be Trimmed from 8.0 to 12V

• Output Current Can be Increased to 150 mA with

External FET

Applications

• Off-line SMPS Startup Circuits (Pulse Loads)

• Low Power Off-Line Regulators

• Regulators for Noisy Inputs

Description

LR645 is a high-input voltage, low-output current, linear

regulator that is available in two versions. A 3-terminal,

fixed-output voltage version is 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 of LR645 functions like any

other low-voltage, 3-terminal regulator except it allows

the use of much higher-input voltages. When used in a

Switched-mode Power Supply (SMPS), start-up circuit,

LR645 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 8.0V to 12V. This version can also

be connected to an external depletion mode

metal-oxide-semiconductor field-effect transistor

(MOSFET) for increased output current. When used in

conjunction with depletion mode MOSFET DN2540N5,

an output current of up to 150 mA is achieved.