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.