The LM3411 is a low-power fixed-voltage (3.3 V or
5 V) precision shunt regulator designed specifically for driving an optoisolator to provide
feedback isolation in a switching regulator.
The LM3411 circuitry includes an internally compensated operational amplifier, a bandgap
reference, NPN output transistor, and voltage setting resistors.
A trimmed precision bandgap reference with temperature drift curvature correction
provides a ensured 1% precision over the operating temperature range (A grade version). The
inverting input of the amplifier is externally accessible for loop frequency compensation when used
as part of a larger servo system. The output is an open-emitter NPN transistor capable of driving
up to 15 mA of load current.
Because of its small die size, the LM3411 has been made available in the subminiature
5-pin SOT-23 surface-mount package. This package is ideal for use in space-critical
Although its main application is to provide a precision output voltage (no trimming
required) and maintain very good regulation in isolated DC-DC converters, it can also be used with
other types of voltage regulators or power semiconductors to provide a precision output voltage
without precision resistors or trimming.
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