LM3411 Datasheet, PDF (1/13 Pages) National Semiconductor (TI) – Precision Secondary Regulator/Driver

December 1999
LM3411
Precision Secondary Regulator/Driver
General Description
The LM3411 is a low power fixed-voltage (3.3V or 5.0V) pre-
cision shunt regulator designed specifically for driving an op-
toisolator to provide feedback isolation in a switching regula-
tor.
The LM3411 circuitry includes an internally compensated op
amp, a bandgap reference, NPN output transistor, and volt-
age setting resistors.
A trimmed precision bandgap reference with temperature
drift curvature correction, provides a guaranteed 1% preci-
sion over the operating temperature range (A grade version).
The amplifier’s inverting input 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 sub-miniature 5-lead SOT23-5 surface
mount package. This package is ideal for use in space criti-
cal applications.
Although its main application is to provide a precision output
voltage (no trimming required) and maintain very good regu-
lation 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.
Features
n Fixed voltages of 3.3V and 5.0V with initial tolerance of
±1% for standard grade and ±0.5% for A grade
n Custom voltages available (3V–17V)
n Wide output current range, 20 µA–15 mA
n Low temperature coefficient
n Available in 5-lead SOT23-5 surface mount package
(tape and reel)
Applications
n Secondary controller for isolated DC/DC PWM switching
regulators systems
n Use with LDO regulator for high-precision fixed output
regulators
n Precision monitoring applications
n Use with many types of regulators to increase precision
and improve performance
Typical Application and Functional Diagram
Basic Isolated DC/DC Converter
DS011987-1
DS011987-2
LM3411 Functional Diagram
SIMPLE SWITCHER™ is a tradmark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS011987
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