LMF380C1J NSC [National Semiconductor], LMF380C1J Datasheet

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LMF380C1J

Manufacturer Part Number
LMF380C1J
Description
LMF380 Triple One-Third Octave Switched-Capacitor Active Filter
Manufacturer
NSC [National Semiconductor]
Datasheet
C 1995 National Semiconductor Corporation
LMF380 Triple One-Third Octave
Switched-Capacitor Active Filter
General Description
The LMF380 is a triple one-third octave filter set designed
for use in audio audiological and acoustical test and mea-
surement applications Built using advanced switched-ca-
pacitor techniques the LMF380 contains three filters each
having a bandwidth equal to one-third of an octave in fre-
quency By combining several LMF380s each covering a
frequency range of one octave a filter set can be imple-
mented that encompasses the entire audio frequency range
while using only a small fraction of the number of compo-
nents and circuit board area that would be required if a con-
ventional active filter approach were used The center fre-
quency range is not limited to the audio band however
Center frequencies as low as 0 125 Hz or as high as 25 kHz
are attainable with the LMF380
The center frequency of each filter is determined by the
clock frequency The clock signal can be supplied by an
external source or it can be generated by the internal oscil-
lator using an external crystal and two capacitors Since the
LMF380 has an internal clock frequency divider (
an output pin for the half-frequency clock signal a single
clock oscillator for the top-octave LMF380 becomes the
master clock for the entire array of filters in a multiple
LMF380 application
Simplified Block Diagram
TL H 11123
d
2) and
Accuracy is enhanced by close matching of the internal
components the ratio of the clock frequency to the center
frequency is typically accurate to
gain and stopband attenuation are guaranteed over the full
temperature range
Features
Y
Y
Y
Key Specifications
Y
Y
Applications
Y
Y
Y
Three bandpass filters with one-third octave center fre-
quency spacing
Choice of internal or external clock
No external components other than clock or crystal and
two capacitors
Passband gain accuracy Better than 0 7 dB over
temperature
Supply voltage range
Real-Time Audio Analyzers (ANSI Type E Class II)
Acoustical Instrumentation
Noise Testing
g
2V to
TL H 11123 – 1
g
g
7 5V or
0 5% and passband
RRD-B30M115 Printed in U S A
November 1995
a
4V to
a
14V

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LMF380C1J Summary of contents

Page 1

LMF380 Triple One-Third Octave Switched-Capacitor Active Filter General Description The LMF380 is a triple one-third octave filter set designed for use in audio audiological and acoustical test and mea- surement applications Built using advanced switched-ca- pacitor techniques the LMF380 contains ...

Page 2

Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Total Supply Voltage Voltage at Any Pin Input Current per Pin ...

Page 3

Logic Input and Output Electrical Characteristics The following specifications for and all other limits apply for MAX A J Symbol Parameter V XTAL1 Logical ‘‘1’’ CMOS ...

Page 4

Typical Performance Characteristics Power Supply Current vs Power Supply Voltage Negative Output Swing vs Load Resistance Offset Voltage vs Supply Voltage Power Supply Current Positive Output Swing vs Temperature vs Load Resistance Positive Output Swing Negative Output Swing vs Temperature ...

Page 5

Connection Diagrams Dual-In-Line Package Top View Order Number LMF380CIJ LMF380CMJ or LMF380CIN See NS Package Number J16A or N16E Plastic Chip Carrier Package Top View Order Number LMF380CIV See NS Package Number V20A Pin Description GND This is the analog ...

Page 6

Applications Information POWER SUPPLIES The LMF380 can operate from a total supply voltage ( ranging from 14V but the choice of supply voltage can affect circuit performance The IC depends on MOS switches ...

Page 7

Typical Applications FIGURE 3 Complete one-third octave filter set for the entire audio frequency range Ten LMF380s provide the thirty bandpass filters required for this function Power supply connections and bypass capacitors are not shown Pin numbers are for the ...

Page 8

Typical Applications (Continued) THIRD-OCTAVE ANALYZER FILTER SET The circuit shown in Figure 3 uses the LMF380 to imple- ment a -octave filter set for use in ‘‘real time’’ audio pro- gram analyzers Ten LMF380s provide all of the bandpass filtering ...

Page 9

Typical Applications (Continued) (a) FIGURE 4 Examples of detectors for audio signals (a) Half-wave peak detector (b) Half-wave average detector (c) Full-wave peak detector (d) Full-wave average detector All diodes are 1N914 or 1N4148 Input RC low-pass filters attenuate clock ...

Page 10

Typical Applications (Continued) FIGURE 5 LED display using LM3915 bar graph driver The input voltage range is 2V full-scale with 3 dB per step TL H 11123– ...

Page 11

... Physical Dimensions inches (millimeters) Order Number LMF380C1J or LMF380CMJ Dual-In-Line Package (J) NS Package Number J16A Dual-In-Line Package (N) Order Number LMF380CIN NS Package Number N16E 11 ...

Page 12

Physical Dimensions inches (millimeters) (Continued) LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 ...

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