NSC LMF380CIN, LMF380CIJ Datasheet
TL/H/11123
LMF380 Triple One-Third Octave Switched-Capacitor Active Filter
November 1995
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 measurement applications. Built using advanced switched-capacitor techniques, the LMF380 contains three filters, each
having a bandwidth equal to one-third of an octave in frequency. By combining several LMF380s, each covering a
frequency range of one octave, a filter set can be implemented that encompasses the entire audio frequency range
while using only a small fraction of the number of components and circuit board area that would be required if a conventional active filter approach were used. The center frequency 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 oscillator, using an external crystal and two capacitors. Since the
LMF380 has an internal clock frequency divider (
d
2) and
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.
Accuracy is enhanced by close matching of the internal
components: the ratio of the clock frequency to the center
frequency is typically accurate to
g
0.5%, and passband
gain and stopband attenuation are guaranteed over the full
temperature range.
Features
Y
Three bandpass filters with one-third octave center frequency spacing
Y
Choice of internal or external clock
Y
No external components other than clock or crystal and
two capacitors
Key Specifications
Y
Passband gain accuracy: Better than 0.7 dB over
temperature
Y
Supply voltage range:g2V tog7.5V ora4V toa14V
Applications
Y
Real-Time Audio Analyzers (ANSI Type E, Class II)
Y
Acoustical Instrumentation
Y
Noise Testing
Simplified Block Diagram
TL/H/11123– 1
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
Absolute Maximum Ratings (Notes1&2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Total Supply Voltage
b
0.3V toa16V
Voltage at Any Pin V
b
b
0.3V to V
a
a
0.3V
Input Current per Pin (Note 3)
g
5mA
Total Input Current (Note 3)
g
20 mA
Lead Temperature (Soldering 10 sec.)
Dual-In-Line Package (Plastic) 300§C
Surface Mount Package (Note 4)
Vapor Phase (60 seconds) 215
§
C
Infrared (15 seconds) 220
§
C
Power Dissipation (Note 5) 500 mW
Maximum Junction Temperature 150
§
C
Storage Temperature Range
b
65§Ctoa150§C
ESD Susceptibility (Note 6) 2000V
Operating Ratings (Note 1)
Temperature Range T
MIN
s
T
A
s
T
MAX
LMF380CIN, LMF380CIV,
LMF380CIJ
b
40§CsT
A
s
a
85§C
LMF380CMJ
b
55§CsT
A
s
a
125§C
Supply Voltage (V
a
b
Vb) 4.0V to 14V
Clock Input Frequency 10 Hz to 1.25 MHz
Filter Electrical Characteristics The following specifications apply for V
a
ea
5V, V
b
eb
5V, and f
CLK
e
320 kHz unless otherwise specified. Boldface limits apply for T
MIN
to T
MAX
; all other limits apply for T
A
e
T
J
e
25§C.
Symbol Parameter Conditions
Typical Limit Units
(Note 7) (Note 8) (Limit)
f
CLK:f01
Clock-to-Center-Frequency Ratio, Filter 1 50:1
f
CLK:f02
Clock-to-Center-Frequency Ratio, Filter 2 62.5:1
f
CLK:f03
Clock-to-Center-Frequency Ratio, Filter 3 80:1
A
1
Gain at f
1
e
3720 Hz (Filter 1), (Note 9)
b
32
b
30 dB (max)
2960 Hz (Filter 2), 2340 Hz (Filter 3)
A
2
Gain at f
2
e
6080 Hz (Filter 1), (Note 9)
a
0.1 0.1g0.7 dB (max)
4820 Hz (Filter 2), 3820 Hz (Filter 3)
A
3
Gain at f
3
e
6200 Hz (Filter 1), (Note 9
0.0
b
0.0g0.7 dB (max)
4960 Hz (Filter 2), 3940 Hz (Filter 3)
A
4
Gain at f
4
e
6400 Hz (Filter 1), (Note 9)
b
0.2
b
0.2
g
0.7 dB (max)
5080 Hz (Filter 2), 4040 Hz (Filter 3)
A
5
Gain at f
5
e
6540 Hz (Filter 1), (Note 9)
b
0.1
b
0.1g0.7 dB (max)
5180 Hz (Filter 2), 4120 Hz (Filter 3)
A
6
Gain at f
6
e
6720 Hz (Filter 1), (Note 9)
a
0.15
b
0.15g0.7 dB (max)
5340 Hz (Filter 2), 4240 Hz (Filter 3)
A
7
Gain at f
7
e
8900 Hz (Filter 1), (Note 9)
b
22
b
20 dB (max)
7060 Hz (Filter 2), 5600 Hz (Filter 3)
V
OS
Output Offset Voltage, Each Filter
a
50
a
120 mV (max)
b
30 mV (min)
En Total Output Noise, OUT1 0.1 Hz to 20 kHz 240
Total Output Noise, OUT2 210 mVrms
Total Output Noise, OUT3 190
C
L
Maximum Capacitive Load 200 pF
Crosstalk V
IN
e
1 Vrms, fef
O
b
67 dB
Clock Feedthrough, Each Filter V
a
ea
5V, V
b
eb
5V 10 mV
p-p
V
OUT
Output Voltage Swing R
L
e
5kX
a
4.2
a
3.8 V (min)
b
4.6
b
4.2 V (max)
THD Total Harmonic Distortion V
IN
e
1 Vrms, fef
O
0.05 %
I
S
Supply Current 6.0 9.0 mA (max)
2
Logic Input and Output Electrical Characteristics
The following specifications for V
a
ea
5V and V
b
eb
5V unless otherwise specified. Boldface limits apply for T
MIN
to
T
MAX
; all other limits apply for T
A
e
T
J
ea
25§C.
Symbol Parameter Conditions
(Note 7)
Typical
Tested
(Limit)
Units
Limit
(Note 8)
V
IH
XTAL1 Logical ‘‘1’’ V
a
e
5V, V
b
eb
5V
a
3.0 V (min)
V
IL
CMOS Clock Logical ‘‘0’’
b
3.0 V (max)
V
IH
Input Voltage
Logical ‘‘1’’ V
a
e
10V, V
b
e
0V
a
8.0 V (min)
V
IL
Logical ‘‘0’’
a
2.0 V (max)
V
IH
Logical ‘‘1’’ V
a
e
2.5V, V
b
eb
2.5V
a
1.5 V (min)
V
IL
Logical ‘‘0’’
b
1.5 V (max)
V
IH
Logical ‘‘1’’ V
a
e
5V, V
b
e
0V
a
4.0 V (min)
V
IL
Logical ‘‘0’’
a
1.0 V (max)
V
OH
Clock Output Logical ‘‘1’’ I
OUT
eb
1mA V
a
b
1.0 V (min)
V
OL
Clock Output Logical ‘‘0’’ I
OUT
ea
1mA V
b
a
1.0 V (max)
I
IN
Input Current XTAL1
g
20 mA (max)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional. These ratings do not guarantee specific performance limits, however. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under
the listed test conditions.
Note 2: All voltages are measured with respect to GND unless otherwise specified.
Note 3: When the input voltage (V
IN
) at any pin exceeds the power supplies (V
IN
k
Vbor V
IN
l
Va), the current at that pin should be limited to 5 mA. The 20 mA
maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four.
Note 4: See AN450 ‘‘Surface Mounting Methods and Their Effect on Product Reliability’’ or the section titled ‘‘Surface Mount’’ found in any volume of the Linear
Data Book Rev. 1 for other methods of soldering surface mount devices.
Note 5: The maximum power dissipation must be derated at elevated temperatures and is a function of T
Jmax
, iJA, and the ambient temperature, TA. The
maximum allowable power dissipation at any temperature is P
D
e
(T
Jmax
b
TA)/iJAor the number given in the Absolute Maximum Ratings, whichever is lower.
For guaranteed operation, T
Jmax
e
125§C. The typical thermal resistance (iJA) of the LMF380N when board-mounted is 51§C.W. iJAis typically 52§C/W for the
LMF380J, and 86
§
C/W for the LMF380V.
Note 6: Human body model, 100 pF discharged through a 1.5 kX resistor.
Note 7: Typicals are at T
J
e
25§C and represent the most likely parametric norm.
Note 8: Limits are guaranteed to National’s Averge Outgoing Quality Level (AOQL).
Note 9: The nominal test frequencies are: f
1
e
0.58 fO,f
2
e
0.95 fO,f
3
e
0.98 fO,f
4
e
fO,f
5
e
1.02 fO,f
6
e
1.05 fO, and f
7
e
1.39 fO. The actual test
frequencies listed in the table may differ slightly from the nominal values.
3
Typical Performance Characteristics
vs Power Supply Voltage
Power Supply Current
vs Temperature
Power Supply Current
vs Load Resistance
Positive Output Swing
vs Load Resistance
Negative Output Swing
vs Temperature
Positive Output Swing
vs Temperature
Negative Output Swing
vs Supply Voltage
Offset Voltage
vs Temperature
Offset Voltage
vs Clock Frequency
Offset Voltage
TL/H/11123– 4
4
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