LMF380 [NSC]
LMF380 Triple One-Third Octave Switched-Capacitor Active Filter; LMF380三重三分之一倍频开关电容有源滤波器
| 型号： | LMF380 |
| 厂家： | 
National Semiconductor |
| 描述： | LMF380 Triple One-Third Octave Switched-Capacitor Active Filter |
| 文件： | 总12页 (文件大小：234K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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 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.
Accuracy is enhanced by close matching of the internal
components: the ratio of the clock frequency to the center
g
frequency is typically accurate to 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 fre-
quency spacing
Y
Choice of internal or external clock
Y
No external components other than clock or crystal and
two capacitors
Key Specifications
Y
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
Passband gain accuracy: Better than 0.7 dB over
temperature
Y
a
a
Supply voltage range: 2V to 7.5V or 4V to 14V
g
g
d
LMF380 has an internal clock frequency divider ( 2) and
Applications
Y
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.
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
TL/H/11123
RRD-B30M115/Printed in U. S. A.
Absolute Maximum Ratings (Notes 1 & 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Power Dissipation (Note 5)
Maximum Junction Temperature
Storage Temperature Range
ESD Susceptibility (Note 6)
500 mW
150 C
§
b
a
65 C to 150 C
§
§
2000V
b
a
0.3V to 16V
Total Supply Voltage
a
b
a
g
Voltage at Any Pin
Vb
0.3V to V
0.3V
Input Current per Pin (Note 3)
Total Input Current (Note 3)
5 mA
Operating Ratings (Note 1)
Temperature Range
g
20 mA
s
s
T
T
MIN
T
A
A
MAX
Lead Temperature (Soldering 10 sec.)
Dual-In-Line Package (Plastic)
LMF380CIN, LMF380CIV,
LMF380CIJ
s
s
a
b
b
a
85 C
40 C
T
300 C
§
§
55 C
§
s
s
LMF380CMJ
Supply Voltage (Va
T
125 C
§
§
A
Surface Mount Package (Note 4)
Vapor Phase (60 seconds)
Infrared (15 seconds)
b
b
V
)
4.0V to 14V
10 Hz to 1.25 MHz
215 C
§
220 C
§
Clock Input Frequency
b
Filter Electrical Characteristics The following specifications apply for Va
5V, V
e a
; all other limits apply for T
e b
5V, and f
CLK
25 C.
§
e
e
e
T
J
320 kHz unless otherwise specified. Boldface limits apply for T
MIN
to T
MAX
A
Typical
(Note 7)
Limit
(Note 8)
Units
Symbol
Parameter
Conditions
(Limit)
f
f
f
Clock-to-Center-Frequency Ratio, Filter 1
Clock-to-Center-Frequency Ratio, Filter 2
Clock-to-Center-Frequency Ratio, Filter 3
50:1
62.5:1
80:1
CLK:f01
CLK:f02
CLK:f03
e
1
A
A
A
A
A
A
A
V
Gain at f
3720 Hz (Filter 1),
(Note 9)
(Note 9)
(Note 9
(Note 9)
(Note 9)
(Note 9)
(Note 9)
1
b
a
b
30
32
dB (max)
dB (max)
dB (max)
dB (max)
dB (max)
dB (max)
dB (max)
2960 Hz (Filter 2), 2340 Hz (Filter 3)
e
Gain at f
2
6080 Hz (Filter 1),
2
g
0.1 0.7
0.1
4820 Hz (Filter 2), 3820 Hz (Filter 3)
e
Gain at f
3
6200 Hz (Filter 1),
3
b
g
0.0 0.7
0.0
4960 Hz (Filter 2), 3940 Hz (Filter 3)
e
Gain at f
4
6400 Hz (Filter 1),
4
b
b
b
b
g
0.2 0.7
0.2
0.1
5080 Hz (Filter 2), 4040 Hz (Filter 3)
e
Gain at f
5
6540 Hz (Filter 1),
5
g
0.1 0.7
5180 Hz (Filter 2), 4120 Hz (Filter 3)
e
Gain at f
6
6720 Hz (Filter 1),
6
a
b
0.15 0.7
g
0.15
5340 Hz (Filter 2), 4240 Hz (Filter 3)
e
Gain at f
7
8900 Hz (Filter 1),
7
b
b
20
22
50
7060 Hz (Filter 2), 5600 Hz (Filter 3)
a
a
Output Offset Voltage, Each Filter
120
mV (max)
mV (min)
OS
b
30
En
Total Output Noise, OUT1
Total Output Noise, OUT2
Total Output Noise, OUT3
0.1 Hz to 20 kHz
240
210
190
mVrms
C
L
Maximum Capacitive Load
Crosstalk
200
pF
dB
e
e
b
67
V
IN
1 Vrms, f
f
O
b
Va
5V, V
5 kX
10
mV
p-p
e a
e b
5V
Clock Feedthrough, Each Filter
Output Voltage Swing
e
a
b
a
b
V
OUT
R
L
4.2
4.6
3.8
4.2
V (min)
V (max)
e
e
f
O
THD
Total Harmonic Distortion
Supply Current
V
IN
1 Vrms, f
0.05
6.0
%
I
9.0
mA (max)
S
2
Logic Input and Output Electrical Characteristics
b
The following specifications for Va
5V and V
e a
25 C.
to
MIN
e a
e b
5V unless otherwise specified. Boldface limits apply for T
e
T
; all other limits apply for T
MAX
T
J
§
A
Tested
Typical
(Note 7)
Units
Symbol
Parameter
Conditions
Limit
(Limit)
(Note 8)
b
e
e b
a
b
V
XTAL1
Logical ‘‘1’’
Logical ‘‘0’’
Va
Va
Va
Va
I
5V, V
5V
3.0
3.0
V (min)
V (max)
IH
V
CMOS Clock
Input Voltage
IL
b
e
e
e
e
a
a
V
V
Logical ‘‘1’’
Logical ‘‘0’’
10V, V
2.5V, V
0V
8.0
2.0
V (min)
V (max)
IH
IL
b
e b
a
b
V
V
Logical ‘‘1’’
Logical ‘‘0’’
2.5V
1.5
1.5
V (min)
V (max)
IH
IL
b
e
a
a
V
V
Logical ‘‘1’’
Logical ‘‘0’’
5V, V
0V
4.0
1.0
V (min)
V (max)
IH
IL
e b
b
a
V
V
Clock Output Logical ‘‘1’’
Clock Output Logical ‘‘0’’
1 mA
e a
Va
Vb
1.0
1.0
V (min)
V (max)
OH
OUT
OUT
I
1 mA
OL
g
I
Input Current XTAL1
20
mA (max)
IN
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 Characteris-
tics. 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.
b or V
IN
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.
a), the current at that pin should be limited to 5 mA. The 20 mA
k
l
V
Note 3: When the input voltage (V ) at any pin exceeds the power supplies (V
IN IN
V
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
b
T
, i , and the ambient temperature, T . The
JA
)/i or the number given in the Absolute Maximum Ratings, whichever is lower.
A JA
Jmax
A
e
maximum allowable power dissipation at any temperature is P
(T
D
Jmax
e
For guaranteed operation, T
Jmax
125 C. The typical thermal resistance (i ) of the LMF380N when board-mounted is 51 C.W. i is typically 52 C/W for the
§ § §
JA JA
LMF380J, and 86 C/W for the LMF380V.
§
Note 6: Human body model, 100 pF discharged through a 1.5 kX resistor.
e
Note 7: Typicals are at T
25 C and represent the most likely parametric norm.
§
Note 8: Limits are guaranteed to National’s Averge Outgoing Quality Level (AOQL).
J
e
frequencies listed in the table may differ slightly from the nominal values.
e
e
e
e
e
e
1.05 f , and f 1.39 f . The actual test
7
Note 9: The nominal test frequencies are: f
0.58 f , f
O
0.95 f , f
O
0.98 f , f
O
f
, f
O
1.02 f , f
O
1
2
3
4
5
6
O
O
3
Typical Performance Characteristics
Power Supply Current
vs Power Supply Voltage
Power Supply Current
vs Temperature
Positive Output Swing
vs Load Resistance
TL/H/11123–4
4
1.0 mF to 10.0 mF tantalum capacitor
should also be used. For single-supply op-
eration, connect this pin to system ground.
Connection Diagrams
Dual-In-Line Package
CLOCK OUT This is the clock output pin. It can drive the
clock inputs (XTAL1) of additional LMF380s
or other components. The clock output fre-
quency is one-half the clock frequency at
XTAL1.
INPUT1,
INPUT2,
INPUT3
These are the signal inputs to the filters.
Va
This is the positive power supply pin. It
should be bypassed with at least a 0.1 mF
ceramic capacitor. For best results, a 1.0
mF to 10.0 mF tantalum capacitor should
also be used.
TL/H/11123–2
Top View
Order Number LMF380CIJ, LMF380CMJ or LMF380CIN
See NS Package Number J16A or N16E
Functional Description
The LMF380 contains three fourth-order Chebyshev band-
pass filters whose center frequencies are spaced one-third
of an octave apart, making it ideal for use in ‘‘real time’’
audio spectrum analysis applications. As with other
switched-capacitor filters, the center frequencies are pro-
portional to the clock frequency applied to the IC; the center
frequencies of the LMF380’s three filters are located at
Plastic Chip Carrier Package
f /50, f
CLK
/62.5, and f
CLK
/80.
CLK
The three filters in an LMF380 cover a full octave in fre-
quency, so that by using several LMF380s with clock fre-
quencies separated by a factor of 2n, a complex audio pro-
gram can be analyzed for frequency content over a range of
several octaves. To facilitate this, the CLK OUT pin of the
LMF380 supplies an output clock signal whose frequency is
one-half that of the incoming clock frequency. Therefore, a
single clock source can provide the clock reference for all of
the 30 filters (10LMF380s) in a real time analyzer that cov-
ers the entire 10-octave audio frequency range. The
LMF380 contains an internal clock oscillator that requires
an external crystal and two capacitors to operate. Since the
clock divider is on-board, only a single crystal is needed for
the top-octave filter chip; the remaining devices can derive
their clock signals from the master. If desired, an external
oscillator can be used instead.
TL/H/11123–3
Top View
Order Number LMF380CIV
See NS Package Number V20A
Pin Description
GND
This is the analog ground reference for the
LMF380. In split supply applications, GND
should be connected to the system ground.
When operating the LMF380 from a single
positive power supply voltage, pin 1 should
be connected to a ‘‘clean’’ reference volt-
Figure 1 shows the magnitude versus frequency curves for
the three filters in the LMF380. Separate input and output
pins are provided for the three internal filters. The input pins
will normally be connected to a common signal source, but
can also be connected to separate input signals when nec-
essary.
age midway between Va and Vb
.
N.C.
These pins are not connected to the inter-
nal circuitry.
OUT1, OUT2, These are the outputs of the filters.
OUT3
XTAL1
This is the crystal oscillator input pin. When
using the internal oscillator, the crystal
should be tied between XTAL1 and XTAL2.
XTAL1 also serves as the input for an exter-
nal CMOS-level clock.
XTAL2
This is the output of the internal crystal
oscillator. When using the internal oscilla-
tor, the crystal should be tied between
XTAL1 and XTAL2.
Vb
This is the negative power supply pin. It
should be bypassed with at least a 0.1 mF
TL/H/11123–6
FIGURE 1. Response curves for the three filters in the
LMF380. The clock frequency is 250 kHz.
ceramic capacitor. For best results,
a
5
Applications Information
POWER SUPPLIES
The LMF380 can operate from a total supply voltage (Va
b
Vb) ranging from 4.0V up to 14V, but the choice of supply
voltage can affect circuit performance. The IC depends on
MOS switches for its operation. All such switches have in-
herent ‘‘ON’’ resistances, which can cause small delays in
charging internal capacitances. Increasing the supply volt-
age reduces this ‘‘ON’’ resistance, which improves the ac-
curacy of the filter in high-frequency applications. The maxi-
mum practical center frequency improves by roughly 10% to
20% when the supply voltage increases from 5V to 10V.
TL/H/11123–8
FIGURE 2. Switched-Capacitor Filter Output Waveform.
Note the sampling ‘‘steps’’.
Dynamic range is also affected by supply voltage. The maxi-
mum signal voltage swing capability increases as supply
voltage increases, so the dynamic range is greater with
higher power supply voltages. It is therefore recommended
that the supply voltage be kept near the maximum operating
voltage when dynamic range and/or high-frequency per-
formance are important.
ALIASING
Another important characteristic of sampled-data systems is
their effect on signals at frequencies greater than one-half
the sampling frequency, f . (The LMF380’s sampling fre-
S
quency is the same as the filter clock frequency). If a signal
with a frequency greater than one-half the sampling fre-
quency is applied to the input of a sampled-data system, it
will be ‘‘reflected’’ to a frequency less than one-half the
sampling frequency. Thus, an input signal whose frequency
As with all switched-capacitor filters, each of the LMF380’s
power supply pins should be bypassed with a minimum of
0.1 mF located close to the chip. An additional 1 mF to
10 mF tantalum capacitor on each supply pin is recommend-
ed for best results.
a
the input frequency was f /2
is f /2
S
10 Hz will cause the system to respond as though
b
10 Hz. If this frequency
S
Sampled-Data System
Considerations
CLOCK CIRCUITRY
happens to be within the passband of the filter, it will appear
at the filter’s output, even though it was not present in the
input signal. This phenomenon is known as ‘‘aliasing’’. Ali-
asing can be reduced or eliminated by limiting the input sig-
The LMF380’s clock input circuitry accepts an external
CMOS-level clock signal at XTAL1, or can serve as a self-
contained oscillator with the addition of an external 1 MHz
crystal and two 30 pF capacitors (see Figure 3 ).
nal spectrum to less than f /2. In some cases, it may be
S
necessary to use a bandwidth-limiting filter (often a simple
passive RC low-pass) between the signal source and the
switched-capacitor filter’s input. In the application example
shown inFigure 3, two LMF60 6th-order low-pass filters pro-
vide anti-aliasing filtering.
The Clock Output pin provides a clock signal whose fre-
quency is one-half that of the clock signal at XTAL1. This
allows multiple LMF380s to operate from a single internal or
external clock oscillator.
OFFSET VOLTAGE
Switched-capacitor filters often have higher offset voltages
than non-sampling filters with similar topologies. This is due
to charge injection from the MOS switches into the sampling
and integrating capacitors. The LMF380’s offset voltage
CLOCK FREQUENCY LIMITATIONS
The performance characteristics of a switched-capacitor fil-
ter depend on the switching (clock) frequency. At very low
clock frequencies (below 10 Hz), the time between clock
cycles is relatively long, and small parasitic leakage currents
cause the internal capacitors to discharge sufficiently to af-
fect the filter’s offset voltage and gain. This effect becomes
more pronounced at elevated operating temperatures.
b
ranges from a minimum of
a
30 mV to a maximum of
120 mV.
NOISE
Switched-capacitor filters have two kinds of noise at their
outputs. There is a random, ‘‘thermal’’ noise component
whose amplitude is typically on the order of 210 mV. The
other kind of noise is digital clock feedthrough. This will
have an amplitude in the vicinity of 10 mV peak-to-peak. In
some applications, the clock noise frequency is so high
compared to the signal frequency that it is unimportant. In
other cases, clock noise may have to be removed from the
output signal with, for example, a passive low-pass filter at
the LMF380’s output (see Figure 4 ).
At higher clock frequencies, performance deviations are
due primarily to the reduced time available for the internal
operational amplifiers to settle. For this reason, when the
filter clock is externally generated, care should be taken to
ensure that the clock waveform’s duty cycle is as close to
50% as possible, especially at high clock frequencies.
OUTPUT STEPS
Because the LMF380 uses switched-capacitor techniques,
its performance differs in several ways from non-sampled
(continuous) circuits. The analog signal at any input is sam-
pled during each filter clock cycle, and since the output volt-
age can change only once every clock cycle, the result is a
discontinuous output signal. The output signal takes the
form of a series of voltage ‘‘steps’’, as shown in Figure 2 for
clock-to-center-frequency ratios of 50:1 and 100:1.
INPUT IMPEDANCE
The LMF380’s input pins are connected directly to the inter-
nal biquad filter sections. The input impedance is purely ca-
pacitive and is approximately 6.2 pF at each input pin, in-
cluding package parasitics.
6
Typical Applications
TL/H/11123–7
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 dual-in-line package.
7
Typical Applications (Continued)
tional to the peak signal voltage, it provides a good indica-
tion of the voltage swing. Generally, the output of the peak
detector must have a moderately fast (about 1 ms) attack
time and a much slower (tens or hundreds of milliseconds)
decay time. The actual attack and decay times depend on
the expected application. An average detector responds to
the average value of the rectified input signal and provides a
good solution when measuring random noise. An average
detector will normally respond relatively slowly to a rapid
change in input amplitude. An rms detector gives an output
that is proportional to signal power, and is therefore useful
in many instrumentation applications, especially those that
involve complex signals.
THIRD-OCTAVE ANALYZER FILTER SET
The circuit shown in Figure 3 uses the LMF380 to imple-
ment a (/3-octave filter set for use in ‘‘real time’’ audio pro-
gram analyzers. Ten LMF380s provide all of the bandpass
filtering for the full audio frequency range. The power supply
connections are not shown, but each power supply pin
should be bypassed with a 0.1 mF ceramic capacitor in par-
allel with a 1 mF tantalum capacitor.
The first LMF380, at the top ofFigure 3, handles the highest
octave, with center frequencies of 20 kHz, 16 kHz, and
12.6 kHz. It also contains the 1 MHz master clock oscillator
for the entire system. Its Clock Out pin provides a 500 kHz
clock for the second LMF380, which supplies 250 kHz to
the third LMF380, and so on.
Peak detectors and average-responding detectors require
precision rectifiers to convert the bipolar input signal into a
unipolar output. Half-wave rectifiers are relatively inexpen-
sive, but respond to only one polarity of input signal; there-
fore, they can potentially ignore information. Full-wave recti-
fiers need more components, but respond to both polarities
of input signal. Examples of half- and full-wave peak- and
average-responding detectors are shown in Figure 4. The
component values shown may need to be adjusted to meet
the requirements of a particular application. For example,
peak detector attack and decay times may be changed by
changing the value of the ‘‘hold’’ capacitor.
If the audio input signal were applied to all of the LMF380
input pins, aliasing might occur in the lower frequency filters
due to audio components near their clock frequencies. For
example, the LMF380 at the bottom of Figure 3 has a clock
frequency equal to 1.953125 kHz. An input signal at
1.93 kHz will be aliased down to 23.125 Hz, which is near
the band center of the 24.4 Hz bandpass filter and will ap-
pear at the output of that filter.
This problem is solved by two LMF60–100 6th order Butter-
worth low-pass filters serving as anti-aliasing filters, as
shown in Figure 3. The first LMF60–100 is connected to the
input signal. The clock for this LMF60 is 250 kHz and comes
from pin 10 of the second LMF380. The cutoff frequency is
therefore 2.5 kHz. The output of this first LMF60–100 drives
the inputs of the fifth, sixth, and seventh LMF380s. The sev-
enth LMF380 has a 15.625 kHz clock, so aliasing will begin
to become a problem around 15.2 kHz. With a sixth-order,
2.5 kHz low-pass filter preceding this circuit, the attenuation
at 15.2 kHz is theoretically about 94 dB, which prevents
aliasing from occuring at this bandpass filter.
The input to each detector should be capacitively-coupled
as shown in Figure 4. This prevents any errors due to volt-
age offsets in the preceding circuitry. The cutoff frequency
of the resulting high-pass filter should be less than half the
center frequency of the band of interest.
Note that a passive low-pass filter is shown at the input to
each detector in Figure 4. These filters attenuate any clock-
frequency signals at the outputs of the third-octave
switched-capacitor filters. The typical clock feedthrough at a
filter output is 10 mV rms, or 40 dB down from a nominal
1 Vrms signal amplitude. When more than 40 dB dynamic
range is needed, a passive low-pass filter with a cutoff fre-
quency about three times the center frequency of the band-
pass will attenuate the clock feedthrough by about 24 dB,
yielding about 64 dB dynamic range. The component values
shown produce a cutoff frequency of 1 kHz; changing the
capacitor value will alter the cutoff frequency in inverse pro-
portion to the capacitance.
The output of the first LMF60 also drives the input of the
second LMF60, which provides anti-aliasing filtering for the
three LMF380s that handle the lowest part of the audio fre-
quency spectrum.
Note that no anti-aliasing filtering is provided for the four
LMF380s at the top of Figure 3. These devices will not en-
counter aliasing problems for frequencies below about
120 kHz; if higher input frequencies are expected, an addi-
tional low-pass filter at V may be required.
IN
The offset voltage of the operational amplifier used in the
detector will also affect the detector’s dynamic range. The
LF353 used in the circuits in Figure 3 is appropriate for sys-
tems requiring up to 40 dB dynamic range.
DETECTORS
In a real-time analyzer, the amplitude of the signal at the
output of each filter is displayed, usually in ‘‘bar-graph’’
form. The AC signal at the output of each bandpass filter
must be converted to a unipolar signal that is appropriate for
driving the display circuit.
DISPLAYS
The output of the detector will drive the input of the display
circuit. An example of an LED display driver using the
LM3915 is shown in Figure 5. The LM3915 drives 10 LEDs
with 3 dB steps between LEDs; the total display range for an
LM3915 is therefore 27 dB. Two LM3915s can be cascaded
to yield a total range of 57 dB. See the LM3915 data sheet
for more information.
The detector can take any of several forms. It can respond
to the peaks of the input signal, to the average value, or to
the rms value. The best type of detector depends on the
application. For example, peak detectors are useful when
monitoring audio program signals that are likely to overdrive
an amplifier. Since the output of the peak detector is propor-
8
Typical Applications (Continued)
(a)
(b)
TL/H/11123–9
TL/H/11123–10
(c)
TL/H/11123–11
(d)
TL/H/11123–12
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 noise from switched-capacitor filters; values shown are for 1 kHz cutoff frequency. C should be at
IN
least 0.27 mF for frequency bands below 50 Hz and 0.1 mF for higher frequencies. Power supplies (not shown) should
be bypassed with at least 0.1 mF close to the amplifiers.
9
Typical Applications (Continued)
TL/H/11123–13
FIGURE 5. LED display using LM3915 bar graph driver. The input voltage range is 2V full-scale, with 3 dB per step.
10
Physical Dimensions inches (millimeters)
Dual-In-Line Package (J)
Order Number LMF380C1J or LMF380CMJ
NS Package Number J16A
Dual-In-Line Package (N)
Order Number LMF380CIN
NS Package Number N16E
11
Physical Dimensions inches (millimeters) (Continued)
Plastic Chip Carrier Package (V)
Order Number LMF380CIV
NS Package Number V20A
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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. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and whose
failure to perform, when properly used in accordance
with instructions for use provided in the labeling, can
be reasonably expected to result in a significant injury
to the user.
2. A critical component is any component of a life
support device or system whose failure to perform can
be reasonably expected to cause the failure of the life
support device or system, or to affect its safety or
effectiveness.
National Semiconductor
Corporation
National Semiconductor
Europe
National Semiconductor
Hong Kong Ltd.
National Semiconductor
Japan Ltd.
a
1111 West Bardin Road
Arlington, TX 76017
Tel: 1(800) 272-9959
Fax: 1(800) 737-7018
Fax:
(
49) 0-180-530 85 86
@
13th Floor, Straight Block,
Ocean Centre, 5 Canton Rd.
Tsimshatsui, Kowloon
Hong Kong
Tel: (852) 2737-1600
Fax: (852) 2736-9960
Tel: 81-043-299-2309
Fax: 81-043-299-2408
Email: cnjwge tevm2.nsc.com
a
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Fran3ais Tel:
Italiano Tel:
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(
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(
49) 0-180-530 85 85
49) 0-180-532 78 32
49) 0-180-532 93 58
49) 0-180-534 16 80
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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