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PDF LM1972N Data sheet ( Hoja de datos )
| Número de pieza | LM1972N | |
| Descripción | Pot 2-Channel 78dB Audio Attenuator with Mute | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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April 1995
LM1972
µPot™ 2-Channel 78dB Audio Attenuator with Mute
General Description
The LM1972 is a digitally controlled 2-channel 78dB audio
attenuator fabricated on a CMOS process. Each channel
has attenuation steps of 0.5dB from 0dB–47.5dB, 1.0dB
steps from 48dB–78dB, with a mute function attenuating
104dB. Its logarithmic attenuation curve can be customized
through software to fit the desired application.
The performance of a µPot is demonstrated through its ex-
cellent Signal-to-Noise Ratio, extremely low (THD+N), and
high channel separation. Each µPot contains a mute function
that disconnects the input signal from the output, providing a
minimum attenuation of 96dB. Transitions between any at-
tenuation settings are pop free.
The LM1972’s 3-wire serial digital interface is TTL and
CMOS compatible; receiving data that selects a channel and
the desired attenuation level. The Data-Out pin of the
LM1972 allows multiple µPots to be daisy-chained together,
reducing the number of enable and data lines to be routed
for a given application.
Key Specifications
n Total Harmonic Distortion + Noise:
0.003% (max)
n Frequency response:
100 kHz (−3dB) (min)
n Attenuation range (excluding mute):
78dB (typ)
n Differential attenuation:
±0.25dB (max)
n Signal-to-noise ratio (ref. 4 Vrms):
110dB (min)
n Channel separation:
100dB (min)
Features
n 3-wire serial interface
n Daisy-chain capability
n 104dB mute attenuation
n Pop and click free attenuation changes
Applications
n Automated studio mixing consoles
n Music reproduction systems
n Sound reinforcement systems
n Electronic music (MIDI)
n Personal computer audio control
Typical Application
Connection Diagram
Dual-In-Line Plastic or
Surface Mount Package
DS011978-1
FIGURE 1. Typical Audio Attenuator Application Circuit
DS011978-2
Top View
Order Number LM1972M or LM1972N
See NS Package Number M20B or N20A
µPot™ and Overture™ are trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS011978
www.national.com
1 page  
Typical Performance Characteristics (Continued)
THD + N vs Amplitude
THD + N vs Amplitude
THD + N vs Amplitude
DS011978-24
Application Information
ATTENUATION STEP SCHEME
The fundamental attenuation step scheme for the LM1972
µPot is shown in Figure 3. This attenuation step scheme,
however, can be changed through programming techniques
to fit different application requirements. One such example
would be a constant logarithmic attenuation scheme of 1dB
steps for a panning function as shown in Figure 4. The only
restriction to the customization of attenuation schemes are
the given attenuation levels and their corresponding data
bits shown in Table 1. The device will change attenuation
levels only when a channel address is recognized. When
recognized, the attenuation level will be changed corre-
sponding to the data bits shown in Table 1. As shown in Fig-
ure 6, an LM1972 can be configured as a panning control
which separates the mono signal into left and right channels.
This circuit may utilize the fundamental attenuation scheme
of the LM1972 or be programmed to provide a constant 1dB
logarithmic attenuation scheme as shown in Figure 4.
LM1972 Channel Attenuation
vs Digital Step Value
DS011978-25
DS011978-26
LM1972 Channel Attenuation
vs Digital Step Value
(Programmed 1.0dB Steps)
DS011978-7
FIGURE 4. LM1972 1.0dB
Attenuation Step Scheme
LM1972 Channel Attenuation
vs Digital Step Value
(Programmed 2.0dB Steps)
DS011978-6
FIGURE 3. LM1972 Attenuation Step Scheme
DS011978-8
FIGURE 5. LM1972 2.0dB Attenuation Step Scheme
5 www.national.com
5 Page 
Notes
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 AND GENERAL
COUNSEL 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
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: [email protected]
www.national.com
National Semiconductor
Europe
Fax: +49 (0) 1 80-530 85 86
Email: [email protected]
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: [email protected]
National Semiconductor
Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
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.
11 Page | ||
| Páginas | Total 11 Páginas | |
| PDF Descargar | [ Datasheet LM1972N.PDF ] | |
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