LM1971N National Semiconductor, LM1971N Datasheet

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LM1971N

Manufacturer Part Number
LM1971N
Description
Digitally Controlled 62 dB Audio Attenuator with/Mute
Manufacturer
National Semiconductor
Datasheet

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© 2002 National Semiconductor Corporation
LM1971Overture
Digitally Controlled 62 dB Audio Attenuator with/Mute
General Description
The LM1971 is a digitally controlled single channel audio
attenuator fabricated on a CMOS process. Attenuation is
variable in 1 dB steps from 0 dB to −62 dB. A mute function
disconnects the input from the output, providing over 100 dB
of attenuation.
The performance of the device is exhibited by its ability to
change attenuation levels without audible clicks or pops. In
addition, the LM1971 features a low Total Harmonic Distor-
tion (THD) of 0.0008%, and a Dynamic Range of 115 dB,
making it suitable for digital audio needs. The LM1971 is
available in both 8-pin plastic DIP or SO packages.
The LM1971 is controlled by a TTL/CMOS compatible 3-wire
serial digital interface. The active low LOAD line enables the
data input registers while the CLOCK line provides system
timing. Its DATA pin receives serial data on the rising edge of
each CLOCK pulse, allowing the desired attenuation setting
to be selected.
Key Specifications
n Total harmonic distortion
n Frequency response
Typical Application
Overture
is a trademark of National Semiconductor Corporation.
FIGURE 1. Typical Audio Attenuator Application Circuit
>
200 kHz (−3 dB) (typ)
DS012353
Audio Attenuator Series
0.0008% (typ)
n Attenuation range (excluding mute)
n Dynamic range
n Mute attenuation
Features
n 3-wire serial interface
n Mute function
n Click and pop free attenuation changes
n 8-pin plastic DIP and SO packages available
Applications
n Communication systems
n Cellular Phones and Pagers
n Personal computer audio control
n Electronic music (MIDI)
n Sound reinforcement systems
n Audio mixing automation
01235301
September 2002
www.national.com
102 dB (typ)
115 dB (typ)
62 dB (typ)

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LM1971N Summary of contents

Page 1

... Key Specifications n Total harmonic distortion > n Frequency response Typical Application FIGURE 1. Typical Audio Attenuator Application Circuit Overture ™ trademark of National Semiconductor Corporation. © 2002 National Semiconductor Corporation Audio Attenuator Series n Attenuation range (excluding mute) n Dynamic range n Mute attenuation Features n 3-wire serial interface ...

Page 2

... Connection Diagram www.national.com Dual-In-Line Plastic or Surface Mount Package 01235302 Top View Order Number LM1971M or LM1971N See NS Package Number M08A or N08E 2 ...

Page 3

... Pins Pins Pins )/θ or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM1971N and LM1971M when board mounted is 102˚ C/W and 167˚ C/W, respectively −65˚C to +150˚C (Notes 1, 2) ≤ T −40˚C ≤ MAX ...

Page 4

Pin Descriptions V IN (1): The V IN pin provides the reference for the REF REF analog input signal. This pin should be biased at half of the supply voltage shown in Figure 1 and Figure 6. ...

Page 5

Typical Performance Characteristics THD + N vs Freq and Amp THD + N vs Amplitude Mute Attenuation vs Frequency (Continued) Noise Floor Spectrum by FFT 01235314 01235316 01235318 5 01235315 THD + N vs Amplitude 01235317 THD vs Freq by ...

Page 6

Typical Performance Characteristics THD vs Freq by FFT Application Information SERIAL DATA FORMAT The LM1971 uses a 3-wire serial communication format that is easily controlled by a microcontroller. The timing for the 3-wire set, comprised of DATA, CLOCK, and LOAD ...

Page 7

Application Information *Note: Load and clock falling edges can be coincident, however, the clock falling edge cannot be delayed more than 20 ns from the falling edge of load preferrable that the falling edge of clock occurs before ...

Page 8

Application Information ATTENUATION STEP SCHEME The fundamental attenuation step scheme for the LM1971 is shown in Figure also possible to obtain any integer value attenuation step through programming, in addition to the 2 dB and 4 dB ...

Page 9

Application Information quency power supply fluctuations, a smaller capacitor (0.01 µF–0.1 µF) could be added in parallel to the 10 µF capacitor. FIGURE 6. Higher Performance Active Half-Supply Buffering FIGURE 7. Active Reference with Active Gain Buffering LOGARITHMIC GAIN AMPLIFIER ...

Page 10

Physical Dimensions unless otherwise noted 8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC www.national.com inches (millimeters) Order Number LM1971M NS Package Number M08A 10 ...

Page 11

... 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. inches (millimeters) unless otherwise noted (Continued) Order Number LM1971N 8-Lead (0.300" Wide) Molded Dual-In-Line Package NS Package Number N08E 2 ...

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