Datasheet

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LM1971

www.ti.com

SNAS104B –FEBRUARY 1995–REVISED APRIL 2013

LM1971 Overture™ Audio Attenuator Series Digitally Controlled 62 dB Audio Attenuator

with/Mute

Check for Samples: LM1971

FEATURES

DESCRIPTION

The LM1971 is a digitally controlled single channel

• 3-Wire Serial Interface

audio attenuator fabricated on a CMOS process.

• Mute Function

Attenuation is variable in 1 dB steps from 0 dB to −62

• Click and Pop Free Attenuation Changes

dB. A mute function disconnects the input from the

output, providing over 100 dB of attenuation.

• 8-Pin Plastic PDIP and SOIC Packages

Available

The performance of the device is exhibited by its

ability to change attenuation levels without audible

APPLICATIONS

clicks or pops. In addition, the LM1971 features a low

Total Harmonic Distortion (THD) of 0.0008%, and a

• Communication Systems

Dynamic Range of 115 dB, making it suitable for

• Cellular Phones and Pagers

digital audio needs. The LM1971 is available in both

• Personal Computer Audio Control 8-pin plastic PDIP or SOIC packages.

• Electronic Music (MIDI)

The LM1971 is controlled by a TTL/CMOS compatible

3-wire serial digital interface. The active low LOAD

• Sound Reinforcement Systems

line enables the data input registers while the CLOCK

• Audio Mixing Automation

line provides system timing. Its DATA pin receives

serial data on the rising edge of each CLOCK pulse,

KEY SPECIFICATIONS

allowing the desired attenuation setting to be

selected.

• Total Harmonic Distortion 0.0008 % (Typ)

• Frequency Response > 200 kHz (−3 dB) (Typ)

• Attenuation Range (Excluding Mute) 62 dB

(Typ)

• Dynamic Range 115 dB (Typ)

• Mute Attenuation 102 dB (Typ)

Typical Application

Figure 1. Typical Audio Attenuator Application Circuit

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2Overture is a trademark of dcl_owner.

3All other trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (19 pages)

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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 LM1971 Overture™ Audio Attenuator Series Digitally Controlled 62 dB Audio Attenuator with/Mute Check for Samples: LM1971 FEATURES 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.
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LM1971 SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 www.ti.com Connection Diagram Figure 2. Dual-In-Line Plastic or Surface Mount Package- Top View These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) (3) Supply Voltage, VDD 15V (GND −0.2V) to (VDD +0.
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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 Electrical Characteristics (1) (2) The following specifications apply for VDD = +12V (VREFIN = +6V), VIN = 5.5 Vpk, and f = 1 kHz, unless otherwse specified. Limits apply for TA = 25°C. Digital inputs are TTL and CMOS compatible. Symbol Parameter Conditions LM1971 Typical (3) Limit (4) Units (Limits) IS Supply Current Digital Inputs Tied to 6V 1.8 3 mA (max) THD Total Harmonic Distortion VIN = 0.5Vpk@ 0 dB Attenuation 0.
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LM1971 SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 www.ti.com Pin Descriptions VREFIN (1): The VREFIN pin provides the reference for the analog input signal. This pin should be biased at half of the supply voltage, VDD, as shown in Figure 1 and Figure 19. OUT (2): The attenuated analog output signal comes from this pin. GND (3): The GND pin references the digital input signals and is the lower voltage reference for the IC.
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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 Typical Performance Characteristics Supply Current vs Supply Voltage Supply Current vs Temperature Figure 3. Figure 4. Noise Floor Analog Measurement THD + N vs Freq and Amp Figure 5. Figure 6. THD + N vs Freq and Amp Noise Floor Spectrum by FFT Figure 7. Figure 8.
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LM1971 SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) 6 THD + N vs Amplitude THD + N vs Amplitude Figure 9. Figure 10. Mute Attenuation vs Frequency THD vs Freq by FFT Figure 11. Figure 12. THD vs Freq by FFT Output Impedance vs Attenuation Level Figure 13. Figure 14.
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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 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 is shown in Figure 15. As depicted in Figure 15, the LOAD line is to go low at least 150 ns before the rising edge of the first clock pulse and is to remain low throughout the transmission of the 16 data bits.
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LM1971 SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 www.ti.com *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. It is preferrable that the falling edge of clock occurs before the falling edge of load. Figure 15. Timing Diagram Figure 16. Serial Data Format Transfer Process μPOT LADDER ARCHITECTURE The μPot contains a chain of R1/R2 resistor dividers in a ladder form, as shown in Figure 17.
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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 ATTENUATION STEP SCHEME The fundamental attenuation step scheme for the LM1971 is shown in Figure 18. It is also possible to obtain any integer value attenuation step through programming, in addition to the 2 dB and 4 dB steps shown in Figure 18. All higher attenuation step schemes can have clickless and popless performance.
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LM1971 SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 www.ti.com Attenuation level changes cause changes in the output impedance of a μPot. Output impedance changes in the presence of a large input bias current for a buffer/amplifier will cause a DC shift to occur. Neglecting amplifier gains and speaker sensitivities, the audibility of a DC shift is dependent upon the output impedance change times the required input bias current.
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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 Figure 20. Active Reference with Active Gain Buffering LOGARITHMIC GAIN AMPLIFIER The μPot is capable of being used in the feedback loop of an op amp to create a gain controlled amplifier as shown in Figure 21. In this configuration the attenuation levels from Table 1 become gain levels with the largest possible gain value being 62 dB. For most applications, 62 dB of gain will cause signal clipping to occur.
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LM1971 SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 www.ti.com DC INPUTS Although the μPot was designed to be used as an attenuator for signals within the audio spectrum, it is also capable of tracking and attenuating an input DC voltage. The device will track voltages to either supply rail. One point to remember about DC tracking is that with a buffer at the output of the μPot, the resolution of DC tracking will depend upon the gain configuration of that output buffer and its supply voltage.
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LM1971 www.ti.com SNAS104B – FEBRUARY 1995 – REVISED APRIL 2013 REVISION HISTORY Changes from Revision A (April 2013) to Revision B • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 18-Oct-2013 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM1971MX SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM1971MX/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM1971MX SOIC D 8 2500 367.0 367.0 35.0 LM1971MX/NOPB SOIC D 8 2500 367.0 367.0 35.
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