Datasheet

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LM1973

www.ti.com

SNAS093B –DECEMBER 1994–REVISED MARCH 2013

LM1973 µPot 3-Channel 76dB Audio Attenuator with Mute

Check for Samples: LM1973

FEATURES

DESCRIPTION

The LM1973 is a digitally controlled 3-channel 76dB

• 3-Wire Serial Interface

audio attenuator fabricated on a CMOS process.

• Daisy-Chain Capability

Each channel has attenuation steps of 0.5dB from

• 104dB Mute Attenuation

0dB–15.5dB, 1.0dB steps from 16dB–47dB, and

2.0dB steps from 48dB– 76dB, with a mute function

• Pop and Click Free Attenuation Changes

attenuating 104dB. Its logarithmic attenuation curve

can be customized through software to fit the desired

APPLICATIONS

application.

• Automated Studio Mixing Consoles

The performance of a μPot is demonstrated through

• Music Reproduction Systems

its excellent Signal-to-Noise Ratio, extremely low

• Sound Reinforcement Systems

(THD+N), and high channel separation. Each μPot

contains a mute function that disconnects the input

• Electronic Music (MIDI)

signal from the output, providing a minimum

• Personal Computer Audio Control

attenuation of 96dB. Transitions between any

attenuation settings are pop free.

KEY SPECIFICATIONS

The LM1973's 3-wire serial digital interface is TTL

• Total Harmonic Distortion + Noise: 0.003 %

and CMOS compatible; receiving data that selects a

(max)

channel and the desired attenuation level. The Data-

Out pin of the LM1973 allows multiple μPots to be

• Frequency response: 100 kHz (−3dB) (min)

daisy-chained together, reducing the number of

• Attenuation range (excluding mute): 76 dB

enable and data lines to be routed for a given

(typ)

application.

• Differential attenuation: ±0.25 dB (max)

• Signal-to-noise ratio (ref. 4 Vrms): 110 dB

(min)

• Channel separation: 110 dB (typ)

TYPICAL APPLICATION

CONNECTION DIAGRAM

Top View

Figure 1. Typical Audio Attenuator

Application Circuit

Figure 2. PDIP and SOIC Packages

See Package Numbers NFH0020A and DW0020B

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.

2All 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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LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 LM1973 µPot 3-Channel 76dB Audio Attenuator with Mute Check for Samples: LM1973 FEATURES DESCRIPTION • • • • The LM1973 is a digitally controlled 3-channel 76dB audio attenuator fabricated on a CMOS process. Each channel has attenuation steps of 0.5dB from 0dB–15.5dB, 1.0dB steps from 16dB–47dB, and 2.0dB steps from 48dB– 76dB, with a mute function attenuating 104dB.
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LM1973 SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 www.ti.com 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–VSS) 15V VSS − 0.2V to VDD + 0.
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LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 ELECTRICAL CHARACTERISTICS (1) (2) The following specifications apply for all channels with VDD = +6V, VSS = −6V, VIN = 5.5 Vpk, and f = 1 kHz, unless otherwise specified. Limits apply for TA = 25°C. Digital inputs are TTL and CMOS compatible. Parameter Test Conditions IS Supply Current Inputs are AC Grounded THD+N Total Harmonic Distortion plus Noise VIN = 0.
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LM1973 SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 www.ti.com TEST CIRCUIT DIAGRAMS Figure 3. Timing Diagram PIN DESCRIPTIONS Signal Ground (1, 5, 17): Each input has its own independent ground, GND1, GND2, and GND3. Signal Input (2, 4, 18): There are 3 independent signal inputs, IN1, IN2, and IN3. Signal Output (6, 16, 20): There are 3 independent signal outputs, OUT1, OUT2, and OUT3. Voltage Supply (13, 15): Voltage Supply (7, 19): Negative voltage supply pins, VSS1 and VSS2.
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LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Supply Voltage Supply Current vs Temperature Figure 4. Figure 5. Noise Floor Spectrum by FFT Amplitude vs Frequency THD vs Freq by FFT VDD − VSS = 12V Figure 6. Figure 7. THD vs VOUT at 1 kHz by FFT VDD − VSS = 12V Crosstalk Test Figure 8. Figure 9.
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LM1973 SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) 6 THD + N vs Frequency and Amplitude FFT of 1 kHz THD Figure 10. Figure 11. FFT of 20 kHz THD THD + N vs Amplitude f = 20 Hz, VDD = ±6V VIN into CH1 at 0 dB Figure 12. Figure 13. THD + N vs Amplitude f = 1 kHz, VDD = ±6V VIN into CH1 at 0 dB THD + N vs Amplitude f = 20 kHz, VDD = ±6V VIN into CH1 at 0 dB Figure 14. Figure 15.
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LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 APPLICATION INFORMATION ATTENUATION STEP SCHEME The fundamental attenuation step scheme for the LM1973 μPot is shown in Figure 16. 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 2dB steps for a panning function as shown in Figure 18.
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LM1973 SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 www.ti.com LM1973 Channel Attenuation vs Digital Step Value (Programmed 2.0dB Steps) Figure 18. LM1973 2.0dB Attenuation Step Scheme Figure 19. Mono Level Control with Panning Circuit INPUT IMPEDANCE The input impedance of a μPot is constant at a nominal 40 kΩ. To eliminate any unwanted DC components from propagating through the device it is common to use 1 μF input coupling caps.
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LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 The mute function is obtained during power-up of the device or by sending any binary data of 01001111 and above (to 11111111) serially to the device. The device may be placed into mute from a previous attenuation setting by sending any of the above data. This allows the designer to place a mute button onto his system which could cause a microcontroller to send the appropriate data to a μPot and thus mute any or all channels.
PAGE 10
LM1973 SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 www.ti.com Table 1. LM1973 Micropot Attenuator Register Set Description (continued) MSB: LSB Address Register (Byte 0) ::::: :: 0011 1110 46.0 0011 1111 47.0 0100 0000 48.0 0100 0001 50.0 0100 0010 52.0 ::::: :: 0100 1100 72.0 0100 1101 74.0 0100 1110 76.0 0100 1111 100.0 (Mute) 0101 0000 100.0 (Mute) ::::: :: 1111 1110 100.0 (Mute) 1111 1111 100.
PAGE 11
LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 DIGITAL DATA-OUT PIN The DATA-OUT pin is available for daisy-chain system configurations where multiple μPots will be used. The use of the daisy-chain configuration allows the system designer to use only one DATA and one LOAD/SHIFT line per chain, thus simplifying PCB trace layouts.
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LM1973 SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 www.ti.com of DC bias current for its operation. As the impedance changes, so does the DC bias current and thus there is a DC voltage “pop”. 2. Secondly, the μPot has no drive capability, so any desired gain needs to be accomplished through a buffer/non-inverting amplifer. 3. Third, the output of a μPot needs to see a high impedance to prevent loading and subsequent linearity errors from ocurring.
PAGE 13
LM1973 www.ti.com SNAS093B – DECEMBER 1994 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision A (March 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 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
PAGE 16
PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM1973MX/NOPB Package Package Pins Type Drawing SOIC DW 20 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 1000 330.0 24.4 Pack Materials-Page 1 10.9 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 13.3 3.25 12.0 24.
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PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM1973MX/NOPB SOIC DW 20 1000 367.0 367.0 45.
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