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LMC1982
Digitally-Controlled Stereo Tone and Volume Circuit with
Two Selectable Stereo Inputs
General Description
The LMC1982 is a monolithic integrated circuit that provides
volume, balance, tone (bass and treble), enhanced stereo,
and loudness controls and selection between two pairs of
stereo inputs. These functions are digitally controlled
through a three-wirecommunicationinterface. There are two
digital inputs for easy interface to other audio peripherals
such as stereo decoders. The LMC1982 is designed for line
level input signals (300 mV–2V) and has a maximum gain of
−0.5 dB. Volumeis set at minimum and tone controls are flat
when supply voltage is first applied.
Low noise and distortion result from using analog switches
and poly-silicon resistor networks in the signal path.
Additional tone control can be achieved using the LMC835
stereo 7-band graphic equalizer connected to the
LMC1982’s SELECT OUT/SELECT IN external processor
loop.
Features
n Low noise and distortion
n Two pairs of stereo inputs
December 1994
n Enhanced stereo function
n Loudness compensation
n 40 position 2 dB/step volume attenuator plus mute
n Independent left and right volume controls
n Low noise-suitable for use with DNR
reduction
n External processor loop
n Signal handling suitable for compact discs
n Pop-free switching
n Serially programmable: INTERMETAL bus (IM) interface
n 6V to 12V single supply operation
n 28 Pin DIP or PLCC package
®
and Dolby®noise
Applications
n Stereo television
n Music reproduction systems
n Sound reinforcement systems
n Electronic music (MIDI)
n Personal computer audio control
LMC1982 Digitally-Controlled Stereo Tone and Volume Circuit with Two Selectable Stereo Inputs
Block and Connection Diagrams
DS011028-1
DNR®is a registered trademark of National Semiconductor Corporation.
®
Dolby
is a registered trademark of Dolby Labs.
© 1999 National Semiconductor Corporation DS011028 www.national.com
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.
Supply Voltage (V
Voltage at any Pin GND − 0.2V to V
Input Current at any Pin (Note 3) 5 mA
Package Input Current (Note 3) 20 mA
Power Dissipation (Note 4) 500 mW
Junction Temperature +125˚C
Storage Temperature −65˚C to +150˚C
Lead Temperature
+
− GND) 15V
+
0.2V
N Package,
(Soldering, 10 Seconds) +260˚C
V Package,
(Vapor Phase, 60 Seconds) 215˚C
Infrared, (15 Seconds) 220˚C
ESD Susceptability (Note 5) 2 kV
+
Operating Ratings(Notes 1, 2)
Temperature Range T
LMC1982CIN, LMC1982CIV −40˚C ≤ TA≤ +85˚C
Supply Voltage Range (V
+−V−
) 6Vto12V
MIN
≤ TA≤ T
MAX
Electrical Characteristics
The following specifications apply for V
0 dB, treble=0 dB, enhanced stereo is off, and loudness is off unlessotherwise specified. All limits apply for T
+
=
=
9V, f
1 kHz, input signal (300 mV) applied to INPUT 1, volume=0 dB, bass
IN
=
=
T
+25˚C.
A
J
Symbol Parameter Conditions Typical Limit Unit
(Note 6) (Note 7) (Limit)
I
V
Supply Current 15 25 mA (max)
S
Input Voltage Clipping Level (1,.0%THD), 2.3 2.0 V
IN
rms
Select Out (Pins 6, 23)
THD Total Harmonic Distortion Left and Right channels;
Output Pins 13, 16
=
V
0.3 V
IN
V
IN
V
IN
V
IN
rms
=
f
100 Hz, 1 kHz, 10 kHz
IN
=
2.0 V
rms
=
f
100 Hz, 1 kHz
IN
=
2.0 V
rms
=
f
10 kHz
IN
=
0.5 V
rms
; 0.008 0.1
; 0.4 1.0
; 0.5 1.0
; Bass and Treble 0.07 0.5
%
%
%
%
(max)
(max)
(max)
(max)
Tone Controls Set at Maximum
=
V
IN
Attenuator at −20 dB, Bass and Treble 0.06 0.15
0.3 V
; Volume
rms
%
(max)
Tone Controls Set at Maximum
DC Shifts V
=
IN
; Between Any 2.0 4.0 mV (max)
0.3 V
rms
Two Adjacent Control Settings
=
V
IN
; 18 20 mV (max)
0.3 V
rms
All Mode and Input Positions
R
AC Output Impedance Pins 6, 23, (470Ω to Ground at Input) 150 200 Ω (max)
OUT
Pins 13, 16 26 40 Ω (max)
R
AC Input Impedance Pins 4, 5, 24, 25 50 72 kΩ (max)
IN
35 kΩ (min)
Volume Attenuator Range Pins 13, 16; Volume 0.5 1.5 dB (max)
Attenuation at 0100010XXX000000 (0 dB)
0100010XXX101XXX (80 dB); 80 78 dB (min)
(Relative to Attenuation at 82 dB (max)
the 0 dB Setting)
Volume Step Size All Volume Attenuation Settings
from 0100010XXX101XXX (80 dB) to 2.0 1.5 dB (min)
0100010XXX000000 (0 dB) (Note 9) 2.5 dB (min)
=
(min)
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Electrical Characteristics (Continued)
+
=
The following specifications apply for V
0 dB, treble=0 dB, enhanced stereo is off, and loudness is off unlessotherwise specified. All limits apply for T
Symbol Parameter Conditions Typical Limit Unit
Channel-to-Channel Volume All Volume Attenuation Settings
Tracking Error from 0100010XXX101XXX (80 dB)
Mute Attenuation V
Bass Gain Range f
Bass Tracking Error f
Bass Step Size f
Treble Gain Range f
Treble Tracking Error f
Treble Step Size f
Enhanced Stereo Cross
Coupling
Frequency Response V
Loudness Volume Attenuator=40 dB, Loudness
Signal-to-Noise Ratio V
Channel Balance All Volume Settings 0.2 1.0 dB (max)
Channel Separation Input Pins 4, 25: Output Pins 13, 16; 80 60 dB (min)
Input-Input Isolation 470Ω to AC Ground on Unused Input 95 60 dB (min)
PSSR Power Supply Rejection Ratio V
f
V
V
V
V
Clock Frequency 5.0 1.0 MHz
CLK
Logic “1” Input Voltage Pins 1, 27, 28 (IM Bus) 1.3 2.0 V (min)
IN(1)
Logic “0” Input Voltage Pins 1, 27, 28 (IM Bus) 0.4 0.8 V (max)
IN(0)
Logic “1” Output Voltage Pin 28 (IM Bus) 2.0 V (min)
OUT(1)
Logic “0” Output Voltage Pin 28 (IM Bus) 0.4 0.8 V (max)
OUT(0)
Note 1: AbsoluteMaximum Ratings indicate limits beyond which damage to the deivce may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. 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 specified with respect to ground.
Note 3: When the input voltage (V
limited to 5 mA or less. The 20 mA package input current limits the number of pins that can exceed the power supply voltages with 5 mA current limit to four.
) at any pin exceeds the power supply voltages (V
IN
=
9V, f
1 kHz, input signal (300 mV) applied to INPUT 1, volume=0 dB, bass
IN
=
=
T
+25˚C.
A
J
(Note 6) (Note 7) (Limit)
±
0.1
±
1.5 dB (min)
to 0100010XXX000000 (0 dB)
=
1.0 V
IN
IN
IN
IN
rms
=
100 Hz, Pins 13, 16
=
100 Hz, Pins 13, 16
=
100 Hz, Pins 13, 16 2.0 1.5 dB (min)
105 86 dB (max)
±
12
±
0.1
±
10.0 dB (min)
±
14.0 dB (max)
±
1.5 dB (max)
(Relative to Previous Level) 2.5 dB (max)
=
10 kHz, Pins 13, 16
IN
=
10 kHz, Pins 13, 16
IN
=
10 kHz, Pins 13, 16 2.0 1.5 dB (min)
IN
±
12
±
0.1
±
10.0 dB (min)
±
14.0 dB (max)
±
1.5 dB (max)
(Relative to Previous Level) 2.5 dB (max)
(Note 10) −4.4 −2.5 dB (min)
−6.9 dB (max)
Applied to Input 1 and Input 2;
IN
=
f
20 Hz − 20 kHz
IN
±
0.1
±
1.0 dB (max)
(Relative to Signal Amplitude at 1 kHz)
on (See
Figure 5
)
Gain at 100 Hz (Referenced 11.5 13.5 dB (max)
to Gain at 1 kHz) 9.5 dB (min)
Gain at 10 kHz (Referenced 6.5 8.5 dB (max)
to Gain at 1 kHz) 4.5 dB (min)
=
IN
Measured at 1 kHz, R
=
V
IN
+
=
, A Weighted, 95 90 dB (min)
1.0 V
1.0V
9V
rms
rms
; 200 mV
DC
(Note 8)
=
470Ω
S
, 100 Hz 32 28 dB (min)
rms
Sinewave Applied to Pin 26
(max)
Pins 2, 3 2.9 5.5 V (min)
Pins 2, 3 1.2 3.5 V (max)
<
IN
V−or V
>
V+) the absolute value of the current at that pin should be
IN
=
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Electrical Characteristics (Continued)
Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
allowable power dissipation is P
+125˚C, and the typical junction-to-ambient thermal resistance, when board mounted, is 67˚C/W.
Note 5: Human body model; 100 pF discharged through a 1.5 kΩ resistor.
Note 6: Typicals are at T
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 8: The Input-Input Isolation is tested by driving one input and measuring the output when the undriven input are selected.
Note 9: TheVolumeStepSize is defined as the change in attenuation between any two adjacent volume attenuation settings. The nominalVolumeStep Size is 2 dB.
Note 10: Enhanced Stereo Cross Coupling is a measure of the ratio between the undriven right channel output signal and the driven left channel output signal. It
is measured by driving the left inputs with a 300 mV
=
(T
D
=
+25˚C and represent the most likely parametric norm.
J
)/θJAor the number given in the Absolute Maximum Ratings, whichever is lower. For the LMC1982CIN, T
JMAX−TA
signal while the right inputs are grounded.
rms
, θJA, and the ambient temperature TA. The maximum
JMAX
JMAX
Typical Performance Characteristics
=
Supply Current
vs Supply Voltage
THD vs
Load Impedance
THD vs V
(V
OUT
IN
Constant)
DS011028-13
DS011028-16
Output Voltage
vs Supply Voltage
CCIR Output Noise
vs Volume Setting
THD vs Frequency
DS011028-14
DS011028-17
THD vs
Load Impedance
DS011028-15
Channel Separation
vs Frequency
DS011028-18
Mute Gain
vs Frequency
DS011028-19
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DS011028-20
DS011028-21
Typical Performance Characteristics (Continued)
Tone Control Response
with Equal Bass and
Treble Control Settings
DS011028-22
Loudness Response
vs Frequency
DS011028-23
Select Input Impedance
vs Frequency
DS011028-24
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