NTE789 Integrated Circuit Stereo Multiplex Decoder

NTE789 Integrated Circuit Stereo Multiplex Decoder
NTE789
Integrated Circuit
Stereo Multiplex Decoder
Description:
The NTE789, a monolithic silicon integrated circuit, is a stereo multiplex decoder intended for FM multiplex
systems.
This stereo multiplex decoder requires only one low–inductance tuning coil (requires only one adjustment for
complete alignment), provides automatic stereo switching, energizes a stereo indicator lamp, and operates
from a wide range of voltage supplies.
Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a low–distortion preamplifier and simultaneously applied to both signal, generated by a local voltage–controlled oscillator (VCO), is counted down by two frequency dividers to a 38kHz signal and to two 19–kHz pilot–tone supplied
by the FM detector is compared to the locally generated 19–kHz signal in a synchronous detector.
The resultant signal controls the voltage controlled oscillator (VC)) so that it produces an output signal to
phase–lock the stereo decoder with the pilot tone. A second sychronous detector compares the locally generated 19–kHz signal with the 19–kHz pilot tone. If the pilot tone exceeds and externally adjustable threshold
voltage, a Schmitt trigger circuit is energized. The signal from the Schmitt trigger lights the stereo indicator,
enables the 38–kHz synchronous detector, and automatically switches the NTE789 form monaural to stereo
operation. The output signal from the 38–kHz detector and the composite signal from the preamplifier are applied to a matrixing circuit from which emerge the resultant left and right channel audio signals. These signals
are applied to their respective left and right post amplifiers for amplification to a level sufficient to drive most
audio amplifiers.
The NTE789 utilizes the 16–lead quad–in–line plastic package and operates over the ambient temperature
range of –40°C to +85°C.
Features:
D Requires the use of only one low–inductance tuning coil
D Automatic stereo switching
D Directly drives a stereo indicator lamp up to 100mA
D Includes driver for stereo–lamp indicator
D Operates from a wide range of power supplies: 10 to 16 volts
D Requires only one adjustment for alignment
D Switching from monaural to stereo and stereo to monaural produces no audible thumps
D Low distortion: under 0.5%
D Separate dc input permits stereo defeat or enable
D High signal output: directly drives audio amplifiers
D Excellent SCA (storecast) rejection: 55dB typ.
D High audio channel separation: 40dB typ.
Absolute Maximum Ratings: (TA = +25°C unless otherwise specified)
DC Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16V
Current at Pin12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100mA
Input Signal Voltage (Composite)(Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400mV
Operating Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40 to +85°C
Storage Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65 to +150°C
Lead Temperature (During Soldering, 1/32” (0.79mm) from case,10s max.) . . . . . . . . . . . . . . . . . . . . . +265°C
Note 1. For stereo operation, a minimum input signal voltage (composite) of 40mV is required.
Electrical Characteristics: (TA = +25°C, V+ = 12 unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
–
22
27
mA
V1
1.6
2.3
3.1
V
V6
–
2.1
3.6
V
V9, V10
3.7
5.4
7.4
V
12.7
–
–
V
–
0
0.1
V
75
100
–
mA
–
50k
–
Ω
Static Characteristics
Total Current (Pin9, Pin10,Pin11)
DC Voltage
Pin1
Pin6 (Indicator Lamp OFF)
Pin9 and Pin10
Pin12 (Indicator Lamp OFF)
Voltage Differential (Pin2 – Pin1)
Itotal
V12
Lamp OFF
V+ = 16V
V2 – V1
Current at Pin12
(In actual use external circuit
resistance (e.g. lamp should limit
Pin12 to the maximum rated value
of 100mA)
VIN (at f = 19kHz) = 18mV
Static Characteristics
Input Impedance
Zin
Channel Separatiom (L + R Reference)
VIN = 180mV, Note 3
25
40
–
dB
Channel Balance (Monaural)
VIN = 180mV
–
0.3
3.0
dB
Monaural Gain
VIN = 180mV
3
6
9
dB
Stereo/Monaural Gain Ratio
VIN = 180mV, Note 3
–
±0.3
±3.0
dB
Indicator Lamp – Turn–ON Voltage
19kHz pilot–tone at Pin1
–
4
–
mV
Capture Range
(Deviation from 76kHz center
frequency)
19kHz pilot–tone voltage = 18mV
±6.6
±10
–
%
–
0.2
–
%
–
< 0.1
–
%
19kHz Rejection
–
35
–
dB
38kHz Rejection
–
25
–
dB
SCA (Storecast) Rejection
–
55
–
dB
Stereo Defeat Voltage (V4)
–
–
< 0.9
V
Stereo Enable Voltage (V4)
> 1.6
–
–
V
Distortion (75µs De–emphasis)
2nd Harmonic
3rd,
4th,
and
5th
Harmonic
VIN = 240mV
Note 2. For improved pilot sensitivity and overload characteristics, replace the .039µF capacitor between Pin7
and Pin8 with a Series L–C Network (L = 4.7mH, C = 0.015µF). Under these conditions, Indicator
Lamp Sensitivity: “ON” = 3.3mV, “OFF” = 2.0mV.
Note 3. For stereo operation, test conditions require a composite stereo input signal (modulated at 1kHz) including a 19kHz (18mV) pilot–tone signal.
Pin Connection Diagram
GND 4
Indicator Input
16 76kHz Network
Capacitor Input
15 76kHz Network
14 Phase Lock Filter
Loop Network
13 GND
GND 5
12 Lamp Drive Circuit
Composite FM 1
Detected Signal Input
Bypass 2
GND 3
11 (+) VCC
RC Network 6
19kHz Pilot Lamp 7
10 Right Ch Output
9 Left Ch Output
Sensitivity Network 8
.012
(0.30)
.250
(6.35)
16
9
1
8
.300
(7.62)
.099 (2.51) Min
.785 (19.9) Max
.200 (5.08) Max
.020 (.508)
.100 (2.54)
.700 (17.78)
.400 (10.16)
.200 (5.08)
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