NTE NTE789 Datasheet

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

Static Characteristics

Total Current (Pin9, Pin10,Pin11) I
DC Voltage

Pin1
Pin6 (Indicator Lamp OFF) V
Pin9 and Pin10 V9, V
Pin12 (Indicator Lamp OFF) V

Voltage Differential (Pin2 – Pin1) V2 – V
Current at Pin12

(In actual use external circuit

resistance (e.g. lamp should limit

Pin12 to the maximum rated value

of 100mA)

total

V

Lamp OFF – 22 27 mA

1
6

10

V+ = 16V 12.7 – – V

12

1

VIN (at f = 19kHz) = 18mV 75 100 – mA

1.6 2.3 3.1 V
– 2.1 3.6 V

3.7 5.4 7.4 V

– 0 0.1 V

Static Characteristics

Input Impedance Z
Channel Separatiom (L + R Reference) VIN = 180mV, Note 3 25 40 – dB
Channel Balance (Monaural) VIN = 180mV – 0.3 3.0 dB

in

– 50k – Ω

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)

Distortion (75µs De–emphasis)

nd

Harmonic

2

3rd, 4th, and 5th Harmonic – < 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

19kHz pilot–tone voltage = 18mV ±6.6 ±10 – %

VIN = 240mV – 0.2 – %

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) in-

cluding a 19kHz (18mV) pilot–tone signal.