TDA7361D View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TDA7361D Datasheet PDF : 8 Pages
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TDA7361
Pin FUNCTION
No
Name
1-2
XTAL OSCILLATOR
3
MIXER OUT
4
SUPPLY VOLTAGE
5
IF LIMITER INPUT
6-7
DECOUPLING
8
QUADRATURE COIL
9
AUDIO OUTPUT SIGNAL
10
OPERATIONAL
AMPLIFIER INPUT
11
OPERATIONAL
AMPLIFIER OUTPUT
12
SQUELCH INPUT
13
SCAN CONTROL
14
MUTE
15
GND
16
10.7MHz MIXER INPUT
Function
Connections for the Colpitts XTAL Oscillator.
The XTAL may be replaced by an inductor (see Figure 5) if the application
does not require high stability.
The Mixer is double balanced to reduce spurious products. The output
impedance is 1.8kW to match the input impedance of a 455kHz ceramic filter.
Must be well decoupled with a 100nF ceramic capacitor.
Input pin of the six stages amplifier with about 50µV limiting sensitivity and
1.8kΩ input impedance. The if output is connected to the external quadrature
coil (Pin 8) via an internal 10pF capacitor.
Good quality 100nF ceramic capacitors and a suitable layou are important.
A quadrature detector is uded to demodulate the 455kHz FM signal. The Q of
the quad coil has direct effect on output level and distorsion (see Figure 6).
For proper operation the voltage should be 100mVRMS.
The audio output signal is buffered by an internal emitter follower.
Because of the low DC bias, the swing on the operational amplifier output is
limited to 500mVRMS.
This can be increased by adding a resistor from the operational amplifier input
to ground.
The squelch trigger circuit with a low bias on the input (Pin 12) will force Pin
13 high ; and Pin 14 low.
Pulling Pin 12 above mute threshold (0.65V) will force Pin 13 to an impedance
of about 60kΩ to ground and Pin 14 will be an open circuit.
An hysteresis of about 50mV at Pin 12 will effectively prevent jitter.
Ground Connection
Input of the Wide-band Mixer. Normally used as 10MHz/455kHz converter, it
can be also used with input frequencies up to 60MHz.
BLOCK DIAGRAM
2/8
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