TDA7541 STMicroelectronics, TDA7541 Datasheet - Page 34

• Manufacturer Part Number: TDA7541
• Description: IC TUNER AM/FM CAR RADIO 64-LQFP
• Manufacturer: STMicroelectronics

Specifications of TDA7541

• Modulation Or Protocol: AM, FM
• Applications: Automotive Audio
• Current - Receiving: 48mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 7.7 V ~ 9 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Frequency: -
• Sensitivity: -
• Memory Size: -
• Data Rate - Maximum: -
• Lead Free Status / Rohs Status: Compliant

Functional description
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frequency of 140 kHz. The rectified signal, VRECT, is low pass filtered to generate a signal
called V
resulting voltage can be adjusted by use of the noise rectifier discharge current. The V
voltage is fed to a threshold generator, which adds to the V
VTH. Both signals, V
triggerable monoflop. The output of the monoflop activates the sample-and-hold circuit in
the signal path for the selected duration.
Automatic noise controlled threshold adjustment
There are mainly two independent possibilities for programming the trigger threshold:
1.
2.
The low threshold is active in combination with a good MPX signal without any noise; the
V
If the MPX signal is noisy (low field strength) the V
noise, which is also rectified. With increasing of the V
increases, too. This particular gain is programmable in 4 steps (NBCT).
Figure 5.
Automatic stereo blend controlled threshold adjustment
Besides the noise controlled threshold adjustment there is an additional possibility for
influencing the noise blanker trigger threshold using the bits NBFC. This influence depends
on the stereo blend control. The point where the MPX signal starts to become noisy is fixed
by the RF part. This point is also the starting point of the normal noise-controlled trigger
adjustment. But in some cases the noise blanker can create a wrong triggering, which
create distortion, already in the region of mono/stereo transition. Therefore an opportunity to
control the V
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Low threshold in 8 steps (NBLT)
Noise adjusted threshold in 4 steps (NBCT).
voltage is less than 1V. The sensitivity in this operation is high.
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. Noise with a frequency above 140 kHz increases the V
Adaptive threshold control of noise blanker
8 STEPS
voltage by the stereo blend function it is implemented.
200 mV
147 mV
RECT
VTH
Min. Trig. Threshold
and V
0.8 V
Doc ID 13686 Rev 4
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+VTH are fed to a comparator, which triggers a re-
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1.5 V
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Noise Controlled Trig. Threshold
voltage increases due to the higher
voltage the trigger threshold
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voltage a DC threshold
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1200 mV (00)
950 mV (01)
700 mV (10)
450 mV (11)
V
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voltage. The
TDA7541
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