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U4275B PDF 데이터시트 : 부품 기능 및 핀배열

부품번호 U4275B
기능 FM-Receiving Condition Analyser and Multipath Noise Cancellation
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U4275B 데이터시트, 핀배열, 회로
TELEFUNKEN Semiconductors
U4275B
FM-Receiving Condition Analyser and Multipath Noise
Cancellation
Description
The U4275B is a bipolar integrated receiving conditions
analyser as well as multipath noise cancellation circuit.
It is designed for high performance car radio applications.
Features
D Preparation of the fieldstrength signal
D Detection of multipath and common channel
interferences
D Evaluation of the receiving conditions by
microcomputer
D Interrupt output for abruptly occuring interferences
D Suitable for analogue as well as digital processing
D Mute function controllable by microcomputer
D Multipath noise cancellation
D Only a few external components necessary
Block diagram
14
CRIN
Oscillator
FIL19 FIL26 CCHFIL
20 19 17
Common
channel
detector
Filter
FSIN
AVFS
1
3
Multipath
detector
Interference
interrupt
9
INT
Reset
Analogue
multiplex
Address
logic
12
ADDR0
13
ADDR1
15 OE
11
ANAOUT
2
BFSOUT
Buffer
94 8644
MNC
control
10 18
MUTE MPFIL
Multipath
Noise
Cancellation
(Gain 1.5)
7
Bandgap VS
4 568
16
GND2 VREF GND1
MPXIN MPXOUT
Rev. A1: 14.03.1995
Preliminary Information
1




U4275B pdf, 반도체, 판매, 대치품
U4275B
INT
INT
+5V
25 kW
TELEFUNKEN Semiconductors
The controller element detects the absolute value of
occuring multipath interference. This information is
stored in a capacitor which must be connected externally
to MPFIL. The capacitor voltage can be interrogated by
the system controller via ANAOUT.
FIL19 / FIL26
94 8654
Certain types of abruptly occuring interference with
reception require a fast reaction by the receiver. INT
msignals such events to other circuit parts by means of
40- s-wide pulses (low active). The output voltage is
limited to 5 V to permit direct activation of a system
controller. A monoblend function can thus be activated on
simple receivers. On antenna-diversity receivers, INT
can activate switchover between antennas.
WFIL19 100 k
100 nA
94 8657
CCFIL
WCCFIL 100 k
WFIL26 100 k
100 nA
100 nA
94 8655
The controller element detects the absolute value of
occuring common channel interference. This information
is stored in a capacitor which must be connected
externally to CGFIL. The capacitor voltage can be
selected by the system controller and then available via
ANAOUT.
MPFIL
94 8658
In order to differentiate the various types of interference,
the amplitudes of a few spectral components of the
fieldstrength signal are determined and filtered in FIL19
and FIL26 for further processing.
VREF
VS
VREF
30 k
WMPFIL 100 k
94 8656
100 nA
30 k
94 9669
IF Mute is activated, the reference voltage VREF will
apply to the output MPXOUT. A capacitor of 100 nF
should be connected at VREF for filtering.
4
Preliminary Information
Rev. A1: 14.03.1995

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U4275B 전자부품, 판매, 대치품
TELEFUNKEN Semiconductors
U4275B
Multipath detector
Typical multipath interference is characterized by fast,
modulation-dependent field strength dips, as shown in
figure 2. The multipath detector detects these field
strength dips and evaluates them in accordance with the
level of anticipated acoustic interference.
In the case of acoustically relevant interference, it
operates the interrupt output INT and the MNC function
as a reaction to the interference. If the acoustic effects of
interference can be reduced by monoblend, only pulses
will appear at output INT. In the case of stronger
interference, interference suppression takes place by
means of the Multipath Noise Cancellation (MNC)
function. The multipath interference also generates a
voltage proportional to the interference level at MPFIL.
The capacitor connected there is responsible for storing
the information to give the system controller sufficient
time to read out the value at ANAOUT. The capacitor at
MPFIL is discharged again slowly with a long time
constant. The corresponding addressing at ADDR0,
ADDR1 and OE to permit a rapid assessment when the
station is changed.
Multipath Noise Cancellation (MNC)
Extremely strong multipath interference remains audible
in spite of the monoblend function. The remaining
interference is reduced still further by the MNC circuit if
the output MPXOUT is connected to a reference voltage
for a few microseconds while the interference is still
occuring.
In order to eliminate the possibility of malfunctions,
activation of the MNC depends on the following
conditions:
– The average field strength must exceed a certain
value so that the noise in the field strength
signal does not cause the MNC to respond at low
RF voltages and
– the field strength dip must not be caused by
adjacent-channel interference. Blanking will
otherwise make the modulation of the adjacent
channel audibly. The information for this
purpose is derived from the common channel
detector.
The MNC function can also be activated externally via
the MUTE pin (low active). The circuit can therefore also
be used as a fast high performance mute stage.
Common channel detector
The common channel detector evaluates the spectral
composition of the field strength signal to distinguish
common channel interference from other types of
interference. This is a particularly difficult task, since
weak multipath interference results in a spectrum of the
field strength signal that is similar to that of common
channel interference. the pilot signal portion of the field
strength signal serves as a reference variable to permit a
clear distinction to be made. A voltage proportional to the
interference is generated at the filter input CCFIL in the
case of common channel interference. The external
capacitor is responsible for storing the information to give
the system controller sufficient time to read out the value
at ANAOUT. The capacitor is discharged again slowly at
CCFIL, with a long time constant. The capacitor can also
be discharged rapidly via corresponding addressment
when stations are changed.
The common channel detector is blocked for further
20 ms after the detectors are reset to prevent transitory
phenomena in the selective filters from causing an
indicating error.
Rev. A1: 14.03.1995
Preliminary Information
7

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부품번호상세설명 및 기능제조사
U4275B

FM-Receiving Condition Analyser and Multipath Noise Cancellation

TEMIC Semiconductors
TEMIC Semiconductors

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