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Электронный компонент: U4275B-MFL

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Features
Preparation of the fieldstrength signal
Detection of multipath and common channel interferences
Evaluation of the receiving conditions by microcomputer
Interrupt output for abruptly occuring interferences
Suitable for analog as well as digital processing
Mute function controllable by microcomputer
Multipath noise cancellation
Only few external components necessary
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.
Block Diagram
Figure 1.
Multipath
detector
Common
channel
detector
Interference
interrupt
Oscillator
Filter
Reset
Analogue
multiplex
Address
logic
MNC
control
Buffer
Bandgap
14
1
3
2
20
17
19
9
12
13
15
11
7
10
18
4
5
6
16
FIL19
FIL26
CCHFIL
ADDR0
ADDR1
INT
OE
ANAOUT
V
S
MUTE
MPXIN
GND2
MPXOUT
GND1
MPFIL
CRIN
BFSOUT
AVFS
FSIN
Multipath
Noise
Cancellation
(Gain 1.5)
8
VREF
Ordering Information
Extended Type Number
Package
Remarks
U4275B-MFL
SO20 plastic
U4275B-MFLG3
SO20 plastic
Taped and reeled
FM Receiving
Condition
Analyzer and
Multipath Noise
Cancellation IC
U4275B
Rev. A3, 16-Oct-01
2 (14)
U4275B
Rev. A3, 16-Oct-01
Pin Configuration
Figure 2. Pinning SO20
1
2
3
4
5
6
7
8
10
9
19
18
17
16
14
15
13
12
11
20
FSIN
BFSOUT
AVFS
MPXIN
GND2
MPXOUT
VS
VREF
INT
MUTE
ANAOUT
ADDR0
ADDR1
CRIN
OE
GND1
CCFIL
MPFIL
FIL26
FIL19
Pin Description
Pin
Symbol
Function
1
FSIN
Fieldstrength input
2
BFSOUT
Buffered fieldstrength output
3
AVFS
Average of fieldstrength signal
4
MPXIN
Multiplex input signal
5
GND2
Analog ground
6
MPXOUT
Multiplex output signal
7
VS
Supply voltage
8
VREF
Reference voltage
9
INT
Interrupt output
10
MUTE
External mute input
11
ANAOUT
Analog multiplex output
12
ADDR0
Address 0 for analog multiplexer
13
ADDR1
Address 1 for analog multiplexer
14
CRIN
Ceramic resonator input (456 kHz)
15
OE
Output enable for ANAOUT
16
GND1
Ground
17
CCFIL
Filter for common channel detection
18
MPFIL
Filter for multipath detection
19
FIL26
Filter for 26-kHz detection
20
FIL19
Filter for 19-kHz-Pilot detection
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U4275B
Rev. A3, 16-Oct-01
FSIN / BFSOUT
All information about reception conditions is derived from the fieldstrength voltage. The
fieldstrength voltage at FSIN is initially buffered so as not to impair the characteristics of
the IF IC and is available at BFSOUT.
AVFS
The fieldstrength signal at buffer output BFSOUT is averaged over time and applied to
input AVFS via an RC low-pass filter with a large time constant.
MPXIN / MPXOUT
The MPX signal is fed directly from the FM demodulator to input MPXIN and is available
amplified by a factor of 1.5 at MPXOUT. The MPX signal is blanked out in the event of
multipath interference or when MUTE is activated externally in the circuit part MNC
(Multipath Noise Canceller). In all other cases, the MPX signal passes through the IC
unchanged.
FSIN
40 A
V
S
BFSOUT
AVFS
40 A
V
S
50 k
MPXIN
50 k
V
S
60 k
60 k
MPXOUT
200 A
V
S
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U4275B
Rev. A3, 16-Oct-01
GND2
GND2 is the reference potential for the MPX signal. GND2 should be connected directly
with the ground terminal of the IF FM demodulator to ensure a high signaltonoise ratio
of the MPX signal.
MUTE
The function unit MNC can be controlled externally via this pin. Blanking occurs when
the voltage at the MUTE pin falls below 1 V. A voltage in the range VS/2 > 1 V defines
the switching threshold as from which multipath interference is signalled at pin INT.
CRIN
The internal one-pin oscillator is connected to CRIN with a 456-kHz ceramic resonator.
The 456-kHz reference frequency is used for calibrating the filters and generating
pulses at INT.
ANAOUT
Analyzer output. DC values are available at this pin that characterize the respective
reception situation. The output voltage is limited to max. 5 V. ANAOUT is a multiplex
output, i.e. the value for the fieldstrength, level of multipath interference or level of com-
mon channel interference is applied to this output depending on addressing. ANAOUT
can be switched to the high-impedance state by means of OE.
MUTE
CRIN
V
S
40 k
ANAOUT
60 A
+ 5 V
5 (14)
U4275B
Rev. A3, 16-Oct-01
INT
Certain types of abruptly occuring interferences with reception require a fast reaction by
the receiver. INT signals 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.
CCFIL
This controller element detects the absolute value of occuring common channel interfer-
ence. This information is stored in a capacitor which must be connected externally to
CGFIL. The capacitor voltage can be selected by the system controller which is then
available via ANAOUT.
MPFIL
This 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.
25 k
+ 5 V
INT
CCFIL
100 k
100 nA
MPFIL
100 k
100 nA