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TEMIC Semiconductors |
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
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 Analogue 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 Analogue multiplex output
12 ADDR0 Address 0 for analogue multi-
plexer
13 ADDR1 Address 1 for analogue multi-
plexer
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
TELEFUNKEN Semiconductors
FSIN 1
BFSOUT 2
AVFS 3
MPXIN 4
GND2 5
MPXOUT 6
VS 7
VREF 8
INT 9
MUTE 10
20 FIL19
19 FIL26
18 MPFIL
17 CCFIL
16 GND1
15 OE
14 CRIN
13 ADDR1
12 ADDR0
11 ANAOUT
94 8830
FSIN / BFSOUT
AVFS
VS
FSIN
40 mA
BFSOUT
AVFS
40 mA
94 8647
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.
94 8648
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.
2
Preliminary Information
Rev. A1: 14.03.1995
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