Features
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FM Double-conversion System
Integrated Second IF Filter with Software-controlled Bandwidth
Completely Integrated FM Demodulator
Soft Mute and Multipath Noise Cancellation
Receiving Condition Analyzer
AM Up/Down-conversion System
AM Preamplifier with AGC and Stereo Capability
3-wire Bus Controlled
Search Stop Signal Generation (AM and FM)
Automatic Alignment Possible
Pin Compatible with U4255BM
World Tuner, US Weatherboard, J-band
AM/FM
Receiver IC
T4258N
Electrostatic sensitive device.
Observe precautions for handling.
Description
The T4258N is a highly integrated AM/FM front-end circuit manufactured using
Atmel’s advanced BICMOS technology. It represents a complete, automatically adjust-
able AM/FM front end, containing a double-conversion system for FM and an
up/down-conversion receiver for AM with IF1 = 10.7 MHz and IF2 = 450 kHz. The
front end is suitable for digital or analog AF-signal processing. Together with the PLL
U4256BM, an automatically aligned high-performance AM/FM tuner can be built.
These ICs are dedicated for highly sophisticated car radio applications.
Rev. 4566B–AUDR–02/04
Figure 1.
Block Diagram
IF1FMI
MX1OA
43
MX1OB
44
IF1REF
38
39
33
AM
AM
Dem.
FM
41
MX1AMA
MX1AMB
AMAGC
AMVREG
AMPLPF
3
7
6
8
AGC
V3
Noise-
blanker
AGC
MX1FMA
MX1FMB
2
GNDMX
OSCOUT
16
Divider
GNDOSC
OSCE
OSCB
4
Divider
2...10
Offset
Adj.
Chan.
Stop
FM
Dem.
Soft
Mute
MPX
11
1
35
20
Automatic
FILADJ
Adjustment 37
AM
AGC
IFAGCL
IFAGCH
IF2OUT
OPLPF
32
IF1AMI
V3
MX2OB
IF1OUT MX2IN
30
29
26
23
MX2OA
24
IF2IN V3P
28
27
36
FM
Multi-
MULTIP
path 40
15
14
13
OSC
V3
Bandgap
12
25 42
5
Bus
17 18
19
9
METER
22
MX2LO
10
ADJAC
INT
21
INT
34
SMUTE
Dev.
Ana.
31
DEV
V57
VS
EN
DATA
GND
FMAGC
CLK
2
T4258N
4566B–AUDR–02/04
T4258N
Pin Configuration
Figure 2.
Pinning SSO44
MX1FMA
MX1FMB
MX1AMB
GNDMX
FMAGC
AMVREG
AMAGC
AMPLPF
METER
1
2
3
4
5
6
7
8
9
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
MX1OB
MX1OA
VS
MX1AMA
MULTIP
IF1REF
IF1FMI
FILADJ
IFAGCL
IFAGCH
SMUTE
IF1AMI
OPLPF
DEV
IF1OUT
V3
IF2IN
V3P
MX2IN
GND
MX2OA
MX2OB
ADJAC 10
MPX 11
V57 12
OSCB 13
OSCE 14
GNDOSC 15
OSCOUT 16
EN 17
CLK 18
DATA 19
IF2OUT 20
INT 21
MX2LO 22
3
4566B–AUDR–02/04
Pin Description
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Symbol
MX1FMA
MX1FMB
MX1AMB
GNDMX
FMAGC
AMVREG
AMAGC
AMPLPF
METER
ADJAC
MPX
V57
OSCB
OSCE
GNDOSC
OSCOUT
EN
CLK
DATA
IF2OUT
INT
MX2LO
MX2OB
MX2OA
GND
MX2IN
V3P
IF2IN
V3
IF1OUT
DEV
OPLPF
IF1AMI
SMUTE
IFAGCH
IFAGCL
FILADJ
IF1FMI
IF1REF
MULTIP
Function
1
st
mixer FM input A
1
st
mixer FM input B
1
st
mixer AM input B
Ground 1
st
mixer, preamplifier AGC
FM preamplifier AGC
AM control voltage
AM preamplifier AGC
AM AGC LP filter
Field strength output
Adjacent channel detection output
Multiplex signal
5.7 V reference voltage
Oscillator basis
Oscillator emitter
Oscillator ground
Oscillator output
3-wire bus enable
3-wire bus clock
3-wire bus data
2
nd
IF amplifier output
Interrupt, stop signal
10.25 MHz input for 2
nd
mixer
2
nd
mixer output B
2
nd
mixer output A
Ground
2
nd
mixer input
3 V reference for AMPIN, AMIFAGC, Control, IF2IN
2
nd
IF amplifier input
3 V reference for IF1OUT, MX2IN
1
st
IF amplifier output
Deviation detect output, test output
Operating point LPF
1
st
IF AM amplifier input
Soft MUTE control input
IF AGC LP filter high time
IF AGC LP filter low time constant
Filter adjust
1
st
IF FM amplifier input
1
st
IF & MX1OUT reference, MX1AM A, MX1AM B
Multipath detection output
4
T4258N
4566B–AUDR–02/04
T4258N
Pin Description (Continued)
Pin
41
42
43
44
Symbol
MX1AMA
VS
MX1OA
MX1OB
Function
1
st
mixer AM input A
Supply voltage
1
st
mixer output A
1
st
mixer output B
Functional
Description
The T4258N implements an AM up/down-conversion reception path from the RF input
signal to the AM-demodulated audio frequency output signal, and for FM/WB reception
a double-conversion reception path from the RF input signal to the FM-demodulated
multiplex signal (MPX). A VCO and an LO prescaler for AM are integrated to generate
the LO frequency for the 1
st
mixer. Automatic gain control (AGC) circuits are imple-
mented to control the preamplifier and IF stages in the AM and FM reception path.
For improved FM performance, an integrated IF filter with adjustable bandwidth, a soft-
mute feature and an automatic multipath noise cancellation (MNC) circuit are fully
integrated. A powerful set of sensors is provided for receiving condition analysis and
stop signal generation.
Several register bits (bit 0 to bit 93) are used to control circuit operation and to adapt
certain circuit parameters to the specific application. The control bits are organized in
two 8-bit and three 24-bit registers that can be programmed by the 3-wire bus protocol.
The bus protocol and the bit-to-register mapping is described in the section “3-wire Bus
Description” on page 20. The meaning of the control bits is mentioned in the following
sections.
The integrated VCO has a high frequency range. Additionally the VCO has a special
VCO divider which allows (in connection with the VCO) the reception of all analog world
bands.
Reception Mode
The IC can be operated in four different modes. Mode AM, FM, WB, and Standby are
selected by means of bit 92 and bit 93 according to Table 1 on page 6.
Additionally to the operating modes, the signal paths can be set separately. Bit 62
selects the first mixer and AGC, bit 63 selects the 1
st
amplifier stage. The recommended
settings of bit 62 and bit 63 are included in Table 1 on page 6.
In AM mode the AM mixer, the AM RF-AGC and the 1
st
IF AM amplifier at pin 33 are
activated. The input of the 2
nd
IF amplifier is connected to pin 28 and the output of the
2
nd
IF amplifier is fed to the AM demodulator. The output of the AM demodulator is
available at MPX output pin 11.
In FM mode the FM mixer, the FM RF-AGC and the 1
st
IF FM amplifier at pin 38 are acti-
vated. The bandwidth of the output tank at pin 23, pin 24 is increased and the input of
the 2
nd
IF amplifier can be switched between pin 23 and pin 24 and pin 28. The output of
the 2
nd
IF amplifier is fed to the integrated band filter and FM demodulator. The output of
the FM demodulator is available at MPX output pin 11.
The WB mode is similar to the FM mode, but to reduce the bandwidth the AM IF ampli-
fier with the AM filter (bit 63 = 1) can be used. In WB mode the range of the integrated
filter bandwidth control is shifted to lower bandwidth and the gain of the FM demodulator
is increased.
In standby mode the mixers, IF amplifiers and AGC circuits are deactivated to reduce
current consumption.
5
4566B–AUDR–02/04
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