ATMEL U4255BM-M

Features
•
•
•
•
•
•
•
•
•
•
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 for AM and FM
Automatic Alignment Possible
AM/FM
Receiver IC
Electrostatic sensitive device.
Observe precautions for handling.
U4255BM-M
Description
The U4255BM-M is a highly integrated AM/FM front-end circuit manufactured using
Atmel’s advanced BICMOS technology. It represents a complete, automatically adjustable 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.
Preliminary
Pin Configuration
V3P
MX2IN
27
26
25
24
23
CLK 18
DATA 19
IF2OUT 20
INT 21
MX2LO 22
MX2OB
IF2IN
28
EN 17
MX2OA
V3
29
OSCOUT 16
GND
30 IF1OUT
GNDOSC 15
31 DEV
OSCE 14
OPLPF
32
OSCB 13
IF1AMI
33
V57 12
IFAGCH
34
MPX 11
SMUTE
35
ADJAC 10
IFAGCL
36
9
METER
FILADJ
37
8
AMPLPF
IF1FMI
38
7
AMAGC
IF1REF
39
6
MULTIP
AMVREG
40
5
FMAGC
MX1AMA
41
4
GNDMX
42
VS
3
MX1AMB
MX1OA
43
2
MX1FMB
44
1
MX1FMA
MX1OB
Figure 1. Pinning SSO44
Rev. 4519C–AUDR–07/02
1
Pin Description
2
Pin
1
Symbol
MX1FMA
Function
1st mixer FM input A
2
3
MX1FMB
MX1AMB
1st mixer FM input B
1st mixer AM input B
4
5
GNDMX
FMAGC
Ground 1st mixer, preamplifier AGC
FM preamplifier AGC
6
7
AMVREG
AMAGC
AM control voltage
AM preamplifier AGC
8
9
AMPLPF
METER
AM AGC LP filter
Field strength output
10
11
ADJAC
MPX
Adjacent channel detection output
Multiplex signal
12
13
V57
OSCB
5.7 V reference voltage
Oscillator basis
14
15
OSCE
GNDOSC
Oscillator emitter
Oscillator ground
16
17
OSCOUT
EN
Oscillator output
3-wire bus enable
18
19
CLK
DATA
20
21
IF2OUT
INT
2nd IF amplifier output
Interrupt, stop signal
22
23
MX2LO
MX2OB
10.25 MHz input for 2nd mixer
2nd mixer output B
24
25
MX2OA
GND
2nd mixer output A
Ground
26
27
MX2IN
V3P
2nd mixer input
3 V reference for AMPIN, AMIFAGC, Control, IF2IN
28
29
IF2IN
V3
30
31
IF1OUT
DEV
1st IF amplifier output
Deviation detect output, test output
32
33
OPLPF
IF1AMI
Operating point LPF
1st IF AM amplifier input
34
35
SMUTE
IFAGCH
Soft MUTE control input
IF AGC LP filter high time
36
37
IFAGCL
FILADJ
IF AGC LP filter low time constant
Filter adjust
38
39
IF1FMI
IF1REF
1st IF FM amplifier input
1st IF & MX1OUT reference, MX1AM A, MX1AM B
40
41
MULTIP
MX1AMA
42
43
VS
MX1OA
Supply voltage
1st mixer output A
44
MX1OB
1st mixer output B
3-wire bus clock
3-wire bus data
2nd IF amplifier input
3 V reference for IF1OUT, MX2IN
Multipath detection output
1st mixer AM input A
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Figure 2. Block Diagram
MX1OA
IF1FMI
MX2OB
IF1AMI
V3
MX1OB
IF1REF
IF1OUT MX2IN
MX2OA
AMPLPF
43
8
7
AMAGC
6
AMVREG
44
38
39
33
30 29
26
23
24
IF2IN
28
V3P
IF2OUT
27
20
AM
AGC
FM
AM
dem.
MX1AMA
MX1AMB
41
32
AM
3
V3
AGC
36
35
GNDMX
MX1FMB
MX1FMA
OSCOUT
OPLPF
IFAGCL
IFAGCCH
4
2
FM
Automatic
adjustment
AGC
1
16
37
FILADJ
Multipath
Divider
11
GNDOSC
OSCE
OSCB
Adj.
chan
.
15
14
FM
dem.
Stop
Soft
mute
MPX
OSC
13
V3
Bus
17 18 19
Bandgap
5
12 25 42
GND
EN
DATA FMAGC
V57
VS
CLK
Functional
Description
Dev.
ana.
INT
9
METER
22
MX2LO
10
ADJAC
21
INT
40
MULTIP
34
31
SMUTE
DEV
The U4255BM-M implements an AM up/down-conversion reception path from the RF
input signal to the AM-demodulated audio frequency output signal, and for FM 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 1st mixer. Automatic gain control (AGC) circuits are implemented 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 softmute 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’. The meaning of the control bits is mentioned in the following sections.
Reception Mode
The IC can be operated in four different modes. Mode AM, FM, WB, Standby are
selected by means of Bit 92 and Bit 93 according to Table 1.
In AM mode the AM mixer, the AM RF-AGC and the 1st IF AM amplifier at Pin 33 are
activated. The input of the 2nd IF amplifier is connected to Pin 28 and the output of the
2nd IF amplifier is fed to the AM demodulator. The output of the AM demodulator is
available at MPX output Pin 11.
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4519C–AUDR–07/02
In FM mode the FM mixer, the FM RF-AGC and the 1st IF FM amplifier at Pin 38 are
activated. The bandwidth of the output tank at Pin 23, Pin 24 is increased and the input
of the 2nd IF amplifier can be switched between Pin 23, Pin 24 and Pin 28. The output of
the 2nd IF amplifier is fed to the integrated bandfilter and FM demodulator. The output of
the FM demodulator is available at MPX output Pin 11.
WB mode is similar to FM mode but the input of the 2nd IF amplifier is fixed to Pin 28, the
range of the bandwidth control of the integrated band filter 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.
Table 1. Operating Mode
Test Mode
AM/FM/Weather Channel
Standby
Bit 93
0
Bit 92
0
FM
AM
0
1
1
0
Weather band
1
1
A special test mode is implemented for final production test only. This mode is activated
by setting Bit 9 = 1. This mode is not intended to be used in customer application.
For normal operation, Bit 9 has to be set to 0. Bit 18 to Bit 30 are deactivated in normal
operation mode.
Table 2. Test Mode
Mode
Normal operation
Bit 9
0
Testmode
1
VCO
An oscillator circuit is implemented to build a VCO as proposed in the application schematic. The VCO frequency is used to generate the LO frequency of the 1st mixer stages.
The control voltage of the VCO is usually generated by the PLL circuit U4256BM. The
VCO signal is provided at the buffered output Pin 16 to be fed to the PLL circuit.
FM RF-AGC
The FM RF-AGC circuit includes a wideband level detector at the input Pin 1 of the FM
mixer and an in-band level detector at the output of the FM IF amplifier (Pin 30). The
outputs of these level detectors are used to control the current into the pin diode (see
Figure 3) in order to limit the signal level at the FM mixer input and the following stages.
The maximum pin diode current is determined by R115 and the time constant of the
AGC control loop can be adjusted by changing the value of C111.
The AGC threshold level at the input of the FM mixer can be adjusted by Bit 64 and
Bit 65 according to Table 3. The in-band AGC threshold referred to the FM mixer input
(Pin 1, Pin 2) depends on the gain of the FM IF amplifier and can be adjusted by Bit 89
to Bit 91.
4
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Table 3. FM-AGC Threshold
FM-AGC Threshold
104 dBmV
Bit 65
0
Bit 64
0
101 dBmV
98 dBmV
0
1
1
0
92 dBmV
1
1
Figure 3. FM RF-AGC Bit 92
VS
Pin 42
C111
R115
Pin 5
PIN Diode
AGC
AM RF-AGC
B92
The AM RF-AGC controls the current into the AM pin diodes (Pin 7) and the source
drain voltage of the MOSFET in the AM preamplifier stage (Pin 6) to limit the level at the
AM mixer input (Pin 3, Pin 41). This threshold level can be set by Bit 62 and Bit 63. If the
level at the AM mixer input exceeds the selected threshold, the current into the AM pin
diodes is increased. If this step is not sufficient, the source drain voltage of the MOSFET
is decreased. The time constant of the AGC control loop can be adjusted by changing
the value of the capacitor at Pin 8.
Table 4. AM-AGC Threshold
AM-AGC Threshold
99 dBmV
Bit 63
0
Bit 62
0
102 dBmV
104 dBmV
0
1
1
0
105 dBmV
1
1
FM 1st Mixer
In the 1st FM mixer stage, the FM reception frequency is down converted to the 1st IF
frequency. The VCO frequency is used as LO frequency for the mixer.
AM 1st Mixer
The AM 1st mixer is used for up-conversion of the AM reception frequency to the 1st IF
frequency. Therefore, an AM prescaler is implemented to generate the necessary LO
frequency from the VCO frequency. The divide factor of the AM prescaler can be
selected according to Table 5.
5
4519C–AUDR–07/02
Table 5. Divide Factor of the AM Prescaler
FM 1st IF Amplifier
Divider AM Prescaler
Divide by 10
Bit 93
1
Bit 92
0
Bit 84
x
Bit 83
0
Bit 82
0
Bit 81
0
Divide by 6
Divide by 7
1
1
0
0
x
x
0
0
0
1
1
0
Divide by 8
Divide by 4
1
1
0
0
x
x
1
1
0
0
0
1
A programmable gain amplifier is used in FM and WB mode between Pin 38 and Pin 30
to compensate the loss in the external ceramic band filters. The gain of this amplifier is
adjusted by Bit 89 to Bit 91. The input and the output resistance is 330 W and fits to
external ceramic filters.
Two different temperature coefficients of the FM IF amplifier can be selected by Bit 66.
Table 6. Gain of the FM IF Amplifier
Gain FM IF
Bit 91
Bit 90
Bit 89
20 dB
22 dB
0
0
0
0
0
1
24 dB
26 dB
0
0
1
1
0
1
28 dB
29 dB
1
1
0
0
0
1
30 dB
31 dB
1
1
1
1
0
1
Table 7. Temperature Coefficient Setting of FM IF Amplifier
Temperature Coefficient (TC) of the IF Amplifier
TKmin
Bit 66
0
TKmax
1
AM 1st IF Amplifier
In AM mode, the gain of the 1st IF amplifier is controlled by the IF-AGC to extend the
control range of the IF-AGC.
2nd Mixer
The 2nd mixer is used in AM, FM and WB mode. The mixer input has 330 W input resistance and can be connected directly to an external ceramic filter.
In FM mode, the high output resistance of the second mixer is reduced to increase the
bandwidth of the tank at the mixer output. The output resistance can be selected by
Bit 60 and Bit 61.
Table 8. 2nd Mixer Output Resistance in FM Mode
Bit 61
0
Bit 60
0
Output Resistance (Bit 54 = 0)
3.3 kW
Output Resistance (Bit 54 = 1)
~ 100 kW
0
1
1
0
0.63 kW
0.47 kW
0.78 kW
0.55 kW
1
1
0.29 kW
0.32 kW
The LO frequency of the 2nd mixer (10.25 MHz) has to be applied at Pin 22. This signal
is usually generated by the PLL circuit U4256BM.
6
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Table 9. FM Bandwidth Mixer 2
Bit 61
0
Bit 60
0
FM BW Mixer 2
150 kHz
0
1
1
0
200 kHz
250 kHz
1
1
450 kHz
Remark: The bandwidth is also depending from the values of the application circuit.
2nd IF Amplifier
In AM and WB mode, the input of the second IF amplifier is Pin 28, which is externally
connected to the 2nd mixer tank through the AM ceramic filter to achieve channel selectivity. During normal FM operation (Bit 54 = 0), the input of the second IF amplifier is
connected to the 2nd mixer output (Pin 23, Pin 24) and the integrated FM band filter is
used for channel selectivity only. It is possible to use an additional external filter
between the 2nd mixer tank and Pin 28 in FM mode by setting Bit 54 to 1.
Table 10. 2nd IF Filter in FM Mode
IF-AGC
2nd IF Filter
Internal filter
Bit 54
0
External and internal filter
1
The IF-AGC controls the level of the 2nd IF signal that is passed to the AM demodulator
input or the integrated FM bandfilter and to the 2nd IF output Pin 20.
Two different time constants of the IF-AGC can be selected by the capacitors at Pin 35
(IFAGCH) and Pin 36 (IFAGCL). The short time constant (IFAGCL) is used in FM mode
and in AM search mode. The long time constant (IFAGCH) is used for AM reception.
Table 11. IF-AGC Time Constant
Mode
Bit 92
Bit 88
IF AGC Time Constant
FM/WB
AM reception
1
0
X
0
IFAGCL (fast)
IFAGCH (slow)
AM search
0
1
IFAGCL (fast)
In FM/WB mode, the output signal of the FM demodulator is applied to Pin 35 via a
series resistor of about 95 kW. This low-pass filtered output signal of the FM demodulator is used for the FM demodulator fine adjustment, for muting and as a reference for the
deviation sensor.
2nd IF Output
The 2nd IF after the gain-controlled 2nd IF amplifier is available at Pin20 (Bit 55 = 0). In
AM mode, this signal may be used for an external AM stereo decoder. Alternatively, a
signal corresponding to the logarithmic field strength after the integrated FM band filter,
which is used for multipath detection, can be switched to Pin 20 by setting Bit 55 = 1.
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4519C–AUDR–07/02
Table 12. Pin 20 Output Setting
Pin 20
2 IF output
Bit 55
0
Multipath field strength
1
nd
Automatic IF Center
Frequency Adjustment
Integrated active filters are used in the FM band filter, FM demodulator and adjacent
channel sensor. The center frequency of these filters is automatically adjusted to the
second IF frequency of 450 kHz. The frequency of 10.25 MHz at Pin 22 is used as a
reference for this alignment.
Figure 4. Automatic IF Center Frequency Adjustment
Pin 22
10.25MHz
Automatic
Frequency
adjustment
center
freq.
center
freq.
Bit 14...17
+
Bit 56...59
Pin 37
+
center
freq.
FM-Demod
FMbandfilter
adj.channel
Sensor
Bit 5,6
For fine tuning, the center frequency of all these integrated active filters (band filter,
demodulator and adjacent channel sensor) can be shifted in steps of 6.25 kHz by
means of Bit 56 to Bit 59. Additionally, the center frequency of the band filter can be
adjusted separately by means of Bit 14 to Bit 17 if Bit 4 is set to 1. If Bit 4 is set to 0, the
default setting is used.
Table 13. 2nd IF Center Frequency
8
IF Center
450.00 kHz
Bit 59
0
Bit 58
0
Bit 57
0
Bit 56
0
456.25 kHz
461.50 kHz
0
0
0
0
0
1
1
0
468.75 kHz
475.00 kHz
0
0
0
1
1
0
1
0
481.25 kHz
487.50 kHz
0
0
1
1
0
1
1
0
493.75 kHz
450.00 kHz
0
1
1
0
1
0
1
0
443.75 kHz
437.50 kHz
1
1
0
0
0
1
1
0
431.25 kHz
425.00 kHz
1
1
0
1
1
0
1
0
418.75 kHz
412.50 kHz
1
1
1
1
0
1
1
0
406.25 kHz
1
1
1
1
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Table 14. FM Band Filter Center Frequency Correction
IF Correction
- 0 kHz
Bit 17
0
Bit 16
0
Bit 15
0
Bit 14
0
- 6.25 kHz
- 12.50 kHz
0
0
0
0
0
1
1
0
- 18.75 kHz
- 25.00 kHz
0
0
0
1
1
0
1
0
- 31.25 kHz
- 37.50 kHz
0
0
1
1
0
1
1
0
- 43.75 kHz
+ 0 kHz (default)
0
1
1
0
1
0
1
0
+ 6.25 kHz
+ 12.50 kHz
1
1
0
0
0
1
1
0
+ 18.75 kHz
+ 25.00 kHz
1
1
0
1
1
0
1
0
+ 31.25 kHz
+ 37.50 kHz
1
1
1
1
0
1
1
0
+ 43.75 kHz
1
1
1
1
Integrated FM Band Filter For FM reception a band filter with variable bandwidth is integrated in front of the
demodulator to provide channel selectivity on the 2nd IF. The bandwidth of this filter can
be adjusted by Bit 0 to 3 (see Table 15) to be suitable for the present receiving condition. In WB mode, the bandwidth of the integrated filter is shifted to lower bandwidth
values, while the necessary channel selectivity is achieved by an external ceramic filter.
The center frequency of the integrated FM band filter can be adjusted by means of
Bit 14 to 17 (Bit 4 set to 1). The field strength after the integrated FM band filter that is
available at Pin 20 (Bit55 = 1) can be used for this purpose.
Table 15. Bandwidth of the Integrated FM Band Filter.
IF Bandwidth
200 kHz
Bit 3
0
Bit 2
0
Bit 1
0
Bit 0
0
190 kHz
180 kHz
0
0
0
0
0
1
1
0
170 kHz
160 kHz
0
0
0
1
1
0
1
0
150 kHz
140 kHz
0
0
1
1
0
1
1
0
130 kHz
120 kHz
0
1
1
0
1
0
1
0
110 kHz
1
0
0
1
100 kHz
90 kHz
1
1
0
0
1
1
0
1
80 kHz
70 kHz
1
1
1
1
0
0
0
1
60 kHz
50 kHz
1
1
1
1
1
1
0
1
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4519C–AUDR–07/02
FM Demodulator
For weather band reception, the gain of the FM demodulator is increased and can be
adjusted by means of Bit 71, Bit 72 in order to increase the output voltage to compensate the low frequency deviation in weather band.
An integrated demodulator fine adjustment allows automatic fine tuning of the demodulator center frequency to the average frequency of the received signal. This feature is
implemented for use in weather band mode and can be activated by setting Bit 53 to 0.
Figure 5. FM Demodulator Automatic Fine Tuning
FM Demod
MPX
AM
AGC
center freq.
B92
+
IFAGCH
V3
(10nF)
Bit 53
Automatic
Frequency
adjustment
The center frequency of the FM demodulator can be adjusted by means of Bit 56 to 59.
At the center frequency, the DC voltage at the MPX output Pin 11 is equal to the MPX
offset voltage that can be measured at Pin 11 while MPX mute is active (Bit 7 = 1). This
adjustment will affect the center frequency of all integrated filters as mentioned before.
Table 16. Demodulator Gain in Weather Band Mode
Demodulator Gain in Weather Band Mode Relative to FM Mode
Bit 72
Bit 71
12 dB
15 dB
0
0
0
1
18 dB
21 dB
1
1
0
1
Table 17. Demodulator Fine Adjustment
10
Demodulator Fine Adjustment
Fine tuning ON
Bit 53
0
Fine tuning OFF
1
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Soft Mute
The soft mute functionality is implemented to reduce the output level of the FM demodulator at low input signal levels to limit the noise at MPX output in this case. If the input
level falls below an adjustable threshold, continuously the output of the FM demodulator
is continuously muted with decreasing input level until a maximum mute value is
reached. The threshold for the start of soft mute and the maximum mute can be
adjusted. The signal level for 3 dB mute can be set by means of Bit 68 to 70 and the
maximum value for soft mute can be selected by Bit 67. The steepness and the time
constant of the soft mute can be adjusted by the resistor and capacitor between Pin 34
and Pin 29.
The field strength signal available at Pin 9 is used for soft mute. Therefore, the soft mute
threshold referred to the input of the FM mixer depends on the gain from FM mixer input
to the field strength sensor.
Table 18. Soft Mute Threshold
Relative Soft Mute Threshold
Soft mute OFF
Bit 70
0
Bit 69
0
Bit 68
0
-18 dB
-15 dB
0
0
0
1
1
0
-12 dB
-9 dB
0
1
1
0
1
0
-6 dB
-3 dB
1
1
0
1
1
0
0 dB
1
1
1
Table 19. Maximum Soft Mute
Maximum Value of Soft Mute
28 dB
Bit 67
0
24 dB
1
Figure 6. Soft Mute
+
FS (Pin9)
Bit 67
Pin 34
Gain FM-Demodulator
Bit 68..70
Pin 29
V3
11
4519C–AUDR–07/02
MPX Output
The output of the AM demodulator (AM mode) or the output of the FM demodulator
(FM/WB mode) are available at the MPX output (Pin 11).
The MPX output signal can be muted by setting Bit 7 to 1.
The bandwidth of the lowpass filter at the MPX output can be set by means of Bit 79 to
90 kHz or 180 kHz.
Table 20. MPX Output Mute
MPX Output
MPX out, Pin 11 normal operation
Bit 7
0
Mute ON
1
Table 21. MPX Output Bandwidth
Bandwidth MPX Lowpass Filter
Bit 79
90 kHz
180 kHz
0
1
Receiving Condition
Analyzer
The U4255BM-M implements several sensors that provide information about the receiving condition of the selected station.
Field Strength Sensor
The field strength sensor provides a DC voltage at Pin 9 which represents the logarithmic field strength of the signal in the reception band.
The field strength information can be retrieved either from a level detector at the input of
the 2nd mixer (Pin 26) or from the IF-AGC depending on the setting of Bit 80. The bandwidth of the field strength detection in the AGC is smaller than by using the level
detector because of additional selectivity between the 2nd mixer and the 2nd IF amplifier
particularly in AM and WB, but the field strength detection in the AGC is limited to the IF
AGC range. Usually the field strength from the level detector is used in FM mode and
the AGC field strength is used in AM mode.
Table 22. Field Strength Selection
Search Stop Detector
12
Field Strength Narrow Band / Wide Band
Bit 80
Fieldstrength at Pin 26 (wide band)
Fieldstrength from IF-AGC (narrow band)
0
1
A search stop detector is available in AM and FM/WB mode. A STOP condition is
signaled if the frequency of the ZF signal is within a window around the center frequency
of 450 kHz. The width of this search stop window can be set by Bit 85 to 87 in the range
of 0.5 kHz to 80 kHz. The frequency of the ZF signal is measured by counting the number of periods of the ZF signal during a measurement time which is determined by Bit 73
to 78. The inverted STOP signal is available at Pin 21 according to Table 25. The frequency of 10.25 MHz at Pin 22 is used as time reference.
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Table 23. Search Stop Detector Measurement Time
Time Window for Stop Signal
1 ´ 3.1969 ms
Bit 78
0
Bit 77
0
Bit 76
0
Bit 75
0
Bit 74
0
Bit 73
1
.....
63 ´ 3.1969 ms
1
1
1
1
1
1
Table 24. Search Stop Window
Search Stop Window
Bit 87
Bit 86
Bit 85
± 0.5 kHz
± 1.1 kHz
0
0
0
0
0
1
± 2.3 kHz
± 4.8 kHz
0
0
1
1
0
1
± 10 kHz
± 20 kHz
1
1
0
0
0
1
± 40 kHz
± 80 kHz
1
1
1
1
0
1
Table 25. Signals Available at Digital Output Pin 21
Deviation Sensor
Bit 88
0
Bit 92
0 (AM)
INT (Pin 21)
1
0
1
1 (FM/WB)
0 (AM)
NOT MPINT
NOT STOP
1
1 (FM/WB)
NOT (STOP AND NOT MPINT)
The deviation sensor is active in AM and FM/WB mode and measures the modulation of
the signal. It is implemented as a peak detector of the lowpass-filtered MPX signal (see
Figure 7). The output voltage at Pin 31 is proportional to the frequency deviation in
FM/WB or the modulation depth in AM respectively.
Figure 7. Deviation Sensor
+
MPX
4k
Pin 31
25k
13
4519C–AUDR–07/02
Adjacent Channel
Sensor
The adjacent channel sensor is active in FM mode only and measures the field strength
outside the reception band. By setting the center frequency of the band filter of the adjacent channel sensor below or above the 2 nd IF frequency (Bit 5, Bit 6), it can be
determined whether the disturbance signal is located above or below the reception frequency (see Table 28). The bandwidth of the band filter used in the adjacent channel
sensor can be changed by means of Bit 10 to 13. If Bit 4 = 0 the default bandwidth setting is used. The output of the adjacent channel sensor is independent of the bandwidth
setting of the integrated FM band filter.
Figure 8. Adjacent Channel Sensor
IF
intergr. FM bandfilter
+
+
4k
log
Pin 10
50k
log
Table 26. Bandwidth of the Adjacent Channel Detector Filter
BW Adjustment
3 kHz
Bit 13
0
Bit 12
0
Bit 11
0
Bit 10
0
16 kHz
32 kHz
0
0
0
1
1
0
0
0
50 kHz
65 kHz
0
1
1
0
1
0
0
0
80 kHz
95 kHz
1
1
0
1
1
0
0
0
110 kHz
50 kHz
1
0
1
0
1
0
0
1
65 kHz
80 kHz (default)
0
0
0
1
1
0
1
1
95 kHz
110 kHz
0
1
1
0
1
0
1
1
130 kHz
145 kHz
1
1
0
1
1
0
1
1
160 kHz
1
1
1
1
Table 27. Center Frequency Adjacent Channel Sensor
14
Center Frequency
Bit 6
Bit 5
450 kHz
300 kHz
0
0
0
1
700 kHz
Filter OFF
1
1
0
1
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Table 28. Output Voltage of Adjacent Channel Sensor for Different Receiving
Conditions and Center Frequencies
Multipath Sensor
Adjacent Channel Disturbance
no
300 kHz
high
450 kHz
low
600 kHz
high
below
above
high
low
high
high
low
high
The multipath sensor is active in FM mode only and measures the disturbance due to
multipath reception. The multipath sensor detects drops in the field strength after the
integrated band filter by calculating the difference between an averaged maximum field
strength and the current field strength. The maximum depth of these drops is represented by the voltage of the peak detector at Pin 40 (MULTIP). The level of this voltage
represents the degree of disturbance in the received signal.
Figure 9. Multipath Sensor
+
4k
Pin40
A Multipath Noise Canceller (MNC) is implemented to reduce disturbance of the
received signal in multipath reception conditions. If the difference between the momentary and the averaged field strength falls below a threshold adjustable by Bit 81 to 84
(see Table 30), the MPX signal may be muted and this situation (MPINT) can be signalized at Pin 21 (INT) according to Table 25. Muting of the MPX signal during multipath
disturbances can be activated be setting Bit 8.
Table 29. Multipath Noise Canceller
Multipath Noise Canceller
Bit 8
Active
Not active
0
1
15
4519C–AUDR–07/02
Table 30. Sensitivity of the MNC
Sensitivity MNC (Threshold)
Off
Bit 93
x
Bit 92
1
Bit 84
0
Bit 83
0
Bit 82
0
Bit 81
0
Low
x
x
1
1
0
0
0
0
0
1
1
0
(-18 dB)
x
x
1
1
0
0
0
1
1
0
1
0
x
x
1
1
0
0
1
1
0
1
1
0
x
x
1
1
0
1
1
0
1
0
1
0
x
x
1
1
1
1
0
0
0
1
1
0
x
x
1
1
1
1
0
1
1
0
1
0
x
x
1
1
1
1
1
1
0
1
1
0
x
1
1
1
1
1
Normal (-12 dB)
High (-9 dB)
3-wire Bus Description
The register settings of U4255BM-M are programmed by a 3-wire bus protocol. The bus
protocol consists of separate commands. A defined number of bits is transmitted
sequentially during each command.
One command is used to program all bits of one register. The different registers available (see Table 31) are addressed by the length of the command (number of transmitted
bits) and by three address bits that are unique for each register of a given length. 8-bit
registers are programmed by 8-bit commands and 24-bit registers are programmed by
24-bit commands.
Each bus command starts with a rising edge on the enable line (EN) and ends with a
falling edge on EN. EN has to be kept HIGH during the bus command.
The sequence of transmitted bits during one command starts with the LSB of the first
byte and ends with the MSB of the last byte of the register addressed. The DATA is
evaluated at the rising edges of CLK. The number of LOW to HIGH transitions on CLK
during the HIGH period of EN is used to determine the length of the command.
The bus protocol and the register addressing of U4255BM-M are compatible to the
addressing used in U4256BM. That means U4255BM-M and U4256BM can be operated
on the same 3-wire bus as shown in the application circuit.
16
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Figure 10. Pulse Diagram
8-bit command
EN
DATA
LSB
BYTE 1
MSB
BYTE 1
MSB LSB
CLK
24-bit command
EN
DATA
LSB
BYTE 2
MSB LSB
BYTE 3
MSB
CLK
Figure 11. Bus Timing
tR
tF
Enable
tHEN
tS
tR
tF
Data
tHDA
tS
tR
tF
Clock
tH
tL
17
4519C–AUDR–07/02
Data Transfer
Table 31. Control Registers
A24_100
M
S
B
ADDR.
1
LS
B
BYTE 3
0
Gain FM
IF amplifier
AM/FM/WB
0
AM
FM
B9
3
B9
2
B9
1
B9
0
MSB
Sear
ch
B8
9
B88
LS
B
MSB
LS
B
BYTE 2
OSC divider/multipath
sensitivity
Width of window
B8
7
B8
6
B8
5
B8
4
B8
3
B8
2
B8
1
MSB
LS
B
BYTE 1
Field
stren
gth
BWM
PX
B80
B79
Time window stop signal
B7
8
B7
7
B7
6
B7
5
B7
4
B7
3
A24_101
M
S
B
BYTE 3
WBDemodGain
ADDR.
1
0
Smu
te
TkFM IF
B6
8
B67
B66
LS
B
MSB
Start Smute
LS
B
BYTE 2
FM-AGC
AM-AGC
MSB
FM BW 2nd
mixer
LS
B
BYTE 1
IF2 center frequency
MP
FS
FM
ext
De
m.
Adj.
Not
use
d
B5
5
B5
4
B5
3
B5
2
1
x
B7
2
B7
1
B7
0
B6
9
B6
5
B6
4
B6
3
B6
2
B6
1
B6
0
B59
LS
B
MSB
B58
B5
7
B5
6
A24_111
M
S
B
BYTE 3
ADDR.
1
1
BYTE 2
used in test mode only
1
B3
0
B2
9
B2
8
B2
7
B2
6
B25
B24
bandwidth adj. channel
sensor
center frequency of bandfilter
x
x
B2
3
B2
2
B2
1
B2
0
B1
9
B1
8
LS
B
BYTE 1
1
0
0
0
0
1
0
1
B17
B16
B1
5
B1
4
B1
3
B1
2
B1
1
B1
0
A8_100
M
S
B
Tes
t
ADDR.
1
LS
B
BYTE 1
0
0
MP
off
Mut
e
B8
B7
Adj.
channel
sensor
0
B9
B6
B5
A8_101
M
S
B
Optimi
ze
ADDR.
1
0
Band width
1
B4
18
LS
B
BYTE 1
B3
B2
B1
B0
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Absolute Maximum Ratings
All voltages are referred to GND (Pin 25)
Parameters
Symbol
Value
Unit
VS
10
V
Ptot
1000
mW
Tj
150
°C
Ambient temperature range
Tamb
-40 to +85
°C
Storage temperature range
Tstg
-50 to +150
°C
Symbol
Value
Unit
RthJA
60
K/W
Supply voltage
Pin 42
Power dissipation
Junction temperature
Thermal Resistance
Parameters
Junction ambient, soldered to PCB
Operating Range
All voltages are referred to GND (Pin 25)
Parameters
Supply voltage range
Pin 42
Ambient temperature
Symbol
Min.
Typ.
Max.
Unit
VS
7.5
8.5
10
V
Tamb
-40
+85
°C
Electrical Characteristics
Test conditions (unless otherwise specified): VS = 8.5 V, Tamb = 25°C.
No.
Parameters
Test Conditions
Pin
Symbol
Min.
Typ.
Max.
Unit
Type*
42
VS
7.5
8.5
10
V
C
1
Power Supply
1.1
Supply voltage
1.2
Supply current
Standby mode
(Bit 92 = 0, Bit 93 = 0)
42
IStby
20
25
mA
A
1.3
Supply current
Other operation
modes
42
IS
50
60
mA
A
160
MHz
D
2
VCO
2.1
Frequency range
2.2
DC bias voltage
2.3
Buffer output voltage
2.4
Buffer output
resistance
2.5
Buffer output DC
voltage
fVCO
fosc = 120 MHz
70
13
2.8
3.0
3.2
V
A
16
130
150
250
mVrms
A
W
D
V
A
16
16
70
2.8
3.0
3.2
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
19
4519C–AUDR–07/02
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, Tamb = 25°C.
No.
Parameters
3
FM RF-AGC
Test Conditions
Pin
Symbol
Min.
Typ.
Max.
Unit
Type*
3.1
Saturation voltage
No input signal
5
8.3
V
A
3.2
Saturation voltage
No input signal
5
VS-0.2
V
B
3.3
Threshold level
In-band signal
30
dBµV
D
3.4
Maximum threshold
level
Out-of-band signal
(110 MHz),
Bit 64, 65 = 0
1
100
dBmV
A
4
110
102
104
AM RF-AGC, AM Mode (Bit 92 = 0, Bit 93 = 1)
4.1
Saturation voltage
No input signal
7
8.3
V
A
4.2
Saturation voltage
No input signal
7
VS-0.2
V
B
4.3
Output voltage for
minimum gain
Bit 92 = 1
7
6.5
V
A
4.4
Output voltage for
minimum gain
Bit 92 = 1
7
V
B
4.5
Maximum control
voltage
V(Pin 8) = 3 V
6
V
A
4.6
Maximum control
voltage
V(Pin 8) = 3 V
6
VS-1.5
V
B
4.7
Minimum control
voltage
V(Pin 8) = 6 V
6
0.2
0.7
V
A
4.8
Minimum threshold
level
Bits 62, 63 = 0
41
97
99
101
dBµV
A
43, 44
14
16
20
mA
A
4.1
mS
D
5
7.1
VS-1.7
6.5
7.0
7.5
AM Mixer, AM Mode (Bit 92 = 0, Bit 93 = 1)
5.1
Supply current
5.2
Conversion
conductance
5.3
3rd-order input
intercept point
Pin 3 AC-grounded
5.4
Noise figure (SSB)
Generator resistance
2.5 kW (Pin 41)
5.5
Input bias DC voltage
5.6
Input resistance
5.7
Input capacitance
5.8
Maximum output
voltage
5.9
Output resistance
6
6.8
Sum of current in
Pins 43, 44
3, 41,
43, 44
41
IP3AMmix
132
dBµV
C
43, 44
NFAMmix
14
dB
C
V
A
kW
D
3, 41
2.4
2.6
2.9
Single-ended, Pin 39
AC-grounded
3, 41
pF
D
Differential
43, 44
12
Vpp
D
43, 44
100
kW
D
43, 44
15
mA
A
mS
D
2.5
3, 41
3
FM Mixer (FM Mode (Bit 92 = 1, Bit 93 = 0)
6.1
Supply current
6.2
Conversion
conductance
Sum of current in
Pins 43, 44
1, 2,
43, 44
17.5
20
7
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
20
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, Tamb = 25°C.
No.
Parameters
Test Conditions
6.3
3 -order intercept
point
6.4
Noise figure (DSB)
6.5
Input resistance
6.6
Input capacitance
Pin 2 AC-grounded
6.7
Maximum differential
output vltage
VS = 8.5 V
6.8
Output resistance
7
Pin
Symbol
1, 2
IP3FMmix
43, 44
NFFMmix
Unit
Type*
120
dBmV
C
Generator resistance
200 W
10
dB
C
1, 2
1.6
kW
D
1
5
pF
D
Vpp
D
43, 44
100
kW
D
dB
A
st
1 IF FM Amplifier, FM Mode (Bit 92 = 1, Bit 93 = 0)
Bits 89, 90, 91 = 0
7.2
Temperature
coefficient of gain
Bit 66 = 0
7.3
Temperature
coefficient of gain
Bit 66 = 1
7.4
Input resistance
Pin 39 AC-grounded
38
7.5
Input capacitance
Pin 39 AC-grounded
38
7.6
Output resistance
38, 30
19
21
23
TKmin
0.039
dB/K
D
TKmax
0.044
dB/K
D
W
D
pF
D
W
D
16
dB
D
26
dB
D
20
dB
C
kW
D
pF
D
270
330
400
5
30
270
330
400
st
1 IF AM Amplifier, AM Mode (Bit 92 = 0, Bit 93 = 1)
8.1
Maximum voltage
gain
8.2
Gain control range
8.3
Noise figure
8.4
Input resistance
8.5
Input capacitance
9
Max.
12
Minimum voltage gain
8.6
Typ.
43, 44
7.1
8
Min.
rd
330 W load at Pin 30
30, 33
Generator resistance
2.5 kW
NFIFAM
33
Pin 39 AC-grounded
Output resistance
10
33
1
30
270
330
400
W
D
23, 24
10
14
16
mA
A
23, 24
8
10
12
mA
D
2
mS
D
2nd Mixer
9.1
FM supply current
Bit 92 = 1, Bit 93 = 0
9.2
AM/WB supply
current
Bit 92 = 0, Bit 93 = 1
9.3
Conversion
conductance
9.4
Noise figure (SSB)
9.5
3rd-order input
intercept point
9.6
AM/WB output
resistance
Bit 92 = 0, Bit 93 = 1
9.7
Maximum differential
output voltage
AM/WB
VS = 8.5 V
26, 23,
24
Generator resistance
330 W (Pin 26)
23, 24
NFMix2
23
dB
C
26
IP3Mix2
132
dBµV
C
23, 24
100
kW
D
23, 24
12
Vpp
D
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
21
4519C–AUDR–07/02
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, Tamb = 25°C.
No.
Parameters
9.8
Maximum differential
output voltage FM
Test Conditions
Pin
Symbol
Min.
23, 24
1
9.9
Input resistance
26
270
9.10
LO input voltage
22
80
9.11
LO input resistance
22
9.12
LO input bias voltage
22
10
2
nd
Input resistance
Pin 27 AC-grounded
10.2
Maximum voltage
gain
AM/WB mode
(Bit 93 = 1)
10.3
Gain control range
AM/WB mode
(Bit 93 = 1)
10.4
Maximum voltage
gain
FM mode (Bit 92 = 1,
Bit 93 = 0, Bit 54 = 0)
10.5
DC output voltage
10.6
AC output voltage
11
Max.
Type*
Vpp
D
400
W
D
500
mVpp
D
kW
D
V
A
kW
D
dB
A
44
dB
D
37
dB
D
330
1
2.8
Unit
3.0
3.2
IF Amplifier (Bit 55 = 0)
10.1
10.7
Typ.
Output impedance
28
3
28, 20
44
23, 24
20
47
50
20
3.1
3.4
3.7
V
A
Unmodulated signal,
82 dBµV at Pin 1
(IF AGC active)
20
145
175
200
mVrms
A
Small signal
20
W
D
70
nd
FM Demodulator Integrated Bandfilter, FM Mode (Bit 92 = 1, Bit 93 = 0), BW Setting 2
IF Filter = 120 kHz
11.1
AC output voltage
Deviation = ± 75 kHz,
fmod = 1 kHz
11
420
480
540
mVrms
A
11.2
Stereo roll-off
Deviation = ± 75 kHz,
fmod = 38 kHz
(reference: 1 kHz)
11
-2.3
-2.0
-1.7
dB
A
0.4
0.7
%
A
dB
A
11.3
Total harmonic
distortion
Deviation = ± 75 kHz,
fmod = 1 kHz
11
THDFM
11.4
Maximum signal-tonoise ratio
Dev. = ± 22.5 kHz,
fmod = 1 kHz, 50 µs
de-emphase, signal
input at 450 kHz
11
(S/N)FM
12
62
65
Soft Mute, FM Mode (Bit 92 = 1, Bit 93 = 0, Bit 80 = 0)
12.1
Mute gain
Bit 67 = 0,
V (Pin 34) = 2 V
11
-31
-28
-26
dB
A
12.2
Mute gain
Bit 67 = 1,
V (Pin 34) = 2 V
11
-26
-24
-22
dB
A
12.3
Soft mute threshold
Bits 89-91 = 0,
Bits 68-70 = 1
1
50
53
56
dBµV
B
350
400
450
mVrms
A
0.6
2
%
A
13
AM Demodulator, AM Mode (Bit 92 = 0, Bit 93 = 1)
13.1
AC output voltage
Modulation depth =
80%, fmod = 1 kHz
11
13.2
Total harmonic
distortion
Modulation depth =
80%, fmod = 1 kHz,
V(Pin 35) = const.
11
THDAM
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
22
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, Tamb = 25°C.
No.
Parameters
Test Conditions
Pin
Symbol
Min.
Typ.
13.3
Maximum signal-tonoise ratio
Modulation depth =
80%, fmod = 1 kHz,
74 dBµV at Pin 41
11
(S/N)AM
52
54
2.15
2.25
14
DC output voltage
Bit 7 = 1
11
14.2
Mute gain
Bit 7 = 1,
FM dev. = ± 75 kHz,
fmod = 1 kHz
11
-70
Small signal
11
60
15
Output resistance
LOW saturation
voltage
21
0
15.2
LOW output
resistance
21
0.3
15.3
HIGH saturation
voltage
21
15.4
HIGH output
resistance
4.5
21
dB
A
2.4
V
A
-50
dB
A
W
D
V
A
kW
D
4.75
V
A
kW
D
0.5
5.0
1
Deviation Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0)
16.1
Offset voltage
FM dev. = ±0 kHz
31
16.2
Output voltage
FM dev. = ±75 kHz,
fmod = 1 kHz
31
17
Type*
Search Stop Detector, INT Output
15.1
16
Unit
MPX Output
14.1
14.3
Max.
1.7
20
150
mV
A
2.0
2.5
V
A
Field Strength Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0, Bit 89-91 = 0, Bit 80 = 0)
17.1
Offset voltage
No signal
9
0.4
0.75
1.1
V
A
17.2
Output voltage
Unmodulated signal
84 dBµV at Pin 1
9
2.7
3.0
3.3
V
A
9
0.7
0.9
1.1
V
A
9
2.3
2.5
2.7
V
A
20
200
mV
A
1.8
2.2
V
A
Field Strength Sensor, AM Mode (Bit 92 = 0, Bit 93 = 1, Bit 80 = 1)
17.3
Output voltage LOW
field strength
63 dBµV at Pin 28
17.4
Output voltage HIGH
field strength
94 dBµV at Pin 28
18
Multipath Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0)
18.1
Offset voltage
Unmodulated signal,
60 dBµV at Pin 1
40
18.2
Output voltage
AM modulation depth
= 60%,
fmod = 20 kHz,
60 dBµV at Pin 1
40
19
1.4
Adjacent Channel Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0), Bit 4 = 0 (Default BW Setting)
19.1
Offset voltage
Unmodulated signal
10
100
300
mV
A
19.2
Output voltage
FM dev. = ± 50 kHz,
fmod = 1 kHz
10
0.6
1.0
V
A
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
23
4519C–AUDR–07/02
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, Tamb = 25°C.
No.
Parameters
Test Conditions
Pin
19.3
Output voltage
Desired
FM dev. = ± 75 kHz,
fmod = 1 kHz
undesired:
unmodulated
RF level
undesired/desired:
+30 dB frequency
offset = -150 kHz
10
20
Symbol
Input voltage LOW
17, 18,
19
20.2
Input voltage HIGH
17, 18,
19
20.3
Leakage current
20.4
Clock frequency
20.5
Period of CLK
HIGH
LOW
tH
tL
20.6
Rise time
EN, DATA, CLK
tr
20.7
Fall time
EN, DATA, CLK
tf
20.8
Set-up time
ts
20.9
Hold time EN
Hold time DATA
21
Typ.
Max.
Unit
Type*
1.0
1.2
1.6
V
A
0.8
V
D
V
D
3-wire Bus
20.1
20.10
Min.
V = 0 V, 5 V
2.7
17, 18,
19
10
µA
D
18
1.0
MHz
D
ns
ns
D
400
ns
D
100
ns
D
100
ns
D
tHEN
250
ns
D
tHDA
0
ns
D
V
A
250
250
Internally Generated Reference Voltages
21.1
Output voltage
12
5.5
5.7
6.0
21.2
Output voltage
29
3.0
V
D
21.3
Output voltage
27
3.0
V
D
21.4
Output voltage
39
3.0
V
D
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
24
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Diagrams
The following data was measured with the application board (see Figure 20).
In the measurement setup, a 50-W generator is terminated by 50 W and connected to
the antenna input by a 50-W series resistor to achieve 75-W termination at the antenna
input. The generator level specified is the output voltage of this 50-W generator at 50 W
load. If the application board is replaced by a 75-W resistor, the voltage at this resistor is
6 dB below the specified voltage level of the 50 W generator.
Figure 12. FM Demodulator
Integrated bandfilter BW setting: 120 kHz, Bits 0 to 2 = 0, Bit 3 = 1;
1 kHz modulation frequency; 50 ms de-emphasis (THD)
1.0
1
0.9
0.9
MPX output voltage ( Vrms )
0.8
0.8
+85°C
0.7
0.6
0.6
-40°C
0.5
0.5
MPX
0.4
0.4
THD
0.3
THD ( % )
0.7
0.3
-40°C
0.2
0.2
+85°C
0.1
0.1
0.0
0
10
20
30
40
50
60
70
80
90
0
100
Frequency deviation ( kHz )
Figure 13. Multipath Sensor
AM modulation frequency 20 kHz; generator level 40 dBmV
5.0
Sensor Output Voltage (V)
4.5
4.0
3.5
3.0
+85°C
-40°C
2.5
2.0
+25°C
1.5
1.0
0.5
0.0
0
20
40
60
80
100
AM Modulation Depth (%)
25
4519C–AUDR–07/02
Figure 14. Multipath Sensor Frequency Response
Generator level 40 dBmV
Sensor Output Voltage (V]
5.0
4.5
90% at +85°C
90% at +25°C
4.0
90% at -40°C
3.5
3.0
2.5
60% at +85°C
60% at +25°C
60% at -40°C
2.0
1.5
1.0
0.5
0.0
100
1000
10000
100000
AM Modulation Frequency (Hz)
Figure 15. Deviation Sensor
FM modulation frequency: 1 kHz; BW setting 2nd IF filter = 120 kHz
5
Deviation sensor
output voltage (V)
4
+85°C
3
2
-40°C
1
0
0
20000
40000
60000
80000
100000
Frequency deviation (Hz)
26
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Figure 16. Deviation Sensor Frequency Response
FM frequency deviation: 22.5 kHz
Sensor output voltage ( V )
1.0
0.5
0.0
100
1000
10000
100000
FM modulation frequency (Hz)
Figure 17. FM Input Level Sweep
Soft mute threshold Bits 68, 69 = 0, Bit 70 = 1; soft mute gain Bit 67 = 1
gain FM IF amplifier Bit 89 = 1, Bits 90, 91 = 0
10
5
0
4.5
Signal
4
-20
3.5
Sensor output
-30
3
-40
2.5
-50
2
Noise
-60
Fieldstrength sensor
output voltage (V)
MPX output (dB)
-10
1.5
-70
-20
0
20
40
60
80
100
1
120
Input level (dBµV)
27
4519C–AUDR–07/02
Figure 18. Selectivity
Integrated bandfilter BW setting: 120 kHz
desired signal level adjusted to 40 dB S/N without undesired signal
undesired signal level adjusted to 26 dB S/N
4.5
Pdes/Pundes ( dB )
10
4
Pdes/Pundes
0
3.5
-10
3
-20
2.5
-30
2
-40
1.5
Adjacent
-50
1
-60
0.5
-70
-250
-200
-150
-100
-50
0
50
100
150
200
Adjacent channel output
voltage ( V )
20
0
250
Frequency offset ( kHz )
28
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Figure 19. Test Circuit
Test Point
1
44
2
43
3
42
VS
4
41
P41
10n
5
40
6
39
7
38
8
37
330
VS
VS
4n7
1k
270
2k2
100
600
100n
100p
P29
100n
10
9
36
10
35
10n
2n2
100n
10n
P41
11
12
6p8
100n
13
47p
10k
5k6
U4255BM-B
15p
100n
100n
34
200k
P29
33
100n
32
P31
14
31
15
30
16
29
22p
1n
V
P29
22n
10k
220n
10k
Bus
17
28
18
27
19
26
20
25
21
24
220n
Pin1
U4256BM
Pin19
Pin15
10n
10k
VS
10n
22
82p
2k2
23
29
4519C–AUDR–07/02
30
FM 75 Ohm
Ant
R307
47
T111
J109
T302
BC848
S391D
D302
4u7
L301
S391D
D301
100n
C311
10n
220n
BC
858C
T301
T102
BC858
C302
2k2
R308
R105
100
100uH
C315
R306
470k
220n
C316
L303
2m2
2k2
R311
6p8
C319
L302
2u2
C106
L102
10p
C113
100n
3p9
C102
F201
2
43
1n
C56
F101
S391D
10n
D103 C103
D101
BB804
27p
C104
10n
18p
C107
6p8
C108 C109
1
44
100p
C in F201
BB804
D102
T101
BFR93A
R112 47k
R104
470
F102
68k
R102
390
R313
470n
C111
C112
10u
R103
1k
10n
C117
R115
1k
12p
C306
10n
C209
R29
10
4
41
68k
R122
68k
R121
C314
10n
C110
4n7
3
42
10n
C307
100n
C201
5
40
C308
100n
6
39
R34
27
7
38
X301
12
C116
100n
C115
100n
R151
8k2
14
15
30
22p
1n
C152
330p
C134
R131
5k6
BB804
F131
47p
1
20
C131 C132
13
31
220n
C207
220n
C208
32
D131
C133
6p8
220n
11
22u
10
U4255BM
33
C114
9
10u
35
34
C205
10n
C206
1k5
R305
C203
8
36
470n
C204
R111
200k
C202
37
1u
KR201
R304
1k3
3
18
17
28
C158
10n
10n
C151
2
19
16
29
KR202
4
17
18
27
16
19
26
20
25
10n
C159
DAC3
5
21
15
6
1n
10n
C312
8
13
9
12
Q151
12p*
10
11
12p*
10,25MHz
C153 C154
22
23
F302
R106
10
10n
C157
SWO1
SWO3
SWO2
SWO4
7
14
100n
R303
1k
C310
24
C155
C156
10n
C309
220n
U4256BM
KF302
GND
EN
CLK
DATA
IF2OUT
INT
DEV
MULTIP
VS (+8,5V...10,5V)
METER
ADJAC
MPX
*depends on Q151
R152
10
10
R407
Figure 20. Application Circuit
U4255BM-M
4519C–AUDR–07/02
U4255BM-M
Ordering Information
Extended Type Number
Package
Remarks
U4255BM-MFN
SSO44
Tube
U4255BM-MFNG3
SSO44
Taped and reeled
Package Information
9.15
8.65
Package SSO44
Dimensions in mm
18.05
17.80
7.50
7.30
2.35
0.3
0.25
0.10
0.8
16.8
44
0.25
10.50
10.20
23
technical drawings
according to DIN
specifications
1
22
31
4519C–AUDR–07/02
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4519C–AUDR–07/02
xM