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
•Lead-free Package
Electrostatic sensitive device.
Observe precautions for handling.
1. Description
The ATR4255P 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
ATR4256, an automatically aligned high-performance AM/FM tuner can be built.
These ICs are designed for highly sophisticated car radio applications.
AM/FM
Receiver IC
ATR4255P
Rev. 4883B–AUDR–01/06
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4883B–AUDR–01/06
ATR4255P
Figure 1-1. Block Diagram
30 29
MX2IN
MX2OB
AM
4
3
2
7
6
41
26 23
AMAGC
AMVREG
MX1AMA
MX1AMB
GNDMX
MX1FMB
AMPLPF MX1OA IF1FMI
843 38
MX2OA IF2IN V3P IF2OUT
24 28 27 20
IF1REF
IF1AMIIF1OUTV3
39 33
AGC
15
16
14
1
MX1FMA
OSCOUT
GNDOSC
OSCE
13
OSCB
MX1OB
44
FM
Divider
AM
FM
OSC
AGC
V3
Bus
FMAGCEN
CLK
DATA
17 18 19 5
Band gap
METER
V57
GND
VS
12 25 42 9
V3
ADJACMX2LO
22 10
DEVINT MULTIP SMUTE
21 40 34 31
INT
Adjacent
channel Stop
Multi-
path
AGC
AM
dem. 32
36
35
37
11
OPLPF
IFAGCL
IFAGCH
FILADJ
MPX
Automatic
adjustment
Soft
mute
Dev.
analog
FM
dem.
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ATR4255P
2. Pin Configuration
Figure 2-1. Pinning SSO44
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
DEV
IF1OUT
V3
IF2IN
V3P
MX2IN
IF1AMI
OPLPF
GND
SMUTE
IFAGCH
IFAGCL
MX2OA
MX2OB
IF1REF
IF1FMI
FILADJ
MX1AM
A
MULTIP
VS
MX1OA
MX1OB
MX1FMA
MX1FMB
MX1AMB
GNDMX
FMAGC
AMVREG
AMAGC
AMPLPF
METER
ADJAC
MPX
V57
OSCB
OSCE
GNDOSC
OSCOUT
EN
CLK
DATA
IF2OUT
INT
MX2LO
4
4883B–AUDR–01/06
ATR4255P
Table 2-1. Pin Description
Pin Symbol Function
1MX1FMA1
st mixer FM input A
2MX1FMB1
st mixer FM input B
3 MX1AMB 1st mixer AM input B
4 GNDMX Ground 1st mixer, preamplifier AGC
5 FMAGC FM preamplifier AGC
6 AMVREG AM control voltage
7 AMAGC AM preamplifier AGC
8 AMPLPF AM AGC LP filter
9 METER Field strength output
10 ADJAC Adjacent channel detection output
11 MPX Multiplex signal
12 V57 5.7V reference voltage
13 OSCB Oscillator basis
14 OSCE Oscillator emitter
15 GNDOSC Oscillator ground
16 OSCOUT Oscillator output
17 EN 3-wire bus enable
18 CLK 3-wire bus clock
19 DATA 3-wire bus data
20 IF2OUT 2nd IF amplifier output
21 INT Interrupt, stop signal
22 MX2LO 10.25 MHz input for 2nd mixer
23 MX2OB 2nd mixer output B
24 MX2OA 2nd mixer output A
25 GND Ground
26 MX2IN 2nd mixer input
27 V3P 3V reference for AMPIN, AMIFAGC, Control, IF2IN
28 IF2IN 2nd IF amplifier input
29 V3 3V reference for IF1OUT, MX2IN
30 IF1OUT 1st IF amplifier output
31 DEV Deviation detect output, test output
32 OPLPF Operating point LPF
33 IF1AMI 1st IF AM amplifier input
34 SMUTE Soft mute control input
35 IFAGCH IF AGC LP filter high time
36 IFAGCL IF AGC LP filter low time constant
37 FILADJ Filter adjust
38 IF1FMI 1st IF FM amplifier input
39 IF1REF 1st IF and MX1OUT reference, MX1AMA, MX1AMB
40 MULTIP Multipath detection output
41 MX1AMA 1st mixer AM input A
42 VS Supply voltage
43 MX1OA 1st mixer output A
44 MX1OB 1st mixer output B
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ATR4255P
3. Functional Description
The ATR4255P 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-conver-
sion 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 soft mute fea-
ture, 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 cir-
cuit 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. See Section “3-wire Bus
Description” on page 19 for the bus protocol and the bit-to-register mapping. The meaning of the
control bits is described in the following sections.
3.1 Reception Mode
The IC can be operated in four different modes; modes AM, FM, Weather band (WB), and
Standby are selected by means of bits 92 and 93 as shown in Table 3-1.
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.
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 pins 23 and 24 is increased and the input of the 2nd IF
amplifier can be switched between pins 23, 24 and 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 3-1. Operating Mode
AM/FM/Weather Channel Bit 93 Bit 92
Standby 0 0
FM 0 1
AM 1 0
Weather band (WB) 1 1
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ATR4255P
3.2 Test Mode
A special test mode is implemented for final production test only. This mode is activated by set-
ting bit 9 to “1”. This mode is not intended to be used in customer applications. For normal
operation, bit 9 has to be set to “0”. Bits 18 to 30 are deactivated in normal operation mode.
3.3 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 ATR4256. The VCO signal is provided at the
buffered output pin 16 to be fed to the PLL circuit.
3.4 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 3-1) 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 chang-
ing the value of C111.
The AGC threshold level at the input of the FM mixer can be adjusted by bits 64 and 65 as
shown in Table 3-3. 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 using bits 89 to 91.
Figure 3-1. FM RF-AGC Bit 92
Table 3-2. Test Mode
Mode Bit 9
Normal operation 0
Test mode 1
AGC B92
PIN Diode
VS Pin 42
Pin 5
C111 R115
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ATR4255P
3.5 AM RF-AGC
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 inputs
(pin 3, pin 41). This threshold level can be set by bits 62 and 63 (Table 3-4). 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 con-
stant of the AGC control loop can be adjusted by changing the value of the capacitor at pin 8.
3.6 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.
3.7 AM 1st Mixer
The AM 1st mixer is used for up-conversion of the AM reception frequency to the 1st IF fre-
quency. 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 as shown in
Table 3-5.
Table 3-3. FM-AGC Threshold
FM-AGC Threshold Bit 65 Bit 64
104 dBµV 0 0
101 dBµV 0 1
98 dBµV 1 0
92 dBµV 1 1
Table 3-4. AM-AGC Threshold
AM-AGC Threshold Bit 63 Bit 62
99 dBµV 0 0
102 dBµV 0 1
104 dBµV 1 0
105 dBµV 1 1
Table 3-5. Divide Factor of the AM Prescaler
Divider AM Prescaler Bit 93 Bit 92 Bit 84 Bit 83 Bit 82 Bit 81
Divide by 10 1 0 x 0 0 0
Divide by 6 1 0 x 0 0 1
Divide by 7 1 0 x 0 1 0
Divide by 8 1 0 x 1 0 0
Divide by 4 1 0 x 1 0 1
8
4883B–AUDR–01/06
ATR4255P
3.8 FM 1st IF Amplifier
A programmable gain amplifier is used in FM and WB mode between pin 38 and pin 30 to com-
pensate the loss in the external ceramic band filters. The gain of this amplifier is adjusted by
bits 89 to 91 (Table 3-6). The input and the output resistance is 330Ω, and fits to external
ceramic filters.
Two different temperature coefficients (TC) of the FM IF amplifier can be selected by setting
bit 66 (Table 3-7).
3.9 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.
3.10 2nd Mixer
The 2nd mixer is used in AM, FM and WB mode. The mixer input has 330Ω 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 band-
width of the tank at the mixer output. The output resistance can be selected by bits 60 and 61
(Table 3-8).
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 ATR4256.
Table 3-6. Gain of the FM IF Amplifier
Gain FM IF Bit 91 Bit 90 Bit 89
20 dB 0 0 0
22 dB 0 0 1
24 dB 0 1 0
26 dB 0 1 1
28 dB 1 0 0
29 dB 1 0 1
30 dB 1 1 0
31 dB 1 1 1
Table 3-7. Temperature Coefficient Setting of FM IF Amplifier
Temperature Coefficient (TC) of the IF Amplifier Bit 66
TKmin 0
TKmax 1
Table 3-8. 2nd Mixer Output Resistance in FM Mode
Bit 61 Bit 60 Output Resistance (Bit 54 = 0) Output Resistance (Bit 54 = 1)
0 0 3.3 kΩ~100 kΩ
0 1 0.63 kΩ0.78 kΩ
1 0 0.47 kΩ0.55 kΩ
1 1 0.29 kΩ0.32 kΩ
9
4883B–AUDR–01/06
ATR4255P
3.11 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 out-
put (pin 23 and 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”.
3.12 IF-AGC
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.
In FM/WB mode, the output signal of the FM demodulator is applied to pin 35 via a series resis-
tor of about 95 kΩ. 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.
Table 3-9. FM Bandwidth (BW) Mixer 2
Bit 61 Bit 60 FM BW Mixer 2
0 0 150 kHz
0 1 200 kHz
1 0 250 kHz
1 1 450 kHz
Note: The bandwidth also depends on the values of the application circuit.
Table 3-10. 2nd IF Filter in FM Mode
2nd IF Filter Bit 54
Internal filter 0
External and internal filter 1
Table 3-11. IF-AGC Time Constant
Mode Bit 92 Bit 88 IF AGC Time Constant
FM/WB 1 x IFAGCL (fast)
AM reception 0 0 IFAGCH (slow)
AM search 0 1 IFAGCL (fast)
10
4883B–AUDR–01/06
ATR4255P
3.13 2nd IF Output
The 2nd IF after the gain-controlled 2nd IF amplifier is available at pin 20 (bit 55 = 0). In AM
mode, this signal may be used for an external AM stereo decoder. Alternatively, a signal corre-
sponding 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 to “1”.
3.14 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 fre-
quency of 450 kHz. The frequency of 10.25 MHz at pin 22 is used as a reference for this
alignment.
Figure 3-2. Automatic IF Center Frequency Adjustment
For fine tuning, the center frequency of all these integrated active filters (band filter, demodula-
tor, and adjacent channel sensor) can be shifted in steps of 6.25 kHz using bits 56 to 59 (Table
3-13 on page 11). Additionally, the center frequency of the band filter can be adjusted separately
by means of bits 14 to 17, if bit 4 is set to “1”. If bit 4 is set to “0”, the default setting is used.
Table 3-12. Pin 20 Output Setting
Pin 20 Bit 55
2nd IF output 0
Multipath field strength 1
Automatic
frequency
adjustment
FM demod.
FM
band filter
Adj. channel
sensor
+
+
Bit 56 to 59
10.25 MHz
Bit 14 to 17
Bits 5 and 6
Center
freq.
Center
freq.
Center
freq.
Pin 37
Pin 22
11
4883B–AUDR–01/06
ATR4255P
1
Table 3-13. 2nd IF Center Frequency
IF Center Bit 59 Bit 58 Bit 57 Bit 56
450.00 kHz 0 0 0 0
456.25 kHz 0 0 0 1
461.50 kHz 0 0 1 0
468.75 kHz 0 0 1 1
475.00 kHz 0 1 0 0
481.25 kHz 0 1 0 1
487.50 kHz 0 1 1 0
493.75 kHz 0 1 1 1
450.00 kHz 1 0 0 0
443.75 kHz 1 0 0 1
437.50 kHz 1 0 1 0
431.25 kHz 1 0 1 1
425.00 kHz 1 1 0 0
418.75 kHz 1 1 0 1
412.50 kHz 1 1 1 0
406.25 kHz 1 1 1 1
Table 3-14. FM Band Filter Center Frequency Correction
IF Correction Bit 17 Bit 16 Bit 15 Bit 14
–0 kHz 0 0 0 0
–6.25 kHz 0 0 0 1
–12.50 kHz 0 0 1 0
–18.75 kHz 0 0 1 1
–25.00 kHz 0 1 0 0
–31.25 kHz 0 1 0 1
–37.50 kHz 0 1 1 0
–43.75 kHz 0 1 1 1
+0 kHz (default) 1 0 0 0
+6.25 kHz 1 0 0 1
+12.50 kHz 1 0 1 0
+18.75 kHz 1 0 1 1
+25.00 kHz 1 1 0 0
+31.25 kHz 1 1 0 1
+37.50 kHz 1 1 1 0
+43.75 kHz 1 1 1 1
12
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ATR4255P
3.15 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 using
bits 0 to 3 (Table 3-15) to be suitable for the present receiving condition. In WB mode, the band-
width 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 using bits 14 to 17 (bit 4
set to “1”). The field strength after the integrated FM band filter that is available at pin 20
(bit 55 set to “1”) can be used for this purpose.
3.16 FM Demodulator
For weather band reception, the gain of the FM demodulator is increased and can be adjusted
by means of bits 71 and 72 (Table 3-16 on page 13) 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 cen-
ter 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”.
Table 3-15. Bandwidth of the Integrated FM Band Filter
IF Bandwidth Bit 3 Bit 2 Bit 1 Bit 0
200 kHz 0 0 0 0
190 kHz 0 0 0 1
180 kHz 0 0 1 0
170 kHz 0 0 1 1
160 kHz 0 1 0 0
150 kHz 0 1 0 1
140 kHz 0 1 1 0
130 kHz 0 1 1 1
120 kHz 1 0 0 0
110 kHz 1 0 0 1
100 kHz 1 0 1 0
90 kHz 1 0 1 1
80 kHz 1 1 0 0
70 kHz 1 1 0 1
60 kHz 1 1 1 0
50 kHz 1 1 1 1
13
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ATR4255P
Figure 3-3. FM Demodulator Automatic Fine Tuning
The center frequency of the FM demodulator can be adjusted by means of bits 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.
3.17 Soft Mute
The soft mute functionality is implemented to reduce the output level of the FM demodulator at
low input signal levels, and to limit the noise at MPX output at low input signal levels. If the input
level falls below an adjustable threshold, continuously the output of the FM demodulator is con-
tinuously 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 bits 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 pins 34 and 29.
The field strength signal available at pin 9 is used for soft mute. Therefore, the soft mute thresh-
old referred to the input of the FM mixer depends on the gain from FM mixer input to the field
strength sensor.
Table 3-16. Demodulator Gain in Weather Band Mode
Demodulator Gain in Weather Band Mode Relative to FM Mode Bit 72 Bit 71
12 dB 0 0
15 dB 0 1
18 dB 1 0
21 dB 1 1
Table 3-17. Demodulator Fine Adjustment
Demodulator Fine Adjustment Bit 53
Fine tuning ON 0
Fine tuning OFF 1
FM demod.
+(10 nF)
AM
AGC
B92
Center freq.
Bit 53
Automatic
frequency
adjustment
MPX
IFAGCH
V3
14
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ATR4255P
Figure 3-4. Soft Mute
3.18 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” (Table 3-20).
The bandwidth of the low-pass filter at the MPX output can be set to 90 kHz or 180 kHz using
bit 79 (Table 3-21 on page 15).
Table 3-18. Soft Mute Threshold
Relative Soft Mute Threshold Bit 70 Bit 69 Bit 68
Soft mute OFF 0 0 0
–18 dB 0 0 1
–15 dB 0 1 0
–12 dB 0 1 1
–9 dB 1 0 0
–6 dB 1 0 1
–3 dB 1 1 0
0 dB 1 1 1
Table 3-19. Maximum Soft Mute
Maximum Value of Soft Mute Bit 67
28 dB 0
24 dB 1
Pin 34
Pin 29
+
V3
Bit 67FS (Pin 9)
Bits 68 to 70
Gain FM demodulator
Table 3-20. MPX Output Mute
MPX Output Bit 7
MPX out, pin 11 normal operation 0
Mute ON 1
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ATR4255P
3.19 Receiving Condition Analyzer
ATR4255P implements several sensors that provide information about the receiving condition of
the selected station.
3.20 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 when using the level detector because of addi-
tional 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.
3.21 Search Stop Detector
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 in the range of 0.5 kHz to 80 kHz using bits 85 to 87. The
frequency of the ZF signal is measured by counting the number of periods of the ZF signal dur-
ing a measurement time which is determined by the value of bits 73 to 78. The inverted STOP
signal is available at pin 21 as shown in Table 3-25 on page 16. The frequency of 10.25 MHz at
pin 22 is used as time reference.
Table 3-21. MPX Output Bandwidth
Bandwidth MPX Low-pass Filter Bit 79
90 kHz 0
180 kHz 1
Table 3-22. Field Strength Selection
Field Strength Narrow Band/Wide Band Bit 80
Field strength at pin 26 (wide band) 0
Field strength from IF-AGC (narrow band) 1
Table 3-23. Search Stop Detector Measurement Time
Time Window for Stop Signal Bit 78 Bit 77 Bit 76 Bit 75 Bit 74 Bit 73
1 × 3.1969 ms 000001
... ... ... ... ... ... ...
63 × 3.1969 ms 1 1 1 1 1 1
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ATR4255P
3.22 Deviation Sensor
The deviation sensor is active in AM and FM/WB mode and measures the modulation of the sig-
nal. It is implemented as a peak detector of the low-pass–filtered MPX signal (see Figure 3-5).
The output voltage at pin 31 is proportional to the frequency deviation in FM/WB or the
modulation depth in AM.
Figure 3-5. Deviation Sensor
3.23 Adjacent Channel Sensor
The adjacent channel sensor is active only in FM mode, 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 2nd IF frequency (bits 5 and 6), it can be determined whether the dis-
turbance signal is located above or below the reception frequency (see Table 3-28 on page 18).
The bandwidth of the band filter used in the adjacent channel sensor can be changed by means
of bits 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.
Table 3-24. Search Stop Window
Search Stop Window Bit 87 Bit 86 Bit 85
±0.5 kHz 0 0 0
±1.1 kHz 0 0 1
±2.3 kHz 0 1 0
±4.8 kHz 0 1 1
±10 kHz 100
±20 kHz 101
±40 kHz 110
±80 kHz 111
Table 3-25. Signals Available at Digital Output Pin 21
Bit 88 Bit 92 INT (Pin 21)
0 0 (AM) 1
0 1 (FM/WB) NOT MPINT
1 0 (AM) NOT STOP
1 1 (FM/WB) NOT (STOP AND NOT MPINT)
MPX
Pin 31
4k
25k
+
17
4883B–AUDR–01/06
ATR4255P
Figure 3-6. Adjacent Channel Sensor
Table 3-26. Bandwidth (BW) of the Adjacent Channel Detector Filter
BW Adjustment Bit 13 Bit 12 Bit 11 Bit 10
3 kHz 0000
16 kHz 0010
32 kHz 0100
50 kHz 0110
65 kHz 1000
80 kHz 1010
95 kHz 1100
110 kHz 1 1 1 0
50 kHz 0001
65 kHz 0011
80 kHz (default) 0 1 0 1
95 kHz 0111
110 kHz 1 0 0 1
130 kHz 1 0 1 1
145 kHz 1 1 0 1
160 kHz 1 1 1 1
Table 3-27. Center Frequency Adjacent Channel Sensor
Center Frequency Bit 6 Bit 5
450 kHz 0 0
300 kHz 0 1
700 kHz 1 0
Filter OFF 1 1
log
Intergrated FM band filter
IF
lo
g
4k
50k
+
Pin 10
+
-
18
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ATR4255P
3.24 Multipath Sensor
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 3-7. Multipath Sensor
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 an adjustable threshold (adjustable by setting bits 81 to 84, Table 3-30
on page 19), the MPX signal may be muted and this situation (MPINT) can be signaled at pin 21
(INT) as shown in Table 3-25 on page 16. Muting of the MPX signal during multipath distur-
bances can be activated be setting bit 8 (Table 3-29).
Table 3-28. Output Voltage of Adjacent Channel Sensor for Different Receiving Conditions
and Center Frequencies
Adjacent Channel Disturbance 300 kHz 450 kHz 600 kHz
No High Low High
Below High High Low
Above Low High High
Table 3-29. Multipath Noise Canceller
Multipath Noise Canceller Bit 8
Active 0
Not active 1
4k
+
Pin 40
19
4883B–AUDR–01/06
ATR4255P
3.25 3-wire Bus Description
The register settings of ATR4255P 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 3-31 on page 21) 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 ATR4255P are compatible to the addressing
used in ATR4256. That means ATR4255P and ATR4256 can be operated on the same 3-wire
bus as shown in the application circuit.
Table 3-30. Sensitivity of the MNC
Sensitivity MNC (Threshold) Bit 93 Bit 92 Bit 84 Bit 83 Bit 82 Bit 81
Off x10000
Low x10001
... x10010
(–18 dB) x10011
... x10100
... x10101
... x10110
Normal (–12 dB) x10111
... x11000
... x11001
... x11010
... x11011
... x11100
... x11101
... x11110
High (–9 dB) x11111
20
4883B–AUDR–01/06
ATR4255P
Figure 3-8. Pulse Diagram
Figure 3-9. Bus Timing
8-bit command
EN
CLK
DATA LSB MSB
BYTE 1
24-bit command
CLK
DATA LSB LSB
MSB MSB BYTE 3
BYTE 2 MSB
LSBBYTE 1
EN
t
R
Enable
Data
Clock
t
R
t
S
t
R
t
S
t
HDA
t
L
t
H
t
F
t
F
t
F
t
HEN
21
4883B–AUDR–01/06
ATR4255P
3.26 Data Transfer
Table 3-31. Control Registers
A24_100
MSB BYTE 3 LSB MSB BYTE 2 LSB MSB BYTE 1 LSB
ADDR. AM/FM/
WB
Gain FM
IF amplifier Search Width of window OSC divider/multipath
sensitivity
Field
strength
BWM
PX Time window stop signal
100AMFM
B93 B92 B91 B90 B89 B88 B87 B86 B85 B84 B83 B82 B81 B80 B79 B78 B77 B76 B75 B74 B73
A24_101
MSB BYTE 3 LSB MSB BYTE 2 LSB MSB BYTE 1 LSB
ADDR.
WB-
Demod-
Gain
Start soft mute Soft
mute
Tk-FM
IF FM-AGC AM-AGC FM BW 2nd
mixer IF2 center frequency MP
FS
FM
ext
Dem.
Adj.
Not
used
101 x
B72 B71 B70 B69 B68 B67 B66 B65 B64 B63 B62 B61 B60 B59 B58 B57 B56 B55 B54 B53 B52
A24_111
MSB BYTE 3 LSB MSB BYTE 2 LSB MSB BYTE 1 LSB
ADDR. Used in test mode only Center frequency of
bandfilter
Bandwidth adj. channel
sensor
111 xx 1 0000101
B30 B29 B28 B27 B26 B25 B24 B23 B22 B21 B20 B19 B18 B17 B16 B15 B14 B13 B12 B11 B10
A8_100
MSB BYTE 1 LSB
ADDR. Test MPoff Mute
Adj.
channel
sensor
1000
B9 B8 B7 B6 B5
A8_101
MSB BYTE 1 LSB
ADDR. Optimize Bandwidth
101
B4 B3 B2 B1 B0
22
4883B–AUDR–01/06
ATR4255P
4. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
All voltages refer to GND (pin 25).
Parameters Symbol Value Unit
Supply voltage, pin 42 VS10 V
Power dissipation Ptot 1000 mW
Junction temperature Tj150 °C
Ambient temperature range Tamb –40 to +85 °C
Storage temperature range Tstg –50 to +150 °C
5. Thermal Resistance
Parameters Symbol Value Unit
Junction ambient, soldered to PCB RthJA 60 K/W
6. Operating Range
All voltages are referred to GND (pin 25).
Parameters Symbol Min. Typ. Max. Unit
Supply voltage range, pin 42 VS7.5 8.5 10 V
Ambient temperature Tamb –40 +85 °C
7. Electrical Characteristics
Test conditions (unless otherwise specified): VS = 8.5V, Tamb = 25°C.
No. Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Type*
1Power Supply
1.1 Supply voltage 42 VS7.5 8.5 10 V C
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 IS50 60 mA A
2VCO
2.1 Frequency range fVCO 70 160 MHz D
2.2 DC bias voltage 13 2.8 3.0 3.2 V A
2.3 Buffer output voltage fosc = 120 MHz 16 130 150 250 mVrms A
2.4 Buffer output resistance 16 70 ΩD
2.5 Buffer output DC
voltage 16 2.8 3.0 3.2 V A
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
23
4883B–AUDR–01/06
ATR4255P
3 FM RF-AGC
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 30 110 dBµV D
3.4 Maximum threshold
level
Out-of-band signal
(110 MHz),
bit 64, 65 = 0
1 100 102 104 dBµV A
4 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 6.8 7.1 V A
4.4 Output voltage for
minimum gain Bit 92 = 1 7 VS – 1.7 V B
4.5 Maximum control
voltage V(pin 8) = 3V 6 6.5 7.0 7.5 V A
4.6 Maximum control
voltage V(pin 8) = 3V 6 VS – 1.5 V B
4.7 Minimum control
voltage V(pin 8) = 6V 6 0.2 0.7 V A
4.8 Minimum threshold
level Bits 62, 63 = 0 41 97 99 101 dBµV A
5 AM Mixer, AM Mode (Bit 92 = 0, Bit 93 = 1)
5.1 Supply current Sum of current in
pins 43 and 44 43, 44 14 16 20 mA A
5.2 Conversion
conductance
3, 41, 43,
44 4.1 mS D
5.3 3rd-order input intercept
point Pin 3 AC grounded 41 IP3AMmix 132 dBµV C
5.4 Noise figure (SSB) Generator resistance
2.5 kΩ (pin 41) 43, 44 NFAMmix 14 dB C
5.5 Input bias DC voltage 3, 41 2.4 2.6 2.9 V A
5.6 Input resistance Single-ended, pin 39
AC grounded 3, 41 2.5 kΩD
5.7 Input capacitance 3, 41 3 pF D
5.8 Maximum output
voltage Differential 43, 44 12 Vpp D
5.9 Output resistance 43, 44 100 kΩD
6 FM Mixer (FM Mode (Bit 92 = 1, Bit 93 = 0)
6.1 Supply current Sum of current in
pins 43 and 44 43, 44 15 17.5 20 mA A
6.2 Conversion
conductance
1, 2, 43,
44 7mSD
7. Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5V, Tamb = 25°C.
No. Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Type*
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
24
4883B–AUDR–01/06
ATR4255P
6.3 3rd-order intercept point 1, 2 IP3FMmix 120 dBµV C
6.4 Noise figure (DSB) Generator resistance
200Ω43, 44 NFFMmix 10 dB C
6.5 Input resistance 1, 2 1.6 kΩD
6.6 Input capacitance Pin 2 AC grounded 1 5 pF D
6.7 Maximum differential
output voltage VS = 8.5V 43, 44 12 Vpp D
6.8 Output resistance 43, 44 100 kΩD
71
st IF FM Amplifier, FM Mode (Bit 92 = 1, Bit 93 = 0)
7.1 Minimum voltage gain Bits 89, 90, 91 = 0 38, 30 19 21 23 dB A
7.2 Temperature coefficient
of gain Bit 66 = 0 TKmin 0.039 dB/K D
7.3 Temperature coefficient
of gain Bit 66 = 1 TKmax 0.044 dB/K D
7.4 Input resistance Pin 39 AC grounded 38 270 330 400 ΩD
7.5 Input capacitance Pin 39 AC grounded 38 5 pF D
7.6 Output resistance 30 270 330 400 ΩD
81
st IF AM Amplifier, AM Mode (Bit 92 = 0, Bit 93 = 1)
8.1 Maximum voltage gain 330Ω load at pin 30 30, 33 16 dB D
8.2 Gain control range 26 dB D
8.3 Noise figure Generator resistance
2.5 kΩNFIFAM 20 dB C
8.4 Input resistance 33 10 kΩD
8.5 Input capacitance Pin 39 AC grounded 33 1 pF D
8.6 Output resistance 30 270 330 400 ΩD
92
nd Mixer
9.1 FM supply current Bit 92 = 1, bit 93 = 0 23, 24 10 14 16 mA A
9.2 AM/WB supply current Bit 92 = 0, bit 93 = 1 23, 24 8 10 12 mA D
9.3 Conversion
conductance
26, 23,
24 2mSD
9.4 Noise figure (SSB) Generator resistance
330Ω (pin 26) 23, 24 NFMix2 23 dB C
9.5 3rd-order input intercept
point 26 IP3Mix2 132 dBµV C
9.6 AM/WB output
resistance Bit 92 = 0, bit 93 = 1 23, 24 100 kΩD
9.7 Maximum differential
output voltage AM/WB VS = 8.5V 23, 24 12 Vpp D
9.8 Maximum differential
output voltage FM 23, 24 1 Vpp D
9.9 Input resistance 26 270 330 400 ΩD
9.10 LO input voltage 22 80 500 mVpp D
7. Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5V, Tamb = 25°C.
No. Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Type*
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
25
4883B–AUDR–01/06
ATR4255P
9.11 LO input resistance 22 1 kΩD
9.12 LO input bias voltage 22 2.8 3.0 3.2 V A
10 2nd IF Amplifier (Bit 55 = 0)
10.1 Input resistance Pin 27 AC grounded 28 3 kΩD
10.2 Maximum voltage gain AM/WB mode
(bit 93 = 1) 28, 20 44 47 50 dB A
10.3 Gain control range AM/WB mode
(bit 93 = 1) 44 dB D
10.4 Maximum voltage gain FM mode (bit 92 = 1, bit
93 = 0, bit 54 = 0) 23, 24 20 37 dB D
10.5 DC output voltage 20 3.1 3.4 3.7 V A
10.6 AC output voltage
Unmodulated signal,
82 dBµV at pin 1
(IF AGC active)
20 145 175 200 mVrms A
10.7 Output impedance Small signal 20 70 ΩD
11 FM Demodulator Integrated Bandfilter, FM Mode (Bit 92 = 1, Bit 93 = 0), BW Setting 2nd 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
11.3 Total harmonic
distortion
Deviation = ±75 kHz,
fmod = 1 kHz 11 THDFM 0.4 0.7 % A
11.4
Maximum
signal-to-noise ratio
(SNR)
Dev. = ±22.5 kHz,
fmod = 1 kHz, 50 µs de-
emphasize, signal input
at 450 kHz
11 (S/N)FM 62 65 dB A
12 Soft Mute, FM Mode (Bit 92 = 1, Bit 93 = 0, Bit 80 = 0)
12.1 Mute gain Bit 67 = 0,
V (pin 34) = 2V 11 –31 –28 –26 dB A
12.2 Mute gain Bit 67 = 1,
V (pin 34) = 2V 11 –26 –24 –22 dB A
12.3 Soft mute threshold Bits 89 to 91 = 0,
Bits 68 to 70 = 1 1505356dBµVB
13 AM Demodulator, AM Mode (Bit 92 = 0, Bit 93 = 1)
13.1 AC output voltage Modulation depth =
80%, fmod = 1 kHz 11 350 400 450 mVrms A
13.2 Total harmonic
distortion
Modulation depth =
80%, fmod = 1 kHz,
V(pin 35) = const.
11 THDAM 0.6 2 % A
13.3
Maximum
signal-to-noise ratio
(SNR)
Modulation depth =
80%, fmod = 1 kHz,
74 dBµV at pin 41
11 (S/N)AM 52 54 dB A
7. Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5V, Tamb = 25°C.
No. Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Type*
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
26
4883B–AUDR–01/06
ATR4255P
14 MPX Output
14.1 DC output voltage Bit 7 = 1 11 2.15 2.25 2.4 V A
14.2 Mute gain
Bit 7 = 1,
FM dev. = ±75 kHz,
fmod = 1 kHz
11 –70 –50 dB A
14.3 Output resistance Small signal 11 60 ΩD
15 Search Stop Detector, INT Output
15.1 LOW saturation voltage 21 0 0.5 V A
15.2 LOW output resistance 21 0.3 kΩD
15.3 HIGH saturation voltage 21 4.5 4.75 5.0 V A
15.4 HIGH output resistance 21 1 kΩD
16 Deviation Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0)
16.1 Offset voltage FM dev. = ±0 kHz 31 20 150 mV A
16.2 Output voltage FM dev. = ±75 kHz,
fmod = 1 kHz 31 1.7 2.0 2.5 V A
17 Field Strength Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0, Bits 89 to 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 92.73.03.3VA
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 9 0.7 0.9 1.1 V A
17.4 Output voltage HIGH
field strength 94 dBµV at pin 28 9 2.3 2.5 2.7 V A
18 Multipath Sensor, FM Mode (Bit 92 = 1, Bit 93 = 0)
18.1 Offset voltage Unmodulated signal,
60 dBµV at pin 1 40 20 200 mV A
18.2 Output voltage
AM modulation depth =
60%,
fmod = 20 kHz, 60 dBµV
at pin 1
40 1.4 1.8 2.2 V A
19 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
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 1.0 1.2 1.6 V A
20 3-wire Bus
7. Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5V, Tamb = 25°C.
No. Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Type*
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
27
4883B–AUDR–01/06
ATR4255P
20.1 Input voltage LOW 17, 18,
19 0.8 V D
20.2 Input voltage HIGH 17, 18,
19 2.7 V D
20.3 Leakage current V = 0V, 5V 17, 18,
19 10 µA D
20.4 Clock frequency 18 1.0 MHz D
20.5
Period of CLK
HIGH
LOW
tH
tL
250
250
ns
ns
D
20.6 Rise time
EN, DATA, CLK tr400 ns D
20.7 Fall time
EN, DATA, CLK tf100 ns D
20.8 Set-up time ts100 ns D
20.9 Hold time EN tHEN 250 ns D
20.10 Hold time DATA tHDA 0nsD
21 Internally Generated Reference Voltages
21.1 Output voltage 12 5.5 5.7 6.0 V A
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
7. Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5V, Tamb = 25°C.
No. Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit Type*
*) Type means: A =100% tested, B = 100% correlation tested, C = Characterized on samples, D = Design parameter
28
4883B–AUDR–01/06
ATR4255P
8. Diagrams
The following data was measured with the application board (Figure 8-9 on page 32).
In the measurement setup, a 50Ω generator is terminated by 50Ω and connected to the antenna
input by a 50Ω series resistor to achieve 75Ω termination at the antenna input. The generator
level specified is the output voltage of this 50Ω generator at 50Ω load. If the application board is
replaced by a 75Ω resistor, the voltage at this resistor is 6 dB below the specified voltage level of
the 50Ω generator.
Figure 8-1. FM Demodulator
Note: Integrated bandfilter BW setting: 120 kHz, bits 0 to 2 = 0, bit 3 = 1;
1 kHz modulation frequency; 50 µs de-emphasis (THD).
Figure 8-2. Multipath Sensor
Note: AM modulation frequency 20 kHz; generator level 40 dBµV.
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 10203040 5060708090100
Frequency Deviation (kHz)
MPX Output Voltage (Vrms)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
THD
(
%
)
MPX
THD
+85˚C
-40˚C
+85˚C
-40˚C
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
020406080100
AM Modulation Depth (%)
Sensor Output Voltage (V)
-40˚C
+25˚C
+85˚C
29
4883B–AUDR–01/06
ATR4255P
Figure 8-3. Multipath Sensor Frequency Response
Note: Generator level 40 dBµV.
Figure 8-4. Deviation Sensor
Note: FM modulation frequency: 1 kHz; BW setting 2nd IF filter = 120 kHz.
Figure 8-5. Deviation Sensor Frequency Response
Note: FM frequency deviation: 22.5 kHz.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
100 1000 10000 10000
0
AM Modulation Frequency (Hz)
Sensor Output Voltage (V)
90% at +85˚C
90% at +25˚C
90% at -40˚C
60% at +85˚C
60% at +25˚C
60% at -40˚C
0
1
2
3
4
5
0 20000 40000 60000 80000 100000
Fre
q
uenc
y
Deviation
(
Hz
)
Deviation Sensor
Output Voltage (V)
+85˚C
-40˚C
0.0
0.5
1.0
100 1000 10000 100000
FM Modulation Frequency (Hz)
Sensor Output Voltage (V)
30
4883B–AUDR–01/06
ATR4255P
Figure 8-6. FM Input Level Sweep
Note: Soft mute threshold, bits 68 and 69 = 0, bit 70 = 1; soft mute gain, bit 67 = 1,
gain FM IF amplifier, bit 89 = 1, bits 90 and 91 = 0.
Figure 8-7. Selectivity
Note: Integrated bandfilter BW setting: 120 kHz
Desired signal level adjusted to 40 dB SNR without undesired signal,
undesired signal level adjusted to 26 dB SNR.
-70
-60
-50
-40
-30
-20
-10
0
10
-20 0 20 40 60 80 100 120
In
p
ut Level
(
dB
µ
V
)
MPX Output (dB)
1
1.5
2
2.5
3
3.5
4
4.5
5
Field Strength Sensor
Out
p
ut Volta
g
e
(
V
)
Signal
Sensor output
Noise
-70
-60
-50
-40
-30
-20
-10
0
10
20
-250 -200 -150 -100 -50 0 50 100 150 200 250
Frequency Offset (kHz)
Pdes/Pundes (dB)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Adjacent Channel Output
Voltage (V)
Pdes/Pundes
Adjacent
31
4883B–AUDR–01/06
ATR4255P
Figure 8-8. Test Circuit
330
1k
600
4n7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
24
23
26
25
28
27
30
29
32
31
34
33
36
35
38
37
40
39
42
41
44
43
VS
100n
10n
10n
100n
Bus
10n
10k
VS 82p
VS
VS
100n
P41
10n
100n
100n
100n
220n
47p
22p
6p8
5k6
1n
10k
100
10
15p
100p
270 2k2
100n
P29
200k P29
P31
22n
2k2
10k
2n2
P41
10n
10k
V
220n
P29
ATR4256
Pin1 Pin19
Pin15
Test Point
ATR4255P
32
4883B–AUDR–01/06
ATR4255P
Figure 8-9. Application Circuit
12 13
ATR4255P
14 15 16 17 18 19 20 21 22
33 32 31 30 29 28 27 26 25 24 23
44 43 42 41 40 39 38 37 36 35 34
12345678910 11
18p
C203
22µ
C131 C132
F131
BB804
12345678910
ATR4256
20 19 18 17 16 15 14 13 12 11
C314
10n
F102
C112
10µ C113
100n
SWO1
DAC3
SWO2
SWO3
SWO4
INT
IF2OUT
DATA
CLK
EN
GND
MPX
ADJAC
METER
C310
F302
MULTIP
DEV
C208
C205
C202
F201
Q151
R407
10
R106
10
R152
10
C312
10n
1n
C309
R303
1k
220n
C207
R305
1k5
X301
R304
1k3
R34
27
KR201
R313
390
C111
470n
C in F201
100p
C307
10n
C209
R29
10
C308
100n
VS (+8.5V
to 10.5V)
R311
2k2 R105
100 R115
1k
T102
BC858
C109
C108
R102
68k
C110
4n7
R121
68k
R122
68k
C56
10p
C104
10n
R112 47k
L102
R104
470
C117
C107
2µ2
C106 27p
F101
BB804
D101
C103
C102
10n
C311
100n
R103
1k
3p9
D103
S391D 10n
D302
L301
4µ7
L303
2m2
L302
100 µH C306
C319
12p
6p8
BC
858C
C316 R308
2k2
220n
R307
47
C315
220n
C302
10n
R306
470k
R151
8k2
C152
330p
C134
1n
C151
10n
C158
10n
C159 C157
10n 10n
C154
C153
C155
C156
10n
10.25 MHz
12p*
12p*
100n
C114
220n
C133
6p8
47p 22p
R131
5k6
KF302
KR202
220n
220n
C204
C206
R111
200k
1µ
10n
10µ
470n
C116
C115
100n
100n
10n
T301
T302
BC848
T111
J109
T101
BFR93A
Ant
FM 75Ω
S391D
D301
S391D
C201
100n
D131
D102
BB804
1n 6p8
*depends on Q151
33
4883B–AUDR–01/06
ATR4255P
10. Package Information
9. Ordering Information
Extended Type Number Package Remarks
ATR4255P-ILSY SSO44 Tube, lead-free
ATR4255P-ILQY SSO44 Taped and reeled, lead-free
technical drawings
according to DIN
specifications
Package SSO44
Dimensions in mm
0.25
0.10
0.3
0.8
18.05
17.80
16.8
2.35
9.15
8.65
7.50
7.30
10.50
10.20
0.25
44 23
122
Printed on recycled paper.
4883B–AUDR–01/06
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