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.
Description
The ATR4255 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.
AM/FM
Receiver IC
ATR4255
Rev. 4837A–AUDR–10/04
2 ATR4255
4837A–AUDR–10/04
Figure 1. Block Diagram
Pin Configuration
Figure 2. Pinning SSO44
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
IF1AMIIF1OUT
V3
39 33
AGC
15
16
14
1
MX1FMA
OSCOUT
GNDOSC
OSCE
13
OSCB
MX1OB
44
FM
Divider
AM
FM
OSC
AGC
V3
Bus
FMAGCEN
CLKDATA
17 18 19 5
Bandgap
METER
V57GNDVS
12 25 42 9
V3
ADJACMX2LO
22 10
DEV
INT MULTIP SMUTE
21 40 34 31
INT
Adj.
chan
.Stop
Multi-
path
AGC
AM
dem. 32
36
35
37
11
OPLPF
IFAGCL
IFAGCCH
FILADJ
MPX
Automatic
adjustment
Soft
mute
Dev.
ana.
FM
dem.
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
MX1AMA
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
3
ATR4255
4837A–AUDR–10/04
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
6AMVREGAM 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 5.7 V 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 3 V reference for AMPIN, AMIFAGC, Control, IF2IN
28 IF2IN 2nd IF amplifier input
29 V3 3 V 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, MX1AM A, MX1AM B
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
4 ATR4255
4837A–AUDR–10/04
Functional Description
The ATR4255 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 mul-
tiplex 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 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 17. 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.
In FM mode the FM mixer, the FM RF-AGC and the 1st 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 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
AM/FM/Weather Channel Bit 93 Bit 92
Standby 0 0
FM 0 1
AM 1 0
Weather band 1 1
5
ATR4255
4837A–AUDR–10/04
Test Mode 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.
VCO An oscillator circuit is implemented to build a VCO as proposed in the application sche-
matic. 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.
Figure 3. FM RF-AGC Bit 92
Table 2. Test Mode
Mode Bit 9
Normal operation 0
Testmode 1
Table 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
AGC B92
PIN Diode
VS Pin 42
Pin 5
C111 R115
6 ATR4255
4837A–AUDR–10/04
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 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.
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.
FM 1st IF Amplifier 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 Ω and fits to
external ceramic filters.
Two different temperature coefficients of the FM IF amplifier can be selected by bit 66.
Table 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 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
7
ATR4255
4837A–AUDR–10/04
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 Ω input resis-
tance 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.
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.
Table 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 7. Temperature Coefficient Setting of FM IF Amplifier
Temperature Coefficient (TC) of the IF Amplifier Bit 66
TKmin 0
TKmax 1
Table 8. 2nd Mixer Output Resistance in FM Mode
Bit 61 Bit 60 Output Resistance (Bit 54 = 0) Output Resistance (Bit 54 = 1)
00 3.3 k
Ω~100 kΩ
0 1 0.63 kΩ0.78 kΩ
1 0 0.47 kΩ0.55 kΩ
1 1 0.29 kΩ0.32 kΩ
Table 9. FM Bandwidth 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 is also depending from the values of the application circuit.
8 ATR4255
4837A–AUDR–10/04
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 selec-
tivity. 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.
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 resistor of about 95 kΩ. This low-pass filtered output signal of the FM demodula-
tor 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 pin 20 (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.
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.
Table 10. 2nd IF Filter in FM Mode
2nd IF Filter Bit 54
Internal filter 0
External and internal filter 1
Table 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)
Table 12. Pin 20 Output Setting
Pin 20 Bit 55
2nd IF output 0
Multipath field strength 1
9
ATR4255
4837A–AUDR–10/04
Figure 4. Automatic IF Center Frequency Adjustment
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
IF Center Bit 59 Bit 58 Bit 57 Bit 56
450.00 kHz 0000
456.25 kHz 0001
461.50 kHz 0010
468.75 kHz 0011
475.00 kHz 0100
481.25 kHz 0101
487.50 kHz 0110
493.75 kHz 0111
450.00 kHz 1000
443.75 kHz 1001
437.50 kHz 1010
431.25 kHz 1011
425.00 kHz 1100
418.75 kHz 1101
412.50 kHz 1110
406.25 kHz 1111
Automatic
frequency
adjustment
FM demod
FM
bandfilter
Adj. channel
sensor
+
+
Bits 56 to 59
10.25 MHz
Bits14 to 17
Bits 5, 6
center
freq.
center
freq.
center
freq.
Pin 37
Pin 22
10 ATR4255
4837A–AUDR–10/04
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 (bit 55 = 1) can be used for this purpose.
Table 14. FM Band Filter Center Frequency Correction
IF Correction Bit 17 Bit 16 Bit 15 Bit 14
-0 kHz 000 0
-6.25 kHz 000 1
-12.50 kHz 001 0
-18.75 kHz 001 1
-25.00 kHz 010 0
-31.25 kHz 010 1
-37.50 kHz 011 0
-43.75 kHz 011 1
+0 kHz (default) 1 0 0 0
+6.25 kHz 100 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
Table 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
11
ATR4255
4837A–AUDR–10/04
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 compen-
sate the low frequency deviation in weather band.
An integrated demodulator fine adjustment allows automatic fine tuning of the demodu-
lator 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
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 0 0
15 dB 0 1
18 dB 1 0
21 dB 1 1
Table 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
12 ATR4255
4837A–AUDR–10/04
Soft Mute The soft mute functionality is implemented to reduce the output level of the FM demodu-
lator 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 bit 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.
Figure 6. Soft Mute
Table 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 19. Maximum Soft Mute
Maximum Value of Soft Mute Bit 67
28 dB 0
24 dB 1
Pin 34
Pin 29
+
V3
Bit 67
FS (pin 9)
Bits 68 to 70 Gain FM demodulator
13
ATR4255
4837A–AUDR–10/04
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 bit 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.
Receiving Condition
Analyzer
The ATR4255 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 logarith-
mic 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 band-
width 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.
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 by bit 85 to bit 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 bit 78. The inverted STOP signal is available at pin 21 according to Table 25 on
page 14. The frequency of 10.25 MHz at pin 22 is used as time reference.
Table 20. MPX Output Mute
MPX Output Bit 7
MPX out, pin 11 normal operation 0
Mute ON 1
Table 21. MPX Output Bandwidth
Bandwidth MPX Lowpass Filter Bit 79
90 kHz 0
180 kHz 1
Table 22. Field Strength Selection
Field Strength Narrow Band/Wide Band Bit 80
Fieldstrength at pin 26 (wide band) 0
Fieldstrength from IF-AGC (narrow band) 1
14 ATR4255
4837A–AUDR–10/04
Deviation Sensor 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
Table 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 0 0 0 0 0 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 0 0 0
±1.1 kHz 0 0 1
±2.3 kHz 0 1 0
±4.8 kHz 0 1 1
±10 kHz 1 0 0
±20 kHz 1 0 1
±40 kHz 1 1 0
±80 kHz 1 1 1
Table 25. Signals Available at Digital Output Pin 21
Bit 88 Bit 92 INT (Pin 21)
00 (AM) 1
0 1 (FM/WB) NOT MPINT
10 (AM) NOT STOP
1 1 (FM/WB) NOT (STOP AND NOT MPINT)
MPX
Pin 31
4k
25k
+
15
ATR4255
4837A–AUDR–10/04
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 adja-
cent channel sensor below or above the 2nd IF frequency (bit 5, bit 6), it can be
determined whether the disturbance signal is located above or below the reception fre-
quency (see Table 28 on page 16). 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 band-
width 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
Table 26. Bandwidth of the Adjacent Channel Detector Filter
BW Adjustment Bit 13 Bit 12 Bit 11 Bit 10
3 kHz 0 0 0 0
16 kHz 0 0 1 0
32 kHz 0 1 0 0
50 kHz 0 1 1 0
65 kHz 1 0 0 0
80 kHz 1 0 1 0
95 kHz 1 1 0 0
110 kHz 1 1 1 0
50 kHz 0 0 0 1
65 kHz 0 0 1 1
80 kHz (default) 0 1 0 1
95 kHz 0 1 1 1
110 kHz 1 0 0 1
130 kHz 1 0 1 1
145 kHz 1 1 0 1
160 kHz 1 1 1 1
log
intergr. FM bandfilter
IF
log
4k
50k
+
Pin 10
+
-
16 ATR4255
4837A–AUDR–10/04
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 repre-
sented 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
A Multipath Noise Canceller (MNC) is implemented to reduce disturbance of the
received signal in multipath reception conditions. If the difference between the momen-
tary and the averaged field strength falls below a threshold adjustable by bit 81 to bit 84
(see Table 30 on page 17), the MPX signal may be muted and this situation (MPINT)
can be signalized at pin 21 (INT) according to Table 25 on page 14. Muting of the MPX
signal during multipath disturbances can be activated be setting bit 8.
Table 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
Table 28. Output Voltage of Adjacent Channel Sensor for Different Receiving Condi-
tions 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 29. Multipath Noise Canceller
Multipath Noise Canceller Bit 8
Active 0
Not active 1
4 k Pin 40
+
17
ATR4255
4837A–AUDR–10/04
3-wire Bus Description The register settings of ATR4255 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 avail-
able (see Table 31 on page 19) 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 pro-
grammed 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 ATR4255 are compatible to the
addressing used in U4256BM. That means ATR4255 and U4256BM can be operated on
the same 3-wire bus as shown in the application circuit.
Table 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) x 1 0 0 1 1
x10100
x10101
x10110
Normal (-12 dB) x 1 0 1 1 1
x11000
x11001
x11010
x11011
x11100
x11101
x11110
High (-9 dB) x 1 1 1 1 1
18 ATR4255
4837A–AUDR–10/04
Figure 10. Pulse Diagram
Figure 11. Bus Timing
8-bit command
EN
CLK
DATA
LSB MSB
BYTE 1
24-bit command
CLK
DATA
LSB LSB
MSB MSB BYTE 3BYTE 2 MSB
LSBBYTE 1
EN
t
R
t
S
t
HDA
Enable
Data
Clock
t
R
t
S
t
R
t
H
t
L
t
F
t
F
t
F
t
HEN
19
ATR4255
4837A–AUDR–10/04
Data Transfer
Table 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 Smute Smute 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 Band width
101
B4 B3 B2 B1 B0
20 ATR4255
4837A–AUDR–10/04
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
Thermal Resistance
Parameters Symbol Value Unit
Junction ambient, soldered to PCB RthJA 60 K/W
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
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*
1 Power 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
21
ATR4255
4837A–AUDR–10/04
3FM 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) = 3 V 6 6.5 7.0 7.5 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
5 AM Mixer, AM Mode (Bit 92 = 0, Bit 93 = 1)
5.1 Supply current Sum of current in
pins 43, 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, 44 43, 44 15 17.5 20 mA A
6.2 Conversion
conductance
1, 2,
43, 44 7mSD
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, 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
22 ATR4255
4837A–AUDR–10/04
6.3 3rd-order intercept
point 1, 2 IP3FMmix 120 dBµVC
6.4 Noise figure (DSB) Generator resistance
200 Ω43, 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 vltage VS = 8.5 V 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 330 Ω 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
330 Ω (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 = 8.5 V 23, 24 12 Vpp D
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, 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
23
ATR4255
4837A–AUDR–10/04
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
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
Dev. = ±22.5 kHz,
fmod = 1 kHz, 50 µs
de-emphase, 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) = 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 to 91 = 0,
Bits 68 to 70 = 1 1 505356dBµVB
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
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, 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 ATR4255
4837A–AUDR–10/04
13.3 Maximum
signal-to-noise ratio
Modulation depth =
80%, fmod = 1 kHz,
74 dBµV at pin 41
11 (S/N)AM 52 54 dB A
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 4.54.755.0 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, 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 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
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, 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
ATR4255
4837A–AUDR–10/04
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
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 = 0 V, 5 V 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
Electrical Characteristics (Continued)
Test conditions (unless otherwise specified): VS = 8.5 V, 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 ATR4255
4837A–AUDR–10/04
Diagrams The following data was measured with the application board (see Figure 20).
In the measurement setup, a 50-Ω generator is terminated by 50 Ω and connected to the
antenna input by a 50-Ω series resistor to achieve 75-Ω termination at the antenna input.
The generator level specified is the output voltage of this 50-Ω generator at 50 Ω load. If
the application board is replaced by a 75-Ω resistor, the voltage at this resistor is 6 dB
below the specified voltage level of the 50 Ω generator.
Figure 12. 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 13. 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
0 20 40 60 80 100
AM Modulation Depth (%)
Sensor Output Voltage (V)
-40°C
+25°C
+85°C
27
ATR4255
4837A–AUDR–10/04
Figure 14. Multipath Sensor Frequency Response
Note: Generator level 40 dBµV.
Figure 15. Deviation Sensor
Note: FM modulation frequency: 1 kHz; BW setting 2nd IF filter = 120 kHz.
Figure 16. 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 100000
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
Frequency 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)
28 ATR4255
4837A–AUDR–10/04
Figure 17. 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 18. Selectivity
Note: 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.
-70
-60
-50
-40
-30
-20
-10
0
10
-20 0 20 40 60 80 100 120
Input Level (dBµV)
MPX Output (dB)
1
1.5
2
2.5
3
3.5
4
4.5
5
Fieldstrength Sensor
Output Voltage (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
29
ATR4255
4837A–AUDR–10/04
Figure 19. 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
U4256BM
Pin1 Pin19
Pin15
Test Point
ATR4255
30 ATR4255
4837A–AUDR–10/04
Figure 20. Application Circuit
12 13
ATR4255
14 15 16 17 18 19 20 21 22
33 32 31 30 29 28 27 26 25 24 2344 43 42 41 40 39 38 37 36 35 34
1 2 3 4 5 6 7 8 9 10 11
18p
C203
22u
C131 C132
F131
BB804
1 2 3 4 5 6 7 8 9 10
U4256BM
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 (+8.5 V to 10.5 V)
R311
2k2 R105
100 R115
1k
T102
BC858
C109C108
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
100µH C306C319
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
C154C153C155
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
C116C115
100n
100n
10n
T301
T302
BC848
T111
J109
T101
BFR93A
Ant
FM 75 ΩS391D
D301
S391D
C201
100n
D131
D102
BB804
1n 6p8
*depends on Q151
31
ATR4255
4837A–AUDR–10/04
Package Information
Ordering Information
Extended Type Number Package Remarks
ATR4255-ILSH SSO44 Tube, lead-free
ATR4255-ILQH 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.
4837A–AUDR–10/04
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Tel: (81) 3-3523-3551
Fax: (81) 3-3523-7581
Memory
2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: 1(408) 441-0311
Fax: 1(408) 436-4314
Microcontrollers
2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: 1(408) 441-0311
Fax: 1(408) 436-4314
La Chantrerie
BP 70602
44306 Nantes Cedex 3, France
Tel: (33) 2-40-18-18-18
Fax: (33) 2-40-18-19-60
ASIC/ASSP/Smart Cards
Zone Industrielle
13106 Rousset Cedex, France
Tel: (33) 4-42-53-60-00
Fax: (33) 4-42-53-60-01
1150 East Cheyenne Mtn. Blvd.
Colorado Springs, CO 80906, USA
Tel: 1(719) 576-3300
Fax: 1(719) 540-1759
Scottish Enterprise Technology Park
Maxwell Building
East Kilbride G75 0QR, Scotland
Tel: (44) 1355-803-000
Fax: (44) 1355-242-743
RF/Automotive
Theresienstrasse 2
Postfach 3535
74025 Heilbronn, Germany
Tel: (49) 71-31-67-0
Fax: (49) 71-31-67-2340
1150 East Cheyenne Mtn. Blvd.
Colorado Springs, CO 80906, USA
Tel: 1(719) 576-3300
Fax: 1(719) 540-1759
Biometrics/Imaging/Hi-Rel MPU/
High Speed Converters/RF Datacom
Avenue de Rochepleine
BP 123
38521 Saint-Egreve Cedex, France
Tel: (33) 4-76-58-30-00
Fax: (33) 4-76-58-34-80
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