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ICs for FM/AM Tuner
AN7259S
FM-IF Amplifier Circuit for Car Radio
s Overview
The AN7259S is an FM-IF/DET IC for car radio/car stereo and has each function necessary for electronictuner.
0.4 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 1.50.2 Unit : mm
and separation control, etc. IF counter output and search output in channel selection signal as electronic tuning and with IF counter output ON/OFF circuit (SSC) * Adjustment of search band width and search output center frequency * Soft muting adjusting function
*
0.10.1
1.27
s Features * Quadrature detection system and fewer external parts * Good linearity of control voltage output used for AGC
0.40.25
0.3
5.40.3 7.70.3
20-Lead SOP Package (SOP020-P-0300A)
s Block Diagram
20 19 18 17 16 15 14 13 12 11
FM IF Amp.
Counter SSC
FM Det.
VCONT.
Search
Mute Amp.
1
2
3
4
5
6
7
8 GND
9
10 VCC
0.15 0.65
12.60.3
AN7259S
s Absolute Maximum Ratings (Ta=25C)
Parameter Supply Voltage Supply Current Power Dissipation (Ta = 75C) Operating Ambient Temperature Storage Temperature Symbol VCC ICC PD Topr Tstg Rating 9.6 23 230 -30 ~ + 75 -55 ~ + 125
ICs for FM/AM Tuner
Unit V mA mW C C
s Recommended Operating Range (Ta=25C)
Parameter Operating Supply Voltage Range Symbol VCC Range 7.3V ~ 9.6V
AN7259S H2
s Electrical Characteristics (VCC = 8V, FM 1kHz 30%Modulation, Ta= 25C)
Parameter Limiting Sensitivity Detection Output Level AFC Offset Voltage Signal Voltage (1) Signal Voltage (2) Signal Voltage (3) Signal Voltage (4) Signal Voltage (5) Search Signal Band Width Supply Current THD THD S/N IF Counter Output Level AMR Residual Noise Level Control Voltage Adjusting Width Reference Voltage AF Output Impedance Symbol Vlim VO Voffset VSIG1 VSIG2 VSIG3 VSIG4 VSIG5 BW Itot Vin = 70dB Vin = 0dB, Pin9 -14 voltage Vin = 0dB, Pin2 voltage VSIG4 -VSIG1 VSIG5 -VSIG4 Vin = 70dB, Pin2 voltage Vin = 100dB, Pin2 voltage Band width at Pin4 DC voltage = 2.5V, R = 30k Vin = 0dB Mod. = 30%, Vin = 100dB Mod. = 100%, Vin = 100dB Mod. = 30%, Vin = 100dB Pin16, 10.7MHz Output AM = 30% Mod., FM = 30% Mod. Vin = 0dB Referred to Input 30 3.9 300 Condition Input at VO = -3dB min. 26.5 150 -240 0.19 2.51 1.15 2.92 4.11 145 15 typ. 29.5 175 0 0.52 2.92 1.45 3.4 4.8 165 19 0.1 0.3 63 250 50 -23 max. 32.5 240 0.85 3.33 1.75 3.98 5.56 185 23 Unit dB mV V V V V V kHz mA % % dB mVrms dB dB dB V
210 mVrms
s Characteristics Curve
Output Voltage, AMR -Vin
20 10 0 -10 AM 1kHz, 30% Modulation -30 -40 -50 -60 -70 -80 0 10 20 30 40 50 60 70 80 90 100 110 120 0 0 10 20 30 40 50 60 70 80 90 100 110 120 0% Modulation (Noise) Vcont (dB) VO (dB) -20 3 2 1 Mute Voltage Pin3 FM 1kHz, 30% Modulation 4 5 Control Voltage Pin2 SD Output Pin4
Control Voltage - Vin
Vin (dB)
Vin (dB)
ICs for FM/AM Tuner
AN7259S
Signal Voltage (1) -Ta
2.0 1.8 1.6 . 1.4 VSIG 1 (V) 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 Ta (C) 60 80 100 120 Vin= 0dB 4.0 VCC 10V 9V 8V 7V VSIG 4 (V) 3.8 VCC 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 -40 -20
Signal Voltage (4) - Ta
10V 9V 8V 7V
Vin=70dB 0 20 40 Ta (C) 60 80 100 120
Signal Voltage (5) - Ta
5.0 4.8 4.6 4.4 BW (kHz) VSIG 5 (V) 4.2 4.0 3.8 3.6 3.4 3.2 Vin=100dB 3.0 -40 -20 0 VCC 10V 9V 8V 7V 20 40 Ta (C) 60 80 100 120 150 140 130 120 110 100 90 80 70 60 50 -40 -20
Search Band Width - Ta
VCC 10V 9V 8V 7V
R14 - 9 = 60k 0 20 40 Ta (C) 60 80 100 120
Limiting Sensitivity - Ta
35 34 33 32 Vlim (dB) Vo (mV) 31 30 29 28 27 26 25 -40 -20 0 20 40 Ta (C) 60 80 100 VCC 10V 9V 8V 7V 120 FM 1kHz 30% Modulation 200 190 180 170 160 150 140 130 120 110 100 -40 -20
Output Voltage - Ta
FM 1kHz 30% Modulation IF T Damp R=1k VCC 10V 9V 8V 7V
0
20
40 Ta (C)
60
80
100
120
Supply Voltage Itot - Ta
25 24 23 22 Itot (mA) 21 20 19 18 17 16 15 -40 -20 0 20 40 Ta (C) 60 80 100 120 3.7 -40 Vin= 0dB VCC 10V 9V 8V 7V Vref (V) 4.1 4.0 3.9 3.8
Reference Voltage Vref -Ta
VCC 10V 9V 8V 7V
-20
0
20
40 Ta (C)
60
80
100
120
AN7259S
s Application Circuit
IF COUNTER OUT 330 200k 200k 0.22F FROM F.E. + 200k 820 15pF SSC REF
ICs for FM/AM Tuner
1.2k
0.022F
20
19
18
17
0.022F 16
15
14
13
12
11
AN7259S
2.2F
22k
1 10kB
2 +
3
4
5
6
7
8 +
9 30kB
10
0.022F
0.022F
100k 0.22F 7.5k + AF OUT 1000pF 0.022F VCC
VCONT. OUT
SEARCH
s Pin Descriptions * Control Signal Output Block
The AN7259S has linear level meter output (control voltage on Pin2) whose dynamic range is about 60dB wider for change of the input. This control voltage is adjustable by the resistor R4 of Pin1. The adjustable range at R4= 0.8k ~ 10k is more than 30dB in conversion of the input. The polarity of the output voltage from Pin3 is reverse to that of the voltage to be output from Pin2. This output from Pin3 requires insertion of a capacitor (C5 = 4.7F) since it is used for soft muting. The search output (right sketch) to be used for channel selection is obtainable on Pin4. The band width of this search output is adjustable. (Refer to Detection Block.) The search stop sensitivity is externally adjustable because the L level value varies with the input signal level.
200 200 10k
1
R4 10kB ~ 20kB 0.022F
2
C4
3
R5 C5 4.7 1.8 F k
4
C6
Search output
0.22 20k F R6
Control voltage output Control voltage Search output
* Soft Mute
Pin7 is the AF output pin, and the emitter follower output of300 in output impedance is obtainable on this pin. Pin6 is the soft mute adjusting pin to adjust the attenuation at the non-input mode. Soft mute here denotes muting by the level signal output from Pin3, and the soft mute response varies with the time constant of this voltage output. The r2 and C12 are related to the weak input S/N and the soft mute ON time, and with increase of the C12 value, the weak input S/N is proportionately improved, but the speed of response accordingly becomes lower. The r1, on the other hand, is related to the soft mute OFF time. Each value specified in the right sketch denotes a recommended value.
Input
Increase of R4 30dB Frequency VCC
200 2k r1 r2 36k GND
3
+ C12 4.7F
5
6
7
VR
8
VREF R13 AF OUT
To VCC
C13
Soft mute adj.
ICs for FM/AM Tuner
* Detection Block
Pin11 and Pin12 constitutes a phase-shifting circuit of the QUAD detector by external circuit.The R7 is a coil damp resistor, and it exerts influences on the noise, THD, and output level. Its recommended value is 1.2k ~ 1.8k. Pin9 is the AFC voltage output pin,and according to the value of R10, the band width of the Pin4 search output can be adjusted. Pin13 is the center frequency adjusting pin of the Pin4 search output, and makes it possible to adjust the center frequency of the search output independently of the coil.
VCC 43k
AN7259S
VCC
9
10
11
C9
12
21k
13
14
VREF
C7
C8 0.2A
15pF VR R8 200k R7 820 1.2 R10 k 30k
C11
R10
R9
VCC
*An Example of Coil Adjusting Method
In case of channel selection by IF counter output In case of channel selection by search output V (9, 14) *** DC voltage between Pin9 and Pin14 Vin *** Level of IF input Pin20 Adjust the coil so that the V (9, 14) at Vin= 0dBbecomes equal to V (9, 14) at Vin= 100dB. Same as above. Thereafter,adjust the center frequency of the search output by the Pin13 VR.
* Reference Voltage (VREF)
The reference voltage (3.9V) is output from Pin14. Remember to bypass it by an external capacitor since this line is used as the power supply line to the limiter.
+ - VREF Limiter
8
14
19
* IF Counter Output SSC
Pin16 is the IF counter output pin, and the output of about 300mVP- P is obtainable on this pin. Because of its high gain, the IF counter output line is separated on the pattern from the Pin20 (IF input) line in order to avoid oscillation trouble. Pin15 is the SSC pin to stop the IF counter, and according to the V SSC level, the IF counter operation changes as shown in the table below. The H level must be 4.2V or higher, and the L level must be 1V or lower. SSC is used for prevention of the bad influences of the IF counter output on the other blocks in the receiving mode. VSSC IF counter H ON L STOP
VREF
20k
15
200k 200k R2 R3
16
C3 IF counter output 200pF SSC IN (from microcomputer)
* IF Input Block
Pin20 is the IF input pin, and the input impedance is set between this pin and Pin17 by R1. Usually a resistor of 330 is used as R1 to secure optimum matching with CF. Pin17 and Pin18 are the internal DC feedback pins, and the high frequency components are bypassed through C1 and C2. Pin19 is the GND pin dedicated to the limiter, and each GND of CF, C2 and C1 must be set close to Pin19. Externally short the GND of Pin19 with the GND of Pin8.
30k 30k
17
18
19
R1 330
20
CF IF in
C2
C1
0.022F 0.022F

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