TDA7421 Datasheet, PDF (35/38 Pages) STMicroelectronics – AM/FM TUNER FOR CAR RADIO AND Hi-Fi APPLICATIONS

Evaluation Board Schematic Circuit (part E)
Supply Voltage (12V)
Gnd
MR1
+Vs
JP1
10u + 100n
2 _F.C.
3 _N.C.
OUT 8.5V ⁴
100n
L4916
56 78
220n
+ 100u
+
47u 220n
TDA7421
10
RFVcc
10
PLLVcc
10
OSCVcc
10
IF1Vcc & IF2 Vcc
L78L05A
Ground path
+5V
220n
Notes:
- The components shown on the evaluation board schematic without the part value, are required only
for measurements between intermediate input/outputs:
- Parts description:
CF1
CF3-CF4
CF2
T1
T2
T3
L2
L6
Ceramic filter 10.7MHz, 180KHz BW
Ceramic filter 10.7MHz, 150KHz BW
Ceramic filter 450KHz, 6KHz BW
FM RF transformer
Unloaded Q= 103
3-1= 3 1/2T - 6-4= 1T 0.12φ2UEW
CTUNING(3-1)= 24pF @ 100MHz
AM/FM IF1 transformer
Unloaded Q= 70
1-3= 13T - 1-5= 6 1/2T - 5-3= 6 1/2T - 4-6= 2T 0.08φ2UEW
CINT(1-2) = CINT(2-3) = 82pF; CEXT(1-3) = 10pF
AM IF2 transformer
Unloaded Q= 40
1-3= 178T - 1-2= 89T - 2-3= 89T - 4-6= 33T 0.05φ2UEW
CINT(1-3) = 180pF; CEXT(1-3) = 20pF
Oscillator coil
Unloaded Q= 80
6-4= 2 1/2T 0.12φ2UEW
CTUNING(6-4)= 36.8pF @ 100MHz
Demodulator Coil
Unloaded Q= 35
6-4= 27T 0.1φ2UEW
CINT(4-6)= 47pF; CEXT(4-6) = 13.5pF
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