TDA7220 Datasheet, PDF (6/16 Pages) STMicroelectronics – VERY LOW VOLTAGE AM-FM RADIO

TDA7220
AM-FM SWITCHING
AM-FM switching is achieved by applying a DC voltage at pin 13, to switch the internal reference.
TYPICAL DC VOLTAGE (refer to the test circuit)
Pins 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Unit
AM 3 1.1 3 1.1 1.1 2.5 3 0.7 1.2 3 0 2.1 2.1 2.9 3 2.9 V
FM 3 0 3 0 0 2.4 3 0 0.9 3 0 3 3 2.7 2.7 2.7 V
APPLICATION SUGGESTION
Recommended values referred to the test circuit of Figure 1
Part
Number
C1
C2 (1)
C3 (1)
C4
C5
C7
C8
C9
C10 (1)
C11
C12
C13
C16
R1 (1)
R2 (1)
R3
R4
R5
R6
Recommended
Value
100µF
100nF
10nF
20nF
20nF
100nF
100nF
10µF
56pF
10nF
100nF
220µF
2.7nF
68Ω
56Ω
330Ω
6.8kΩ
560Ω
13kΩ
Purpose
AGC Bypass
AM Input DC Cut
FM Input DC Cut
FM Amplifier Bypass
FM detector Decoupling
Power Supply Bypass
AGC Bypass
Tuning of the AM
Oscillator at 1455kHz
50ms FM De-emphasis
Output DC Decoupling
Power Supply Decoupling
AM Detector capacitor
FM Input Matching
AM Input Matching
Ceramic Filter Matching
FM Detector Coil Q Setting
FM Detector Load Resistor
AM Detector Coil Q Setting
Smaller than
Recommended Value
Increase of the distortion at
low audio frequency
Reduction of sensitivity
Danger of RF Irradiation
Noise increase of the audio
output
Increase of the distortion at
low audio frequency
Low audio frequency cut
Increase of the distortion at
low frequency
Low suppression of the IF
frequency and harmonics
Audio output decrease and
lower distortion
Audio output decrease and
higher AMR
Lower IF Gain and Lower
AGC Range
Larger than
Recommended Value
Increase of the AGC time
constant
- bandwidth increase
- higher noise
Increase of the AGC time
constant
Increase of the audion
distortion
Audio output increase and
higher distortion
Higher IF Gain and Lower
AGC Range
(1) Only for test circuit.
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