TDA7540N Datasheet, PDF (73/76 Pages) STMicroelectronics – AM/FM car radio tuner IC with stereo decoder and intelligent selectivity system (ISS)

TDA7540N
9
Application notes
Application notes
Following items are important to get highest performance of TDA7540N in application:
1. In order to avoid leakage current from PLL loop filter input to ground a guardring is
recommended around loop filter PIN’s with PLL reference (VREF2) voltage potential.
2. Distance between Xtal and VCO input PIN 18 should be far as possible and Xtal
package should get a shield versus ground.
3. Blocking of VCO supply should be near at PIN 20 and PIN 21.
4. Blocking of VCC2 supply should be near at PIN 64 and PIN 61.
5. Wire lenght to FM mixer1-input and -output should be symetrically and short.
6. FM demodulator capacitance at PIN 56 should be sense connected as short as
possible versus demodulator ground at PIN 57.
7. Wire lenght from AM mixer tank output to 9KHz ceramic filter input has to be short as
possible.
8. To minimize “AM TWEET” the AM demodulator capacitor should be connected versus
GNDVCC1 at PIN 41 and FSU output at PIN 22 should be filtered with capacitor of
about 2,2nF versus GNDVCC2.
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