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<strong>TDA7200</strong><br />
Applications<br />
asymmetrical offset for the demodulation of long zeros the lower of the two FSK<br />
frequencies should be chosen in the transmitter as the zero-symbol frequency.<br />
In the following figure the shape of the above mentioned bandpass is shown.<br />
gain (pin19)<br />
v<br />
v-3dB<br />
20dB/dec<br />
-40dB/dec<br />
3dB<br />
0dB<br />
DC<br />
f1 f2 f3<br />
f<br />
0.18mV/kHz<br />
2mV/kHz<br />
Figure 10 Frequency characteristic in case of FSK mode<br />
The cutoff frequencies are calculated with the following formulas:<br />
f<br />
1<br />
1<br />
=<br />
R1×<br />
330kΩ<br />
2π<br />
× C13<br />
R1<br />
+ 330kΩ<br />
f ×<br />
2 = v×<br />
f1<br />
= 11 f1<br />
f3 = f3dB<br />
f 3 is the 3dB cutoff frequency of the data filter - see Section 3.2.<br />
Example:<br />
R1 = 100kΩ, C13 = 47nF<br />
This leads tof 1 = 44Hz and f 2 = 485Hz<br />
Data Sheet 27 V 1.0, 2007-05-02
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