tda5251f1 Infineon Technologies Corporation, tda5251f1 Datasheet - Page 50

• Manufacturer Part Number: tda5251f1
• Description: Ask/fsk 315mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
With C
Alternatively, an external AC coupled (10nF in series to 1k
The drive level should be approximately 100mVpp.
3.2.1
Generating ASK and FSK modulation 3 setable frequencies are necessary.
3.2.1.1
The resulting possible crystal oscillator frequencies are shown in the following Figure 3-14
Figure 3-14
In ASK receive mode the crystal oscillator is set to frequency f
offset to receive the ASK signal at f
To set the 3 different frequencies 3 different C
capacitors can be combined to generate the necessary C
Internal banks of switchable capacitors allow the finetuning of these frequencies.
3.2.2
Depending on whether the device operates in transmit or receive mode or whether it operates in
ASK or FSK the following cases can be distinguished:
3.2.2.1
In transmit mode the two frequencies representing logical HIGH and LOW data states have to be
adjusted depending on the intended frequency deviation and separately according to the following
formulas:
f
Preliminary Specification
COSC HI
L+
= (f
and C
RF
Synthesizer Frequency setting
Possible crystal oscillator frequencies
Transmit/Receive ASK/FSK Frequency Assignment
FSK-mode
+ f
L-
possible crystal oscillator frequencies
the necessary C
DEV
) / 24
RX:
TX:
FSK-
f
1
v+
Deviation
f
0
COSC LOW
*N (N: division ratio of the PLL).
for FSK HIGH and C
Frequency
Nominal
FSK
ASK
f
0
Deviation
= (f
50
v
RF
are necessary. Via internal switches 3 external
ASK
FSK+
- f
f
2
DEV
W
v-
) / 24
) signal can be applied at pin 19 (Xout).
v
for FSK LOW can be calculated.
in case of ASK- or FSK-modulation.
2
to realize the necessary frequency
[3 – 19]
TDA5251 F1
Version 1.0
Application
2003-02-18
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