TDA5250D2_07 Datasheet, PDF (60/94 Pages) Infineon Technologies AG – ASK/FSK 868MHz Wireless Transceiver

TDA5250 D2
Version 1.7
Application
Concerning the frequency tolerances of the whole system also crystal tolerances (tuning
tolerances, temperature stability, tolerance of CL) have to be considered.
In addition to the chip tolerances also the crystal and external component tolerances have to be
considered in the tuning and non-tuning case.
In case of internal tuning: The crystal on the evaluation board has a temperature stability of +/-
20ppm (or +/- 17kHz), which must be added to the total tolerances.
In case of default setup (without internal tuning and without usage of pin 21) the temperature
stability and tuning tolerance of the crystal as well as the tolerance of the external capacitors (+/-
0.1pF) have to be added. The crystal on the evaluation board has a temperature stability of +/-
20ppm (or +/- 17kHz) and a tuning tolerance of +/- 10ppm (or +/- 8.5 kHz).The external capacitors
add a tolerance of +/- 4ppm (or +/- 3.5kHz).
The frequency stabilities of both the receiver and the transmitter and the modulation bandwidth set
the limit for the bandwidth of the IQ filter. To achieve a high receiver sensitivity and efficient
suppression of adjacent interference signals, the narrowest possible IQ bandwidth should be
realized (see Section 3.3).
3.3
IQ-Filter
The IQ-Filter should be set to values corresponding to the RF-bandwidth of the received RF signal
via the D1 to D3 bits of the LPF register (subaddress 03H).
Table 3-9
D3
3dB cutoff frequencies I/Q Filter
D2
D1
nominal f_-3dB in kHz
(programmable)
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
not used
350
250
200
150 (default)
100
50
not used
resulting effective
channel
bandwidth in kHz
700
500
400
300
200
100
Data Sheet
60
2007-02-26