tda5255e1 Infineon Technologies Corporation, tda5255e1 Datasheet - Page 58

• Manufacturer Part Number: tda5255e1
• Description: Ask/fsk 434mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
In case of internal tuning: The crystal on the evaluation board has a temperature stability of +/-
20ppm (or +/- 8.7kHz), which must be added to the total tolerances in worst case. It’s possible to
choose a crystal compensating the oscillators temperature drift in a certain range and thus the
overall temperature tolerances are minimized.
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 +/- 8.7kHz) and a tuning tolerance of +/- 10ppm (or +/- 4.4 kHz). The external capacitors
add a tolerance of +/- 3.5ppm (or +/- 1.5kHz). Here also the overall temperature tolerances can be
reduced when applying an appropriate temperature drift of the crystal.
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
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
Preliminary Specification
D3
0
0
0
0
1
1
1
1
IQ-Filter
D2
0
0
1
1
0
0
1
1
3dB cutoff frequencies I/Q Filter
D1
0
1
0
1
0
1
0
1
nominal f
(programmable)
150 (default)
not used
not used
350
250
200
100
58
50
-3dB
in kHz
resulting effective
bandwidth in kHz
channel
700
500
400
300
200
100
TDA5255 E1
Version 1.1
Application
2002-11-28