TDA5250D2 Datasheet, PDF (61/97 Pages) Infineon Technologies AG – ASK/FSK 868MHz Wireless Transceiver

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TDA 5250 D2
preliminary
Applications
To compensate frequency errors due to crystal and component tolerance C_v1,
C_v2 and C_v3 have to be varied. To enable this correction, half of the necessary
capacitance variation has to be realized with the internal C-banks.
If no finetuning is intended it is recommended to leave XIN (Pin 21) open. So
the parasitic capacitance of Pin 21 has no effect.
Note: Please keep in mind also to include the Pad parasitics of the circuit board.
In the suitable range for the serial capacitor, either capacitors with a tolerance
of 0.1pF or 1% are available.
A spreadsheet, which can be used to predict the total frequency error by simply
entering the crystal specification, may be obtained from Infineon.
4.2.5 FSK-switch modes
The FSK-switch can be used either in a bipolar or in a FET mode. The mode of
this switch is controlled by bit D0 of the XTAL_CONFIG register (subaddress
0EH).
In the bipolar mode the FSK-switch can be controlled by a ramp function. This
ramp function is set by the bits D1 and D2 of the XTAL_CONFIG register
(subadress 0EH). With these modes of the FSK-switch the bandwidth of the
FSK spectrum can be influenced.
When working in the FET mode the power consumption can be reduced by
about 200 µA.
The default mode is bipolar switch with no ramp function (D0 = 1, D1 = D2 = 0),
which is suitable for all bitrates.
Table 4-3 Sub Address 0EH: XTAL_CONFIG
D0 D1 D2
Switch mode
Ramp time
0 n.a. n.a.
FET
< 0.2 µs
1
0
0 bipolar (default)
< 0.2 µs
1
1
0
bipolar
4 µs
1
0
1
bipolar
8 µs
1
1
1
bipolar
12 µs
Max. Bitrate
> 32 kBit/s NRZ
> 32 kBit/s NRZ
32 kBit/s NRZ
16 kBit/s NRZ
12 kBit/s NRZ
Wireless Components
4 - 21
Specification, July 2002