TDA5250D2 Datasheet, PDF (49/97 Pages) Infineon Technologies AG – ASK/FSK 868MHz Wireless Transceiver

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TDA 5250 D2
preliminary
Applications
C4, L2 and C3||C2 are the main matching components which are used to
transform the 50 Ohm load at the SMA-RF-connector to a higher impedance at
the PA-output (240Ohm@3V). L1 can be used for finetuning of the resonance
frequency but should not be too low in order to keep its loss low.
The transformed impedance of 240Ohm+j0 at the PA-output-pin can be verified
with a network analyzer using this measurement procedure:
1. Calibrate your network analyzer.
2. Connect a short, low-loss 50 Ohm cable to your network analyzer with an
open end on one side. Semirigid cable works best.
3. Use the „Port Extension“ feature of your network analyzer to shift the refer-
ence plane of your network analyzer to the open end of the cable.
4. Connect the center-conductor of the cable to the solder pad of the pin „PA“
of the IC. The shield has to be grounded. Very short connections must be
used. Do not remove the IC or any part of the matching-components!
5. Screw a 50Ohm-dummy-load on the RF-I/O-SMA-connector
6. The TDA5250 has to be in ASK-TX-Mode, Data-Input=LOW.
7. Be sure that your network analyzer is AC-coupled and turn on the power
supply of the IC.
8. Measure the S-parameter
Figure 4-9 Sparam_measured_200M
Wireless Components
4-9
Sparam_measured_200M.pcx
Specification, July 2002