TDA5255E1 Datasheet, PDF (44/93 Pages) Infineon Technologies AG – ASK/FSK 434MHz Wireless Transceiver

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TDA5255 E1
Version 1.1
Application
pout_vs_frequ_434.wmf
Figure 3-8 Power output and collector current vs. frequency
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 (250Ohm@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 250Ohm+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 reference 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 TDA5255 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
Preliminary Specification
44
2002-11-28