TDA5251F1_07 Datasheet, PDF (37/88 Pages) Infineon Technologies AG – ASK/FSK 315MHz Wireless Transceiver

3
3.1
3.1.1
Application
LNA and PA Matching
RX/TX Switch
TDA5251 F1
Version 1.1
Application
RX/TX_Switch.wmf
Figure 3-1 RX/TX Switch
The RX/TX-switch combines the PA-output and the LNA-input into a single 50 Ohm SMA-
connector. Two pin-diodes are used as switching elements. If no current flows through a pin diode,
it works as a high impedance for RF with very low capacitance. If the pin-diode is forward biased, it
provides a low impedance path for RF. (some Ω)
3.1.2 Switch in RX-Mode
The RX/TX-switch is set to the receive mode by either applying a high level or an open to the RX/
TX-jumper on the evalboard or by leaving it open. Then both pin-diodes are not biased and
therefore have a high impedance.
Data Sheet
37
2007-02-26