TDA5250D2_07 Datasheet, PDF (39/94 Pages) Infineon Technologies AG – ASK/FSK 868MHz Wireless Transceiver

3
3.1
3.1.1
Application
LNA and PA Matching
RX/TX Switch
TDA5250 D2
Version 1.7
Application
RF I/O
C1
50 Ohm
SMA-connector
C2
VCC
C5
L1
D1
L2
PA
C3
C4
R1
C7
C9
D2
RX/TX
C6
L3 ^C10
LNI
LNIX
RX/TX
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
39
2007-02-26