TDA5250D2_07 Datasheet, PDF (43/94 Pages) Infineon Technologies AG – ASK/FSK 868MHz Wireless Transceiver

TDA5250 D2
Version 1.7
Application
RF I/O
C1
50 Ohm
SMA-connector
C2
VCC
C5
L1
L2
PA
C3
C4
R1
grounded RX/TX
(with jumper or
RX/TX-pin of IC)
C7
C9
L3 ^C10
C6
LNI
LNIX
RX/TX
TX_Mode.wmf
Figure 3-4 TX_Mode
R1 does not influence the matching because of its very high resistance. Due to the large
capacitance of C1, C6 and C5 the circuit can be further simplified for RF:
RF I/O
50 Ohm
C2
SMA-connector
L1
L2
PA
C3
C4
C7
C9
L3 ^C10
LNI
LNIX
TX_Mode_simplified.wmf
Figure 3-5 TX_Mode_simplified
The LNA-matching is RF-grounded now, so no power is lost in the LNA-input. The PA-matching
consists of C2, C3 L2, C4 and L1.
When designing the matching of the PA, C2 must not be changed anymore because its value is
already fixed by the LNA-input-matching.
Data Sheet
43
2007-02-26