tda5255e1 Infineon Technologies Corporation, tda5255e1 Datasheet - Page 53

• Manufacturer Part Number: tda5255e1
• Description: Ask/fsk 434mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
In receive mode the crystal oscillator frequency is set to yield a direct-to-zero conversion of the
receive data. Thus the frequency may be calculated as
e.g.
which is identical to the ASK transmit case.
Figure 3-18
In this case the ASK-switch is closed. The necessary C
The C-bank C
receive frequency. In this case the switches of the C-bank are controlled by the bits D0 to D5 of the
XTAL_TUNING register (subaddress 02H, see Table 3-5).
3.2.2.2
In transmit mode the crystal oscillator frequency is the same as in the FSK receive case, see
Figure 3-18.
In receive mode a receive frequency offset is necessary as the limiters feedback is AC-coupled.
This offset is achieved by setting the oscillator frequency to the FSK HIGH transmit frequency, see
Figure 3-17.
3.2.3
For the correct calculation of the external capacitors the parasitic capacitances of the pins and the
switches (C
Preliminary Specification
20
C vm
ASK-mode:
Parasitics
f
f
, C
tune2
COSC
COSC
FSK receive
21
=
, C
can be varied over a range of 16 pF in steps of 250fF for finetuning of the FSK
(
------------------------------------------------------------------------------------------------------- -
= f
= 434,16E6 / 24= 18.09MHz
C
C v1
22
v1
RF
) have to be taken into account.
+
+
/ 24,
C
C tune1
tune1
C
C
V1
V2
)
C
+
f, C
×
V3
(
C v2
C
L
v2
XSWA 22
XOUT 19
XSWF 20
XGND 23
XIN 21
+
+
C
C
v3
v3
+
+
C tune2
C
53
L
tune2
)
vm
-R
is given by:
C
C
tune2
tune1
[3 – 22]
[3 – 23]
TDA5255 E1
Version 1.1
Application
2002-11-28
QOSC_ASK.wmf