tda5251f1 Infineon Technologies Corporation, tda5251f1 Datasheet - Page 53

• Manufacturer Part Number: tda5251f1
• Description: Ask/fsk 315mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
3.2.3
For the correct calculation of the external capacitors the parasitic capacitances of the pins and the
switches (C
Figure 3-17
Table 3-2
With the given parasitics the actual C
Note: Please keep in mind also to include the Pad parasitics of the circuit board.
Preliminary Specification
C vm
C v+
20
=
Name
Parasitics
C 20
C 21
C 22
, C
(
---------------------------------------------------------------------------------------------------------------------------------------- -
Typical values of parasitic capacitances
C v1
=
C
parasitics of the switching network
v1
21
(
-------------------------------------------------------------------------------------------------------
C v1
C v1
, C
+
+
C tune1
C
22
C
+
tune1
+
v-
) have to be taken into account.
C tune1
C
C
C tune1
V1
V2
=
)
+
×
C
(
C
v1
C v2
)
v2
C
f, C
+
×
V3
+
(
C v2
C v2
+
L
C
+
C
tune1
C 20
XSWA 22
XSWF 20
XOUT 19
XGND 23
20
+
+
v
XIN 21
C 20
can be calculated:
C 20
+
+
C
+
C
FSK-: 2,8 pF / FSK+&ASK: 2.2pF
v3
C
+
v3
+
21
C
C
+
+
tune2
tune2
C
C 22
22
53
C
22
L
+
+
)
C
C
+
tune2
C
tune2
C 21
4,6 pF
21
Value
1 pF
-R
)
C
+
20
C 21
C
C
tune2
tune1
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TDA5251 F1
Version 1.0
QOSC_parasitics.wmf
Application
2003-02-18