TDA5255E1_07 Datasheet, PDF (52/91 Pages) Infineon Technologies AG – ASK/FSK 434MHz Wireless Transceiver

TDA5255 E1
Version 1.2
Application
e.g.
f_{COSC HI}
= (434,16E6 + 35E3) / 24= 18.09146MHz
f_{COSC LOW} = (434,16E6 - 35E3) / 24= 18.08854MHz
with a frequency deviation of 35kHz.
Figure 3-17 shows the configuration of the switches and the capacitors to achieve the 2 desired
frequencies. Gray parts of the schematics indicate inactive parts. For FSK modulation the ASK-
switch is always open.
For FSK LOW the FSK-switch is closed and C_v2 and C_tune2 are bypassed. The effective C_v- is given
by:
C_{V −} = C_v1 + C_tune1
[3 – 20]
For finetuning Ctune1 can be varied over a range of 8 pF in steps of 125fF. The switches of this C-
bank are controlled by the bits D0 to D5 in the FSK register (subaddress 01H, see Table 3-6).
For FSK HIGH the FSK-switch is open. So the effective C_v+ is given by:
Cv+
=
-⁽--C----v----1----+-----C----t--u----n---e---1----⁾---^â‹---⁽---C----v----2----+-----C----t--u----n---e---2----⁾
Cv1 + Ctune1 + Cv2 + Ctune2
[3 – 21]
The C-bank Ctune2 can be varied over a range of 16 pF in steps of 250fF for finetuning of the FSK
HIGH frequency. The switches of this C-bank are controlled by the bits D8 to D13 in the FSK
register (subaddress 01H, see Table 3-6).
XOUT 19
L
f, C_L
XIN 21
C_V1
XSWF 20
XSWA 22
C_V2
C_V3
XGND 23
-R
C_tune1
C_tune2
XOUT 19
L
f, C_L
XIN 21
C_V1
XSWF 20
XSWA 22
C_V2
C_V3
XGND 23
-R
C_tune1
C_tune2
FSK LOW
Figure 3-17 FSK modulation
Data Sheet
52
FSK HIGH
QOSC_FSK.wmf
2007-02-26