TDA5212 Datasheet, PDF (27/51 Pages) Infineon Technologies AG – ASK/FSK 915MHz Single Conversion Receiver

TDA 5212
preliminary
Applications
4.4 Crystal Frequency Calculation
The local oscillator (UHF PLL) signal has to be high-side injected into the down-
converting mixer. Thus the crystal frequency is calculated by using the following
formula:
ƒ_QU = (ƒ_RF + 10.7) / r
with
ƒ_RF .... receive frequency
ƒ_LO .... local oscillator (PLL) frequency (ƒ_RF + 10.7)
ƒ_QU .... crystal oscillator frequency
r .... ratio of local oscillator (PLL) frequency and crystal
frequency as shown in the subsequent table.
Table 4-1 PLL Division Ratio Dependence on States of CSEL
CSEL
Ratio r = (f_LO/f_QU)
open
128
GND
64
This yields the following example:
CSEL tied to GND:
f _QU = (915MHz + 10.7MHz ) / 64 = 14.4641 MHz
Wireless Components
4-6
Specification, May 2003