TDA5220 Datasheet, PDF (25/44 Pages) Infineon Technologies AG – ASK/FSK Single Conversion Receiver

confidential
TDA 5220
preliminary
Applications
4.3 Quartz Load Capacitance Calculation
The value of the capacitor necessary to achieve that the quartz oscillator is
operating at the intended frequency is determined by the reactive part of the
negative resistance of the oscillator circuit as shown in Section 5.1.3 and by the
quartz specifications given by the quartz manufacturer.
Crystal
C_S
Input
impedance
Z_1-28
Pin 28
TDA5220
Pin 1
Figure 4-4
Quartz_load.wmf
Determination of Series Capacitance Value for the Quartz Oscillator
Crystal specified with load capacitance
C_S
=
1
C_l
1
+ 2π
f
X_L
with C_l the load capacitance (refer to the quartz crystal specification).
Example:
13.4 MHz: C_L = 12 pFX_L=1010 ΩC_S = 5.9 pF
This value may be obtained in high accuracy by putting two capacitors in series
to the quartz, such as 22pF and 8.2pF for 13.4MHz.
Wireless Components
4-5
Target Specification, October 2001