TDA7210V_10 Datasheet, PDF (20/44 Pages) Infineon Technologies AG – ASK/FSK Single Conversion Receiver

TDA7210V
Applications
3.3
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 Chapter 4.1.3 and
by the quartz specifications given by the quartz manufacturer.
Crystal
C_S
Input
impedance
Z_30-28
Pin 30
TDA7210V
Pin 28
Figure 8 Determination of Series Capacitance Value for the Quartz Oscillator
Crystal specified with load capacitance
C_S
=
1
C_L
1
+ 2π
f
X_L
(4)
with CL the load capacitance (refer to the quartz crystal specification).
Examples
6.7 MHz: CL = 12 pF, XL=695 Ω, CS = 8.9 pF
13.4 MHz: CL = 12 pF, XL=1010 Ω, CS = 5.9 pF
These values may be obtained in high accuracy by putting two capacitors in series to the quartz, such as 22 pF
and 15 pF in the 6.7 MHz case and 22 pF and 8.2 pF in the 13.4 MHz case.
But please note that the calculated value of CS includes the parasitic capacitors also.
Data Sheet
20
Revision 1.1, 2010-06-18