TDA5201 Datasheet, PDF (25/43 Pages) Infineon Technologies AG – ASK Single Conversion Receiver

TDA 5201
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
TDA5200
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).
Examples:
5.1 MHz: C_L = 12 pF
10.18 MHz: C_L = 12 pF
X_L=580 Ω
X_L=870 Ω
C_S = 9.8 pF
C_S = 7.2 pF
These values may be obtained by putting two capacitors in series to the quartz,
such as 18pF and 22pF in the 5.1MHz case and 18pF and 12pF in the 10.2MHz
case.
But please note that the calculated value of C_S includes the parasitic capacitors
also.
Wireless Components
4-5
Specification, July 2004