TDA5200_10 Datasheet, PDF (25/39 Pages) Infineon Technologies AG – ASK Single Conversion Receiver

TDA 5200
ASK Single Conversion Receiver
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 Chapter 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 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 C_L the load capacitance (refer to the quartz crystal specification).
Examples
6.7 MHz
13.401 MHz
C_L = 12 pF
C_L = 12 pF
X_L = 750 Ω
X_L = 1250 Ω
C_S = 8.7 pF
C_S = 5.3 pF
These values may be obtained in high accuracy by putting two capacitors in series to the quartz, such as 20 pF
and 15 pF in the 6.7 MHz case and 15 pF and 8.2 pF in the 13.401 MHz case.
But please note that the calculated value of C_S includes the parasitic capacitors also.
Data Sheet
25
Revision 3.0, 2010-12-28