TDA 5210
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.
CS
Pin 28
Input
impedance
Crystal
Z1-28
TDA5210
Pin 1
Quartz_load.wmf
Figure 4-4
Determination of Series Capacitance Value for the Quartz Oscillator
Crystal specified with load capacitance
1
CS =
1
+ 2π f X L
Cl
with Cl the load capacitance (refer to the quartz crystal specification).
Examples:
6.7 MHz: CL = 12 pFXL=695ΩCS = 8.9 pF
13.4 MHz: CL = 12 pFXL=1010 ΩCS = 5.9 pF
These values may be obtained in high accuracy by putting two capacitors in
series to the quartz, such as 22pF and 15pF in the 6.7MHz case and 22pF and
8.2pF in the 13.4MHz case.
Wireless Components
4 - 5
Specification, May 2001