TDA5251F1 Datasheet, PDF (47/88 Pages) Infineon Technologies AG – ASK/FSK 315MHz Wireless Transceiver

TDA5251 F1
Version 1.0
Confidential
Application
3.2
Crystal Oscillator
The equivalent schematic of the crystal with its parameters specified by the crystal manufacturer
can be taken from the subsequent figure.
Here also the load capacitance of the crystal CL, which the crystal wants to see in order to oscillate
at the desired frequency, can be seen.
L₁
C₁ R₁
C_L
-R
C₀
Figure 3-12
Crystal
L₁:
C₁:
C₀:
motional inductance of the crystal
motional capacitance of the crystal
shunt capacitance of the crystal
Therefore the Resonant Frequency f_s of the crystal is defined as:
1
f _S = _{2p L1 * C1}
[3 – 13]
The Series Load Resonant Frequency f_S‘ of the crystal is defined as:
Crystal.wmf
f_S `= _2p
1
*
L₁ * C₁
1+ ^C1
C₀ + C_L
regarding Figure 3-12
[3 – 14]
f_s’ is the nominal frequency of the crystal with a specified load when tested by the crystal
manufacturer.
Pulling Sensitivity of the crystal is defined as the magnitude of the relative change in frequency
relating to the variation of the load capacitor.
Preliminary Specification
47
2003-02-18