TDA5251F1 View Datasheet(PDF) - Infineon Technologies

Part Name

Description

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TDA5251F1

ASK/FSK 315MHz Wireless Transceiver

Infineon Technologies 

TDA5251 F1

Version 1.1

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

CL

-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 fs of the crystal is defined as:

1

f S = 2π L1 * C1

[3 – 13]

The Series Load Resonant Frequency fS‘ of the crystal is defined as:

Crystal.wmf

fS `= 2π

1

*

L1 * C1

1+ C1

C0 + CL

regarding Figure 3-12

[3 – 14]

fs’ 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.

Data Sheet

47

2007-02-26

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