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SA-1110 Developer’s Manual 439
32.768–KHz Oscillator Specifications
C.1.2 Quartz Crystal Specification
The following specifications for the quartz crystal are shown in the figure and table below.
Parasitic capacitance off-chip
between TXTAL or TEXTAL and VSS
——2pF
Parasitic resistance between
TXTALorTEXTAL toVSS
10 ——MΩ
Parasitic resistance between
TXTAL and TEXTAL
10 ——MΩ
Resonance Frequency (fs): Resonance frequency of the crystal.
Motional Capacitance (Cm): Equivalent serial capacitance in the crystal model.
Motional Inductance (Lm): Not generally given in supplier specification.
Motional Resistance (Rm):
Equivalent serial resistance in the crystal model. Some crystal
providers refer to this resistance as the Equivalent Series
Resistance (ESR) or simply Series Resistance.
Other providers supply a Quality Factor, Q, instead of Rm;
therefore, the values for Q
corresponding to specified range of Rm are supplied in the
following table.
Shunt Capacitance (Co): Parasitic capacitance between Q1 and Q2.
Load Capacitance (CL): Needed load capacitance viewed by the crystal to oscillate at fs.
Drive Level: Power dissipated in the equivalent serial resistance (Rm).
Aging: Resonance frequency shift due to aging.
Q1 Q2
Cm Lm Rm
Co