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SA-1100 Developer’s Manual C-3
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
——2 pF
Parasitic resistance between
TXTAL or TEXTAL to VSS
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.
Specification Minimum Typical Maximum Unit
Resonance frequency (fs) — 32768 — Hz
Quality factor (Q) 40K 80K 200K —
Motional capacitance (Cm) 234fF
Motional resistance (Rm) — — 50K W
Shunt capacitance (Co) 0.9 — 2 pF
Q1 Q2
Cm Lm Rm
Co