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——M
Parasitic resistance between
TXTAL and TEXTAL 10——M
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