Technical Guide

Types of crystal cut

Relation among crystal cut, mode of vibration and frequency range

Crystal Cut Mode of vibration Frequency range (kHz) Capacitance ratio
(C0/C1)
AT Thickness shear Fundamental 800~5,000
2,000~80,000
450~300
220
3rd overtone 20,000~90,000 n2 x 250
n: Overtone order
5rd overtone   40,000~150,000
7rd overtone   70,000~210,000
BT Thickness shear Fundamental Thickness shear Fundamental 3,000~30,000 650
XY Flexural (Tuning fork) 16~150 425~800
Extensional 600~3,000 400
DT Face shear 100~500 400
CT 150~850 350
SL 180~700 400

Crystal unit equivalent circuit

A crystal unit in the main resonance frequency may be expressed as an electrical equivalent circuit: a circuit ordinarily composed of a series circuit consisting of an inductance, capacitance and resistance, and a capacitance connected in parallel to the series circuit as shown in the drawing.


Here, C0, which is commonly known as the shunt capacitance, comprises an inter-electrode static capacitance to which the inter-terminal stray capacitance is added.


L1 and C1 are the equivalent constants of the crystal unit viewed as an electrical and mechanical oscillation system. Since both constants are determined by such factors as the type of cut, cutting angle, dimensions of the crystal blank, and construction of the electrodes, and are thus reproducible, crystal units can be manufactured with high precision.


R1, which denotes oscillation loss, is governed by conditions such as processing, storage, and dimensions of the crystal unit.


L1 is referred to as motional inductance, C1 is referred as motional capacitance, and R1 is referred as motional (series) resistance.


L1 Motional inductance
C1 Motional capacitance
R1 Motional(series)resistance
C0 Shunt capacitance

The electrical equivalent circuit, composed of L1, C1, R1 and C0, all of which are correlated, may be expressed by the following equation.

Shown below are some equations by which the performances of crystal units are expressed.

Frequency-temperature characteristics

Correlation between Crystal cutting angle and Frequency-temperature characteristics

Correlation between Crystal cut and Frequency vs. temperature characteristics

Frequency-temperature characteristics of Tuning Fork Crystal Unit

Frequency vs. temperature characteristic of Tuning Fork Crystal Unit

Correlation between Crystal cutting angle and Frequency-temperature characteristics of AT-cut Crystal Unit

Correlation between Crystal cutting angles and Frequency vs. temperature characteristics of AT-cut Crystal Units

Test Circuit

CSX-750F/SSX-750P SERIES


Current Consumption

*1

390Ω CSX-750(FC)
820Ω SSX-750(PT, PK)

CMOS load

CMOS load


*2

50pF CSX-750(FC)
30pF CSX-750(FB, FJ)
25pF SSX-750(PC, PD)
15pF SSX-750(PB, PJ), CSX-252F

Current Consumption

Current Consumption

Output wave-form

Oscillators output wave-form

CMOS load

TTL load

Measurement conditions

  • Oscilloscope ・Input impedance: No less than 1 MΩ ・Input capacitance: No more than 15 pF ・Band width: No less than 500 MHz ・Make the grounding lead of the probe as short as possible.
  • The CL includes the probe capacitance.
  • Grounding should be single-point grounding.
  • Supply voltage impedance should be as low as possible. Rise time from 0V to 0.9Vdd is to be more than 150 μs.
  • Use an ammeter with small internal impedance.