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Nexxim Simulator >
Nexxim Component Models >
Lumped Elements General >
Crystal, Q, Parallel Resonance

Crystal, Q, Parallel Resonance

Netlist Form

An instance of an crystal , Q specified, parallel resonance, has the following Nexxim netlist syntax:

Axxx n1 n2 C=val FP=val [Q=val] [CO=val] [CL=val] [TC=val]
[MODE=val] [TEMP=val] [F1=val] [F2=val] COMPONENT=crystalqp

n1 and n2 are the nodes connected to the crystal. The entry COMPONENT=crystalqp identifies the element.

**Crystal, Q, Parallel Resonance Instance Parameters**
Parameter	Description	Units	Default
C	Motional capacitance	Farad	0.0
FP	Parallel overtone frequency	Hz	0.0
CO	Static capacitance	Farad	0.0
CL	Load capacitance	Farad	0.0
Q	Quality factor at resonant frequency FP	None	0.0
MODE	Overtone (odd number)	None	1
TC	Temperature coeffficient in PPM	None	0.0
TEMP	Device temperature	Celsius	25.0
F1	Lower resonant frequency limit	Hz	10
F2	Upper resonant frequency limit	Hz	1e12

Netlist Example

Acryqp1 port1 port2 C=9.5e-27 FP=27e6 CO=2.3e-12 CL=1.8e-11
+ Q=83000 F1=25e6 F2=75e6 COMPONENT=crystalqp

Notes

1. ESR is the equivalent series resistance for the crystal and can be calculated from Q factor (specified at resonant frequency FP) and the motional capacitance C as

ESR=1.0/(2π∗FP*Q*C).

2. L is the crystal’s motional inductance and can be calculated from motional capacitance C and resonant frequency FP.

3. F1 and F2 specify the frequency range for crystal device. The motional capacitance and the Q of the crystal will fall in the manufacture specified value in this frequency range.

4. TC is defined in PPM (parts per million). For example, a crystal has nominal value of FP at 298 K. At temperature TEMP, the resulting value of the series-self resonance frequency, F_p, is calculated as
F_p = FP*[1+(TEMP-298)*TC*1.0e-6]

5. MODE is used to specify the crystal’s overtone mode and must be an odd positive integer. Setting MODE to a value greater than 1 results in series self-resonances at FP and at FP/MODE. For example, setting FP equal to 222MHz and MODE equal to 5 results in series resonances at 222 MHz (the fifth-overtone resonance) and 222/5 MHz, or 44.4 MHz (the fundamental resonance).

6. The load capacitance, CL, is an external capacitance that sets a point on the reactance curve at which the crystal will resonate. CL comprises a combination of the circuit’s discrete load capacitance, stray board capacitance, and capacitance from the operation of the Miller effect in active devices. When an oscillator presents some amount of load capacitance to a crystal, the crystal is said to be parallel-resonant, and a value of load capacitance, CL, must be specified. If the circuit does not exhibit capacitive loading, the crystal is said to be series-resonant, and no value of load capacitance is specified. A quartz crystal’s parallel-resonance operating frequency FL is based on:

where FP is the series-resonance frequency, CL is the crystal load capacitance, CO is the crystal shunt capacitance, and C is the crystal motional capacitance.

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