Contents
What is external crystal oscillator?
Many microcontroller applications require a timing source more accurate than the typical internal oscillator. An external crystal can provide a solution. These crystals are used with an external crystal oscillator (ECO) to generate clocks as accurate as ±50 parts per million.
What is the frequency of the external oscillator crystal?
Typical crystal oscillators can range in oscillation frequencies from about 40kHz to well over 100MHz depending upon their circuit configuration and the amplifying device used.
How is crystal oscillator measured?
Bring the measurement probes of the multimeter into contact with the metallic legs of the crystal oscillator. One probe should touch each leg. The multimeter should now read a frequency that corresponds to the one written on the crystal oscillator casing.
What is the value of crystal oscillator?
The maximum Q for a high stability quartz oscillator can be estimated as Q = 1.6 × 107/f, where f is the resonant frequency in megahertz. One of the most important traits of quartz crystal oscillators is that they can exhibit very low phase noise.
How is the transconductance of an oscillator important?
Oscillator Transconductance Another way to consider if the oscillator will start up consistently is to consider the transconductance. To ensure oscillation starts and reaches a stable phase, the oscillator must provide enough gain to compensate for the oscillation loop losses and to provide the energy for the oscillation build up.
What are the parameters of a STM32 crystal oscillator?
They are the parameters of the STM32 built-in oscillator, namely transconductance, and the critical limit the crystal circuit must not require for good operation. That is why you can’t find crystals with those parameters.
How is a parallel resonant oscillator circuit designed?
A parallel resonant Oscillator circuit uses a Crystal unit which is designed to operate with a specific value of load capacitance. This will create an outcome in which a Crystal frequency with is higher than the series resonant frequency, but lower than the true parallel resonant frequency.
How is a crystal pulled from its series frequency?
A crystal can be “pulled” from its series frequency by adding reactance (capacitance) in series with the crystal. When operated in combination with an external load capacitance (CL) the crystal oscillates in a frequency range slightly above its series resonant frequency. This is the parallel (load resonant) frequency.