Application of quartz crystal in the computer motherboard

The quartz crystal oscillator is called crystal resonator, referred to as the crystal. The computer motherboard is generally rectangular board, there are a variety of chip oscillator and clock generator. The clock chip composed of the main board, most of the components on the motherboard, providing the signal from the clock generator, clock generator is the core of the motherboard clock circuit, as the heart of the motherboard motherboard. The main crystal clock oscillator, crystal oscillator and real-time sound card, NIC crystal.

1,Clock oscillator

Clock oscillator and clock produce circuit are connected, frequency of 14.318MHz, the crystal damage, will cause the motherboard failure cannot be started. During normal operation, the voltage between the two pin 1-6V

2, the sound of crystal

Sound card and sound card chip is connected with the oscillator, the oscillator frequency is 24.576 MHz, after the damage, will cause the sound deterioration or silent fault. When in normal work, two pins of the voltage is 1-2.1V.

3, NIC crystal

NIC crystal and NIC chip frequency is 25 MHz, the oscillator is damaged, will cause the fault network function work. During normal operation, the voltage between two pin 1.1-2.1V.

4, real-time crystal

Real time crystal and the Southbridge chip frequency is 32 768kHz, the oscillator is damaged, will cause the fault time correct or cannot be started. During normal operation, the voltage between the two pins of the 0.5V.

Many people will be asked to board above the crystal in the end is what effect to have? The computer motherboard will generally have 2-3 quartz crystal, very simple that computer motherboard crystal is used to control the time of the application, the computer has a timing circuit, call timer.

Computer timer is usually a precision processed quartz crystal, quartz crystal in the tension within the limits to a certain frequency, the frequency depends on the crystal size and how to cut itself by tension. There are two registers associated with each quartz crystal oscillator, a holding register and a counter. Each time the quartz oscillation the crystal of the counter by 1 when the counter reaches 0, to generate an interrupt, keep the counter counter from reloads the initial value. This method makes the programming of a timer, to produce 60 times per second interruption (or in any other desired frequency interrupt) possible. Each interrupt is called a clock tick.

The crystal is equivalent to a capacitor and a resistor in parallel and series two terminal network of a capacitor in the electrical, electrical engineering on the network has two resonant frequency points, in which low frequency series resonance, high frequency parallel resonance. Due to the characteristics of the crystal itself in close is this the two frequency range, in this very narrow frequency range, the oscillator equivalent to a capacitor inductor, so as long as the crystal is connected in parallel with the appropriate it will form a parallel resonance circuit. The parallel resonant circuit to a negative feedback circuit can constitute a sine wave oscillation circuit, the oscillator is equivalent to inductance frequency The scope is very narrow, so even if the parameters of other components vary greatly, the frequency of the oscillator will not change much.

The crystal is an important parameter, which is the load capacitance value, select the parallel capacitor and the load capacitance is equal to the value, you can get the crystal resonant frequency. The nominal crystal oscillation circuit is generally in an inverting amplifier (note that it is not the end of the two phase inverter amplifier) access crystal, another two capacitors respectively at both ends a crystal, the other end of each capacitor connected to the ground, the two series capacitor capacity should be equal to the value of the load capacitance, please note that the IC pins have equivalent input capacitance, this can not be omitted.

The general crystal load capacitance is 15p or 12.5p, if we consider the equivalent input capacitance element pins, crystal oscillation circuit is two 22P capacitors is a good choice. The table method for measuring crystal oscillator is working with the measurement of two pin voltage is half chip voltage. For example, the operating voltage is 51 single-chip +5V is about 2.5V. And if the tweezers touch crystal another foot, the voltage changes obviously, that is starting up.

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