Those who tell is a bit more straightaway, will compare with a joke that once had heard, probably the meaning is this plane is hijacked by me, other hijacker waits next time. This capacitance is hijacker.

 

Brilliant brace up circuit is a capacitance actually at 3 o’clock type oscillating circuit, output is equivalent of Zheng Xuanbo crystal at inductance, add cent of two chamfer road to control electric capacity, the electric capacity that inputs end is smaller, amount of make a present of of positive and negative is larger. Laden capacitance every brilliant brace up metropolis some parameter, for example stability is how many PPM, partial person can say for frequency difference, the unit is PPM, laden capacitance is how many PF. When brilliant brace up the capacitance that receives concussion circuit to go up to introduce in concussion circuit place does not accord with brilliant brace up the frequency that place of circuit of the concussion when the capacity of laden capacitance asks gives is met the frequency of bid of He Jingzhen place is different

 

 

Again illustrate:

 

The brilliant that laden capacitance of a 4.0000MHz +-20PPM is 16PF brace up;

 

When laden capacitance it is place of circuit of the concussion when 10PF the frequency that give may be 4.0003MHz;

 

When laden capacitance it is place of circuit of the concussion when 20PF the frequency that give may be 3.9997MHz;

 

What ask to PLL is like on tall circuit in precision of a few pairs of frequency is fiducial wait. . . Namely and many adjustable capacitance comes to what small frequency modulation leads;

 

If ask to used fixed capacitance not high to go to frequency precision;

 

Brilliant brace up laden capacitance has 2 kinds to receive a standard commonly 1 paralell connection is in brilliant brace up on 2 series connection are in brilliant brace up on;

 

The 2nd kind more commonly used 2 feet receive a capacitance to exchanging the land.

 

The laden capacitance of crystal component is to point to in crystal of the bond in circuit the total external world of two end is effective capacitance. It is to point to brilliant brace up the capacitance that wants need of normal concussion place. General outside receive capacitance, it is to make brilliant brace up the equivalent capacitance of two end is equal to or approach laden electric capacity. The right capacitance that asks tall circumstance considers Ic to input end even. Be in commonly when application give out adjust near laden capacitance value can get accurate frequency. The size of this capacitance basically affects laden and syntonic frequency and resistor of equivalent and laden resonance.

 

Brilliant brace up the Cd in type of C of △ of laden capacitance =[(Cd*Cg)/(Cd+Cg)]+Cic+ , cg is in to be received respectively brilliant brace up mix on two feet the capacitance to the ground, cic (capacitance of integrated circuit interior) + △ C () of the capacitance on PCB. The word of 15pf of capacitance of load of that is to say, both sides those who receive 27pf is about the same, general A is 6.5 ～ 13.5pF

 

The brilliant of all sorts of logistic chip brace up it is OK to cite a base equivalent is capacitance at 3 o’clock type oscillator. Brilliant brace up the interior that cites a base is an inverter normally, odd perhaps an inverter series connection. In brilliant brace up output brings crural XO He Jingzhen to input join with a resistor between the XI that cite a base, to CMOS chip it is several M normally arrive between tens of M Europe. The interior citing a base of a lot of chip had included this resistance, cite a base exterior need not receive. This resistor is to make inverter is when oscillation is initiative place and linear condition, inverter has the amplifier of very big gain as, rise in order to facilitate brace up. Quartz crystal also joins in brilliant brace up between the input that cites a base and output, equivalent is a shunt-wound and syntonic loop, oscillation frequency should be quartz the shunt-wound and syntonic frequency of crystal. The two capacitance ground connection on the side of crystal, it is capacitance actually the cent of type circuit controlled electric capacity at 3 o’clock, ground connection is nodded even if cent controls an aspect. Press a dot to be reference point with receiving a place to be divided namely, the input that oscillation cites a base and output are in opposition, but from shunt-wound and syntonic loop namely quartz crystal in light of two end, form make a present of of a positive and negative to last in order to assure circuit oscillation. When chip is designed, these two capacitance had been formed, it is two capacity commonly equal, capacity size depends on craft and domain and differ, but eventually is smaller, do not suit very wide frequency range certainly. Several PF are about when be being received outside to tens of P, according to frequency and quartz of crystal characteristic and calm. Those who need an attention is: The value that these two capacitance establish ties is shunt-wound on syntonic loop, can affect oscillation frequency. When two capacitance are equal, feedback coefficient is 0.5, can satisfy oscillation requirement commonly, but if rise not easily brace up or oscillation is not stable and OK reduce an input to carry right capacitance, and the cost that raises output end is measured with raising feedback.

 

The design considers matter:

 

1. makes brilliant brace up, exterior capacitor (if have) keep the shortest as far as possible with the line between IC. Through IC brilliant when low-down electric current Zhen Zhen swings implement when, if line is too long, can make it right EMC, ESD and the influence with the very sensitive generation that string together faze. And long line still can increase parasitism electric capacity to the oscillator.

 

2. arranges the line route of other clock circuitry and frequent switch as far as possible in be far from brilliant brace up connective position.

 

3. is careful brilliant brace up with the ground take a line

 

4. general brilliant brace up crust ground connection

 

If actual laden capacitance configuration is undeserved, the error that causes circuit reference frequency a little while. If blasting off,receive the meeting on circuit to make additionally brilliant brace up oscillation extent drops (do not nod) in the peak, affect the signal intensity of mixing signal and letter a confusion of voices.

 

Appear when weaveform cut a peak, when distortion, can increase laden resistor to adjust (a few K arrive hundreds of K) , wanting stable weaveform is shunt-wound the feedback resistor that a 1M controls.