Quartz crystal oscillator with spread spectrum output
Through the crystal chip design of quartz crystal oscillator and triangular wave modulation spread spectrum technology, the problem of excessive EMI radiation in the clock signal in digital circuits is solved, and the effective reduction of EMI radiation and improvement of equipment performance is achieved.
Patent Information
- Application Number
- CN202421834916.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-31
- Publication Date
- 2025-05-16
- Estimated Expiration
- 2034-07-31
AI Technical Summary
In digital circuits, the clock signal of the quartz crystal oscillator is prone to cause EMI radiation to exceed the standard.
By designing the inverted edge ratio of the crystal chip and the electrode size, and using a triangular wave of about 30KHz to modulate and spread spectrum with the product local oscillator clock, dispersing the clock frequency, expanding the spectrum, and reducing the power concentration of the signal spectrum.
Effectively reduce the EMI radiation generated by the clock signal, reduce the power by about 8~20dB, and improve the performance of the equipment and the stability of data transmission.
Smart Images
Figure CN222884651U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of quartz crystal oscillation, in particular to a quartz crystal oscillator with spread spectrum output. Background Art
[0002] A quartz crystal oscillator is an electronic component that can provide a stable clock. It is often used as a clock reference source in circuits to provide a stable clock reference for the circuit to run in an orderly manner. The reason why a quartz crystal oscillator can generate a stable clock frequency is that it uses a quartz wafer as an oscillation source. Quartz wafers, which are made of silicon dioxide, have a very stable natural frequency and a piezoelectric effect. They are a core material widely used in clock frequency devices.
[0003] However, in digital circuits, clock signals often require square wave signals. Therefore, to meet market demand, the clock output of most quartz crystal oscillators is square wave. Square wave is a pulse signal with a duty cycle of 50%, containing multiple harmonic components, and the power is concentrated on the center frequency. In EMC electromagnetic compatibility testing, it is often easy to cause EMI radiation to exceed the standard. Therefore, a quartz crystal oscillator with spread spectrum output is urgently needed to reduce the EMI radiation of its output clock signal. Utility Model Content
[0004] The utility model discloses a quartz crystal oscillator with spread spectrum output, aiming to solve the technical problem of excessive EMI radiation of clock signals in digital circuits.
[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:
[0006] A quartz crystal oscillator with spread spectrum output, comprising a quartz crystal oscillator body, and further comprising:
[0007] The quartz crystal oscillator body is composed of a ceramic base, a crystal piece, an IC integrated circuit and a binding gold wire. The IC integrated circuit is fixedly mounted on the ceramic base. The two ends of the binding gold wire are respectively connected to the ceramic base and the IC integrated circuit. The crystal piece is located above the IC integrated circuit, and the crystal piece is conductively bonded to the ceramic base.
[0008] In this solution, by designing the chamfer edge ratio and electrode size of the crystal piece, and by using a triangle wave of about 30KHz to modulate and spread the product local oscillator clock, and then buffering the output after modulation, the clock frequency generated by the local oscillator source is dispersed to the vicinity of the original center frequency, so that the spectrum can be expanded. Through the spread-spectrum clock signal, the power of the signal spectrum is no longer concentrated on the center frequency, but is dispersed to the vicinity of the center frequency. Through the spread-spectrum clock, the power can be reduced by about 8~20dB, thereby effectively reducing the EMI radiation generated by the clock signal.
[0009] In a preferred solution, an electrode is provided on the top of the quartz crystal sheet, and the electrode and the quartz crystal sheet form a crystal resonator.
[0010] The working principle of the crystal resonator is based on the piezoelectric effect. When an alternating electric field is applied, the crystal piece will undergo mechanical deformation, and the mechanical deformation will generate an alternating electric field. When the frequency of this mechanical vibration is equal to or close to the resonant frequency in the circuit, resonance will occur, generating a stable oscillation frequency.
[0011] In a preferred solution, the interior of the ceramic base is divided into an upper cavity and a lower cavity.
[0012] When in use, the interior of the ceramic base is divided into two cavities, the upper cavity is used to place the crystal piece, and the lower cavity is used to place the IC integrated circuit. Such a structure has a short internal line, which can reduce the signal reflection caused by impedance discontinuity during clock signal transmission, thereby improving signal quality and stability.
[0013] As can be seen from the above, a quartz crystal oscillator with spread spectrum output includes a quartz crystal oscillator body and also includes:
[0014] The quartz crystal oscillator body is composed of a ceramic base, a crystal piece, an IC integrated circuit and a binding gold wire. The IC integrated circuit is fixedly mounted on the ceramic base. The two ends of the binding gold wire are respectively connected to the ceramic base and the IC integrated circuit. The crystal piece is located above the IC integrated circuit, and the crystal piece is conductively bonded to the ceramic base. The quartz crystal oscillator with spread spectrum output provided by the utility model has the technical effect of effectively reducing the EMI radiation generated by the clock signal, improving the performance of the equipment and the stability of data transmission. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 This is an internal top view of a quartz crystal oscillator with spread spectrum output proposed by the utility model.
[0016] Figure 2 The utility model discloses an internal cross-sectional side view of a quartz crystal oscillator with spread spectrum output.
[0017] Figure 3 The utility model provides a schematic diagram of the gold-plated pad installation structure of a quartz crystal oscillator with spread spectrum output.
[0018] Figure 4 The utility model discloses a quartz crystal oscillator main circuit principle diagram of a quartz crystal oscillator with spread spectrum output.
[0019] Figure 5 This is a triangle wave modulation signal diagram of a quartz crystal oscillator with spread spectrum output proposed by the utility model.
[0020] Figure 6 This is a spectrum amplitude diagram of the clock before spectrum spreading of a quartz crystal oscillator with spectrum spreading output proposed by the utility model.
[0021] Figure 7 This is a spectrum amplitude diagram of a spread spectrum clock of a quartz crystal oscillator with spread spectrum output proposed by the utility model.
[0022] In the attached figure: 1. Electrode; 2. Crystal piece; 3. Conductive glue; 4. Top cover; 5. Quartz crystal oscillator body; 6. Binding gold wire; 7. IC integrated circuit; 8. Gold-plated pad; 9. Ceramic base. DETAILED DESCRIPTION
[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application usually described and marked in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.
[0024] The quartz crystal oscillator with spread spectrum output disclosed in the utility model is mainly used in digital circuits. The clock signal often requires a square wave signal. Therefore, in order to meet market demand, the clock output of most quartz crystal oscillators is a square wave. A square wave is a pulse signal with a duty cycle of 50%, containing multiple harmonic components, and the power is mainly concentrated on the center frequency. In EMC electromagnetic compatibility testing, it is often easy to cause EMI radiation to exceed the standard.
[0025] Reference Figure 1 , Figure 2 and Figure 3, a quartz crystal oscillator with spread spectrum output, the quartz crystal oscillator body 5 also includes:
[0026] The quartz crystal oscillator body 5 is composed of a ceramic base 9, a crystal piece 2, an IC integrated circuit 7 and a binding gold wire 6. The IC integrated circuit 7 is fixedly mounted on the ceramic base 9. The two ends of the binding gold wire 6 are respectively connected to the ceramic base 9 and the IC integrated circuit 7. The crystal piece 2 is located above the IC integrated circuit 7, and the crystal piece 2 is conductively bonded to the ceramic base 9.
[0027] It should be noted that the crystal piece 2 uses a high-Q quartz crystal piece as an oscillation source material (silver electrodes or gold electrodes are plated on the front and back of the crystal piece 2, and the size and shape of the electrode 1, the size of the crystal piece 2, the edge ratio and whether it is chamfered all affect its working Q value). There are multiple layers of ceramic circuit boards inside the ceramic base 9, which provide circuit conditions for the IC integrated circuit 7 and the crystal piece 2 to be turned on. The binding gold wire 6 is mainly used to connect the functional pads of the bare chip of the IC integrated circuit 7 with the circuit of the ceramic base 9.
[0028] Among them, the interior of the ceramic base 9 is divided into an upper cavity and a lower cavity. The upper cavity is used to place the crystal piece 2, and the lower cavity is used to place the IC integrated circuit 7. Such a structure has a short internal line, which can reduce the signal reflection caused by impedance discontinuity during clock signal transmission, thereby improving signal quality and stability.
[0029] Specifically, by designing the chamfer edge ratio of the crystal piece 2 and the size of the electrode 1, and by using a triangle wave of about 30KHz to modulate and spread the product's local oscillator clock, and then buffering the output after modulation, the clock frequency generated by the local oscillator source is dispersed to the vicinity of the original center frequency, so that the spectrum can be expanded. Through the spread-spectrum clock signal, the power of the signal spectrum is no longer concentrated on the center frequency, but is dispersed to the vicinity of the center frequency. Through the spread-spectrum clock, the power can be reduced by about 8~20dB, thereby effectively reducing the EMI radiation generated by the clock signal.
[0030] Reference Figure 1 and Figure 2 In a preferred embodiment, an electrode 1 is provided on the top of the crystal piece 2, and the electrode 1 and the crystal piece 2 constitute a crystal resonator. The working principle of the crystal resonator is based on the piezoelectric effect. When an external alternating electric field acts on the crystal piece 2, the crystal piece 2 will undergo mechanical deformation, and the mechanical deformation will generate an electric field. When the frequency in the circuit is close to or equal to the natural frequency of the crystal piece 2, resonance will occur, generating a stable oscillation frequency.
[0031] Reference Figure 1 and Figure 2In a preferred embodiment, conductive glue 3 is provided on the top outer wall of the crystal piece 2 near the two corners, one end of the electrode 1 is connected to the conductive glue 3, the electrode 1 is connected to the ceramic base 9, and the bottom of the ceramic base 9 is provided with gold-plated pads 8 near the four corners. The conductive glue 3 is used to fix the electrical signal of the electrode 1 to the input pin of the IC integrated circuit 7. The IC integrated circuit 7 is connected to the gold-plated pad 8 by binding the gold wire 6. The gold-plated pad 8 is used to improve the contact and is externally connected to the circuit board. The conductive glue 3 mainly plays a role of fixing the conduction, and conducts the electrical signal of the electrode 1 to the gold-plated pad 8, which is convenient for users to use.
[0032] Reference Figure 2 In a preferred embodiment, a top cover 4 is provided on the top outer wall of the quartz crystal oscillator body 5 , and the top cover 4 is located directly above the crystal plate 2 .
[0033] Reference Figure 4 In a preferred embodiment, U1, Rd, Rf, Cg, Cd, and Y1 in the attached drawings constitute a three-point oscillation circuit, which is the oscillation source of the product, wherein Y1 refers to a crystal piece with electrodes attached, which constitutes a crystal resonator, U1 is a reverse amplifier, which provides amplitude and phase conditions for the oscillation circuit, Rf is a feedback resistor, which makes the reverse amplifier work in the linear amplification area, Rd is an output current limiting resistor, which reduces the excitation power of the crystal resonance, and Gg and Cd are the load capacitors of the oscillation circuit, which are also two necessary capacitors to constitute a three-point oscillation circuit. The frequency output by the inverter U1 can enter the U2 spread spectrum modulation unit, and finally the spread spectrum clock is output through the U3 buffer, reducing the impact of the later stage on the product. U4 is a voltage regulator, which provides a stabilized supply voltage for the inverter U1 of the local oscillator to improve the stability of the oscillator.
[0034] Reference Figure 5 In a preferred embodiment, fm is a triangular wave modulation signal, and fc is a normal clock signal. This schematic diagram is a modulation method, which is center spread spectrum modulation. There are also down spread spectrum modulation and up spread spectrum modulation methods. In the field of oscillator clocks, center spread spectrum modulation and down spread spectrum modulation are used. The modulation principle is as follows Figure 5 As shown, the normal clock signal fc is periodically changed in frequency along with the modulation signal fm, so that the average frequency of the clock signal fc remains unchanged in one cycle of the modulation signal fm. The modulation signal fm adopts a low-frequency triangle wave of about 30KHz. The modulation signal fm is used to determine the clock frequency expansion period rate. The clock frequency changes by Δf within this period and returns to the initial frequency. Usually, the spectrum modulation rate is reduced to achieve frequency smoothing modulation, reduce the jitter parameters of the modulated clock period, and output the spread spectrum clock through the U3 buffer to reduce the impact of the subsequent stage on the product.
[0035] Reference Figure 6 and Figure 7 In a preferred embodiment, Figure 6 is the spectrum amplitude of the clock before spread spectrum, Figure 7 The two black lines represent the power difference before and after the spread spectrum. Before the spread spectrum, the spectrum amplitude of the clock is a sharp pulse, and the power is higher than that of the spread spectrum clock. After the spread spectrum, the sharp pulse is flattened and the peak power is significantly reduced. The power of the spread spectrum clock can be reduced by about 8~20dB, which greatly reduces the EMI radiation of the clock.
[0036] Working principle: When in use, by designing the chamfer edge ratio of the crystal piece 2 and the size of the electrode 1, and through the normal clock signal fc, the frequency of the modulation signal fm is changed periodically, so that the clock signal fc is in one cycle of the modulation signal fm, so that the average frequency of fc remains unchanged. The modulation signal fm adopts a low-frequency triangle wave of about 30KHz. The modulation signal fm is used to determine the clock frequency expansion period rate. The clock frequency changes Δf within this period and returns to the initial frequency. Usually, the spectrum modulation rate is reduced to achieve frequency smoothing modulation and reduce the jitter parameters of the modulated clock cycle. Then, the modulation signal adopts a triangle wave and a spread-spectrum clock to be output through the U3 buffer, and the clock frequency generated by the local oscillator source is dispersed to the vicinity of the original center frequency, so that the spectrum can be expanded. Through the spread-spectrum clock signal, the power of the signal spectrum is no longer concentrated on the center frequency, but is dispersed to the vicinity of the center frequency. Through the spread-spectrum clock, the power can be reduced by about 8~20dB, thereby effectively reducing the EMI radiation generated by the clock signal.
[0037] The above is only a preferred specific implementation of the utility model, but the protection scope of the utility model is not limited to this. The replacement can be a replacement of part of the structure, device, method step, or a complete technical solution. Equivalent replacement or change based on the technical solution of the utility model and its utility model concept should be included in the protection scope of the utility model.
Claims
1. A quartz crystal oscillator with spread spectrum output, comprising a quartz crystal oscillator body (5), characterized in that: Also includes: The quartz crystal oscillator body (5) is composed of a ceramic base (9), a crystal piece (2), an IC integrated circuit (7) and a binding gold wire (6); the IC integrated circuit (7) is fixedly mounted on the ceramic base (9); two ends of the binding gold wire (6) are respectively connected to the ceramic base (9) and the IC integrated circuit (7); the crystal piece (2) is located above the IC integrated circuit (7); and the crystal piece (2) and the ceramic base (9) are conductively bonded.
2. A quartz crystal oscillator with spread spectrum output according to claim 1, characterized in that: An electrode (1) is provided on the top of the crystal piece (2), and the electrode (1) and the crystal piece (2) form a crystal resonator.
3. A quartz crystal oscillator with spread spectrum output according to claim 2, characterized in that: Conductive glue (3) is provided on the top outer wall of the crystal sheet (2) near two corners, and one end of the electrode (1) is connected to the conductive glue (3).
4. A quartz crystal oscillator with spread spectrum output according to claim 3, characterized in that: The electrode (1) is connected to the ceramic base (9), and gold-plated pads (8) are provided at the bottom of the ceramic base (9) near the four corners.
5. A quartz crystal oscillator with spread spectrum output according to claim 4, characterized in that: The conductive glue (3) is used to fix the electrical signal of the electrode (1) to the input pin of the IC integrated circuit (7); the IC integrated circuit (7) is connected to the gold-plated pad (8) via the binding gold wire (6); the gold-plated pad (8) is used to improve contact and is externally connected to a circuit board.
6. A quartz crystal oscillator with spread spectrum output according to claim 1, characterized in that: A top cover (4) is provided on the top outer wall of the quartz crystal oscillator body (5), and the top cover (4) is located directly above the crystal plate (2).
7. A quartz crystal oscillator with spread spectrum output according to claim 6, characterized in that: The interior of the ceramic base (9) is divided into an upper cavity and a lower cavity.