Quartz crystal oscillator-based LC oscillation circuit and system chip

Abstract

The invention relates to an LC oscillation circuit based on a quartz crystal oscillator and a system chip, a quartz crystal in the quartz crystal oscillation circuit is replaced by an inductor and is used as the LC oscillation circuit, and a test verifies that the novel LC oscillation circuit can provide stable clock output, so that the novel LC oscillation circuit can support the stable clock output according to different performance and cost requirements. The clock effect of the quartz crystal oscillation circuit and the clock effect of the LC oscillation circuit are achieved in a compatible mode under the condition that the cost and pins of a system chip are not increased, and more application flexibility is provided for the system chip.

Description

Technical Field

[0001] The invention belongs to the technical field of clock generation circuits and relates to an LC oscillation circuit and a system chip based on a quartz crystal oscillator. Background Art

[0002] In various electronic systems, a relatively accurate low-temperature drift oscillator circuit is often required to generate a clock source. Commonly used technologies include quartz crystal oscillator circuits and three-point LC oscillator circuits. Quartz crystal oscillator circuits usually have better performance, but are more expensive, while LC oscillator circuits have slightly worse frequency accuracy, but are cheaper. Traditional three-point LC oscillator circuits are not compatible with quartz crystals. If the same system chip needs to meet application requirements with different frequency accuracies at the same time, two different oscillator circuits are often required, which means that more chip pins and chip area are required. Therefore, how to implement different oscillator circuits on the same system chip has become a technical problem to be solved. Summary of the invention

[0003] In view of the above problems, the present invention proposes an LC oscillation circuit based on a quartz crystal oscillator and a system chip, which can be compatible with implementing different oscillation circuits on the same system chip.

[0004] In order to achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: On the one hand, a quartz crystal oscillator-based LC oscillation circuit is provided, including an amplifier Amp1, an inductor L0, a capacitor C101 and a capacitor C102, one end of the capacitor C101 and the capacitor C102 are respectively grounded, the other end of the capacitor C101 is respectively connected to the input end of the amplifier Amp1 and one end of the inductor L10, and the other end of the capacitor C102 is respectively connected to the output end of the amplifier Amp1 and the other end of the inductor L10.

[0005] On the other hand, a system chip is also provided, in which a quartz crystal-based LC oscillator circuit for providing a clock source is provided. The quartz crystal-based LC oscillator circuit includes an amplifier Amp1, an inductor L10, a capacitor C101 and a capacitor C102. One end of the capacitor C101 and the capacitor C102 are respectively grounded, the other end of the capacitor C101 is respectively connected to the input end of the amplifier Amp1 and one end of the inductor L10, and the other end of the capacitor C102 is respectively connected to the output end of the amplifier Amp1 and the other end of the inductor L10.

[0006] In one embodiment, the system chip is an LED driver chip or a GPU chip.

[0007] The above technical solution has the following advantages and beneficial effects: The above-mentioned LC oscillation circuit and system chip based on quartz crystal oscillator, by replacing the quartz crystal in the quartz crystal oscillation circuit with an inductor and using it as an LC oscillation circuit, have been verified through experiments that the new LC oscillation circuit can give a stable clock output, thereby supporting different performance and cost requirements without increasing the cost and pins of the system chip, and being compatible with the clock effects of the quartz crystal oscillation circuit and the LC oscillation circuit, thereby providing more application flexibility for the system chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0009] Figure 1 It is a schematic diagram of the structure of a traditional three-point LC oscillation circuit; Figure 2 It is a schematic diagram of the structure of a commonly used quartz crystal oscillator circuit; Figure 3 is the quartz crystal equivalent circuit; Figure 4 is a schematic structural diagram of an LC oscillation circuit based on a quartz crystal oscillator in an embodiment; Figure 5 A graph showing an impedance frequency sweep of an oscillator circuit in one embodiment; Figure 6 is a schematic structural diagram of an LC oscillation circuit based on a quartz crystal oscillator in another embodiment; Figure 7 1 is a simulation waveform compatible with the quartz crystal Xtal and the LC oscillation circuit design in an embodiment, (a) is the simulation waveform corresponding to the quartz crystal Xtal, and (b) is the simulation waveform corresponding to the LC oscillation. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and Examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0011] It should be noted that the reference to "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The presentation of this phrase at various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It will be appreciated by those skilled in the art that the embodiments described herein may be combined with other embodiments. The term "and / or" used in the specification of the present invention and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0012] The following will describe the implementation of the present invention in detail with reference to the accompanying drawings in the embodiment diagram of the present invention.

[0013] Commonly used capacitor three-point LC oscillator circuits such as Figure 1 As shown, it includes resistor R0, resistor R1, resistor R2, inductor L0, capacitor C0, capacitor C1 and transistor NM0, where VDD is the power supply and VSS is the ground. The commonly used quartz crystal oscillator circuit is as follows Figure 2 As shown, it includes an amplifier Amp, a quartz crystal Xtal, a capacitor C11 and a capacitor C12. The equivalent circuit of the quartz crystal can be as follows: Figure 3 As shown, it includes an inductor L, a capacitor C, a resistor R and a capacitor Cm. The circuit form of the commonly used quartz crystal oscillator circuit is different from the circuit form of the capacitor three-point LC oscillator circuit. Since the LC oscillator circuit itself is also a frequency selection network like the quartz crystal oscillator circuit, the present invention directly uses the quartz oscillator circuit for the LC oscillator circuit, wherein a relatively low-cost inductor is used to replace the high-cost quartz crystal, thereby providing more system flexibility without increasing the system chip area and pins.

[0014] In one embodiment, Figure 4 As shown, a quartz crystal oscillator-based LC oscillation circuit 100 is provided, including an amplifier Amp1, an inductor L10, a capacitor C101 and a capacitor C102, one end of the capacitor C101 and the capacitor C102 are respectively grounded, the other end of the capacitor C101 is respectively connected to the input end of the amplifier Amp1 and one end of the inductor L0, and the other end of the capacitor C102 is respectively connected to the output end of the amplifier Amp1 and the other end of the inductor L0.

[0015] It is understandable that in actual use, the same PCB design is often required for products of different levels, and products of different levels and costs can be achieved by replacing components. At the same time, the number of chip pins and the packaging cost are positively correlated with the chip area. Making two different oscillators at the same time usually leads to higher chip costs. Therefore, under the constraints of the number of chip pins and chip cost, an oscillator circuit compatible with quartz crystal and LC oscillation is proposed.

[0016] The oscillator circuit compatible with quartz crystal and LC oscillation is essentially a negative resistance oscillator, and its amplifier needs to provide energy to offset the positive resistance loss of the LC oscillation circuit or quartz crystal. At the target frequency of the oscillator circuit, the oscillator circuit should provide a sufficiently high negative resistance to compensate for the positive resistance loss of the LC oscillation circuit or quartz crystal, such as Figure 5 As shown, it is a curve of impedance frequency scanning of the oscillator circuit, where the unit of the scanning impedance is kiloohm. It can be seen that within the operating frequency range of the oscillator circuit, the oscillator circuit exhibits a negative resistance characteristic.

[0017] The circuit connection structure of the above amplifier Amp1, inductor L10, capacitor C101 and capacitor C102 is the same as the circuit connection structure of the commonly used quartz crystal oscillator circuit, except that the quartz crystal is replaced by inductor L10, and inductor L10 can use a low DCR (referring to the resistance of the inductor to the DC current in the absence of an AC signal) inductor. The specific inductor model can be selected according to the cost and accuracy requirements of different system chips, and can be matched with the corresponding capacitor model. The improved new LC oscillator circuit 100 based on quartz crystal oscillator is used as the LC oscillator circuit in the system chip. It has been verified through experiments that it can provide a stable clock output, and its clock frequency is obtained by the following formula:

[0018] in, L is the inductance value of inductor L10, C is the capacitance value of capacitor C101 and capacitor C102. The LC oscillator circuit 100 based on the quartz crystal oscillator can also be compatible with the basic functions of the quartz crystal oscillator circuit, thereby providing more system flexibility without increasing the system chip cost and pin number.

[0019] The above-mentioned LC oscillation circuit 100 based on quartz crystal oscillator, by replacing the quartz crystal in the quartz crystal oscillation circuit with an inductor and using it as an LC oscillation circuit, has been verified through experiments that the new LC oscillation circuit can provide a stable clock output, thereby being able to support different performance and cost requirements without increasing the cost and pins of the system chip, and being compatible with the clock effects of the quartz crystal oscillation circuit and the LC oscillation circuit, thereby providing more application flexibility for the system chip.

[0020] In one embodiment, Figure 6 As shown, the LC oscillator circuit 100 based on the quartz crystal oscillator may further include a quartz crystal Xtal and a bypass resistor Rp. The quartz crystal Xtal is connected in parallel with the inductor L10, and the bypass resistor Rp is connected in parallel with the quartz crystal Xtal. When the inductor L10 is open, the quartz crystal Xtal closes the circuit.

[0021] It can be understood that due to the quality factor of quartz crystal, its price is usually higher than that of LC oscillation circuit. The inductor with lower price on the market usually has larger resistance. In order to compensate for the DC loss of the inductor, the compatible oscillator circuit in this embodiment usually requires a larger amplifier gain and bias current. When the quartz crystal Xtal is actually used, the signal swing may be too large, and the excessive signal swing may cause clock signal distortion and reduce the service life of the chip. In order to overcome this problem, a bypass resistor Rp can be added to the quartz crystal Xtal. The bypass resistor Rp can be selected and connected in time according to the needs to increase the branch current loss of the quartz crystal Xtal and control the signal swing of the quartz crystal Xtal. Figure 6 As shown, the paths where the inductor L10 and the quartz crystal Xtal are located can be selectively turned on or off as needed through switch elements. Figure 7 The figure shows a simulation waveform that is compatible with the quartz crystal Xtal and LC oscillation circuit design. (a) is the simulation waveform corresponding to the quartz crystal Xtal, and (b) is the simulation waveform corresponding to the LC oscillation.

[0022] In one embodiment, a system chip is further provided, in which a quartz crystal oscillator-based LC oscillator circuit for providing a clock source is provided. The quartz crystal oscillator-based LC oscillator circuit includes an amplifier Amp1, an inductor L10, a capacitor C101 and a capacitor C102. One end of the capacitor C101 and the capacitor C102 are respectively grounded, the other end of the capacitor C101 is respectively connected to the input end of the amplifier Amp1 and one end of the inductor L10, and the other end of the capacitor C102 is respectively connected to the output end of the amplifier Amp1 and the other end of the inductor L10.

[0023] It can be understood that the above-mentioned system chip can be a system chip that requires a clock source in various electronic systems. It provides the required clock source by carrying a new LC oscillation circuit based on a quartz crystal oscillator, thereby providing a stable clock output for the system chip, and supporting the clock effects of the quartz crystal oscillation circuit and the LC oscillation circuit according to different performance and cost requirements without increasing the cost and pins of the system chip, thereby providing more application flexibility for the system chip.

[0024] In one embodiment, the LC oscillator circuit based on the quartz crystal of the system chip may further include a quartz crystal Xtal and a bypass resistor Rp. The quartz crystal Xtal is connected in parallel with the inductor L10, and the bypass resistor Rp is connected in parallel with the quartz crystal Xtal. When the inductor L10 is open, the quartz crystal Xtal closes the circuit. A more flexible design compatible with the quartz crystal Xtal and the LC oscillator circuit is achieved.

[0025] In one embodiment, the system chip is an LED driver chip or a GPU chip.

[0026] It can be understood that the system chip in this embodiment can be an LED driver chip in the field, or it can be other various types of GPU chips used for image processing. By installing a new quartz crystal-based LC oscillation circuit in these chips to provide the required clock source, the cost of the chip can be effectively reduced while obtaining the required clock output.

[0027] For the specific definition of the above-mentioned novel LC oscillator circuit based on quartz crystal oscillator, please refer to the definition of the LC oscillator circuit 100 based on quartz crystal oscillator in the above text, which will not be repeated here.

[0028] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0029] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection of the invention. It should be pointed out that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. An LC oscillator circuit based on a quartz crystal oscillator, characterized in that: It includes an amplifier Amp1, an inductor L10, a capacitor C101 and a capacitor C102, one end of the capacitor C101 and the capacitor C102 are respectively grounded, the other end of the capacitor C101 is respectively connected to the input end of the amplifier Amp1 and one end of the inductor L10, and the other end of the capacitor C102 is respectively connected to the output end of the amplifier Amp1 and the other end of the inductor L10.

2. The LC oscillator circuit based on a quartz crystal oscillator according to claim 1, characterized in that: It also includes a quartz crystal Xtal and a bypass resistor Rp. The quartz crystal Xtal is connected in parallel with the inductor L10. The bypass resistor Rp is connected in parallel with the quartz crystal Xtal. When the inductor L10 is open, the quartz crystal Xtal closes the circuit.

3. A system chip, characterized in that: The system chip is provided with an LC oscillation circuit based on a quartz crystal for providing a clock source. The LC oscillation circuit based on a quartz crystal includes an amplifier Amp1, an inductor L10, a capacitor C101 and a capacitor C102. One end of the capacitor C101 and the capacitor C102 are respectively grounded, the other end of the capacitor C101 is respectively connected to the input end of the amplifier Amp1 and one end of the inductor L10, and the other end of the capacitor C102 is respectively connected to the output end of the amplifier Amp1 and the other end of the inductor L10.

4. The system chip according to claim 3, characterized in that: The LC oscillation circuit based on the quartz crystal oscillator further includes a quartz crystal Xtal and a bypass resistor Rp. The quartz crystal Xtal is connected in parallel with the inductor L10. The bypass resistor Rp is connected in parallel with the quartz crystal Xtal. When the inductor L10 is open, the quartz crystal Xtal closes the circuit.

5. The system chip according to claim 3 or 4, characterized in that: The system chip is an LED driver chip or a GPU chip.

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