An ultra-wideband crystal drive circuit
By integrating low-frequency and mid-to-high-frequency oscillator circuits into the same chip and adjusting the resistance value through a feedback resistor module, the problem that existing crystal driver circuits cannot simultaneously support low-frequency and mid-to-high-frequency frequencies has been solved, achieving a crystal driver circuit design with smaller area and lower cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHENGDU ANALOG CIRCUIT TECH INC
- Filing Date
- 2021-09-09
- Publication Date
- 2026-07-14
AI Technical Summary
Existing crystal driver circuits cannot simultaneously support low-frequency and medium-to-high-frequency crystal oscillators on the same chip, resulting in increased chip area, reduced available package pins, and increased cost.
Design an ultra-wideband crystal driver circuit that integrates low-frequency and mid-to-high-frequency oscillator circuits into the same chip, and adjusts the resistance value through a feedback resistor module to start the low-frequency or mid-to-high-frequency crystals respectively using a selection signal, thereby reducing the number of pins and external resistors.
This enables a single chip to support both low-frequency and mid-to-high-frequency crystal oscillators, reducing circuit design area and chip cost, while increasing chip flexibility and the number of available package pins.
Smart Images
Figure CN113872591B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of integrated circuit technology, and in particular to a crystal driving circuit, especially an ultra-wideband crystal driving circuit. Background Technology
[0002] Since its invention in the 1920s, crystal drivers have seen rapid development in both theoretical research and manufacturing, resulting in significant improvements in various performance indicators. As a clock frequency source, crystal oscillators, compared to other types of oscillators, are widely used in military and consumer electronics fields due to their superior Q value, frequency accuracy, and stability. In the field of integrated circuits, the role of I / O interface integrated circuits is crucial for ensuring the effective and rational transmission of crystal frequency signals to the chip core.
[0003] As the performance requirements for crystal driver circuits become increasingly demanding, designers are exploring various directions, from 32.768kHz (low-frequency) crystal driver circuits to those operating at several MHz or even tens of MHz (mid-to-high-frequency) levels. However, in existing crystal driver circuits, both low-frequency (32.768kHz) and mid-to-high-frequency crystal driver circuits are located independently on different chips. If a single chip needs to support both low-frequency and mid-to-high-frequency crystal oscillators, even if the two frequencies do not coexist in the chip system, separate crystal driver circuits, package pins, and external resistors must be provided within the chip for each oscillator. This results in an increase in chip area, a reduction in available package pins, and a significant increase in cost. Summary of the Invention
[0004] The main objective of this invention is to provide an ultra-wideband crystal driving circuit that can simultaneously support low-frequency crystal oscillators and medium-to-high-frequency crystal oscillators on a single chip.
[0005] To achieve the above objectives, the present invention provides an ultra-wideband crystal driving circuit for driving low-frequency or mid-to-high-frequency crystals and outputting low-frequency or mid-to-high-frequency crystal oscillation signals. The crystal driving circuit includes a feedback resistor module, an oscillation circuit module, and a first selector. The feedback resistor module is connected to the oscillation circuit module, which is connected to the first selector, an external crystal, and an external load. The first selector is connected to the oscillation circuit module. The oscillation circuit module further includes a low-frequency oscillator circuit and a mid-to-high-frequency oscillator circuit, respectively used to start the low-frequency and mid-to-high-frequency crystals. When an external crystal needs to be started, the driving circuit connects the corresponding crystal according to the required frequency. A control signal is sent to the feedback resistor module to configure its resistance value to the value required to start the crystal. A selection signal is sent to the oscillation circuit module to turn on one of the oscillator circuits while turning off the other. The first selector outputs the selected crystal oscillation signal to subsequent circuits according to the selection signal.
[0006] Preferably, the driving circuit further includes an output module connected to the first selector, which is used to increase the driving capability of the crystal oscillation signal and output it.
[0007] Preferably, the driving circuit further includes a trigger module, which is connected to the output module and the external load terminal, and is used to send the externally input clock signal to the output module.
[0008] Preferably, the trigger module is a Schmitt trigger.
[0009] Preferably, the crystal driving circuit further includes a second selector, which is connected to the trigger module and the first selector, and is used to output the signal of the trigger module or the first selector.
[0010] Preferably, the driving circuit further includes a register module, which configures the control signal to adjust the resistance value of the feedback resistor module and configures the selection signal to select whether to turn on the low-frequency oscillator circuit or the medium-high frequency oscillator circuit; the register module is also configured with a first start signal or a second start signal to start the low-frequency oscillator circuit or the medium-high frequency oscillator circuit respectively.
[0011] Preferably, the register module also sends a bypass control signal to the trigger module, the oscillation circuit module, and the second selector to connect the external load terminals of the trigger module and the crystal drive circuit, turn off the oscillation circuit module, and enable the second selector to select the output of an external clock signal.
[0012] Preferably, the feedback resistor module includes multiple resistors connected in series, and each of the multiple resistors connected in series is connected in parallel with a switch. The control signal adjusts the resistance value of the feedback resistor module by turning the control switch on or off.
[0013] Preferably, the resistance value of the feedback resistor module is in the range of 500 Kohm to 10 Mohm.
[0014] The technical solution of this invention integrates the low-frequency oscillator circuit and the mid-to-high-frequency oscillator circuit into the same chip. At the same time, by adjusting the resistance value of the feedback resistor module, the feedback resistance required by the oscillator circuit module is met. Then, by selecting the signal to connect the low-frequency or mid-to-high-frequency oscillator circuit respectively, the low-frequency or mid-to-high-frequency crystal is started respectively, which meets the requirements of the chip system for different clocks. This reduces the circuit design area, reduces the use of pins and external resistors, and greatly reduces the chip area and chip cost. Attached Figure Description
[0015] Figure 1 This is a circuit schematic diagram of the ultra-wideband crystal driving circuit of the present invention;
[0016] Figure 2 This is a circuit diagram of the ultra-wideband crystal driving circuit of the present invention;
[0017] Figure 3 This is a circuit diagram of the feedback resistor module in the ultra-wideband crystal driving circuit of the present invention.
[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0019] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0020] The invention will be further described below with reference to the accompanying drawings.
[0021] This invention provides an ultra-wideband crystal driving circuit that supports low-frequency and medium-to-high-frequency crystal driving, and is used to provide clock signals of different frequencies for chip systems.
[0022] like Figure 1 , Figure 2As shown, this ultra-wideband crystal driving circuit is used to drive low-frequency or mid-to-high-frequency crystals and output low-frequency or mid-to-high-frequency crystal oscillation signals. It includes a feedback resistor module, an oscillation circuit module, and a first selector MUX1. The feedback resistor module is connected to the oscillation circuit module, which is connected to the first selector MUX1, an external crystal, and external load terminals X0 and X1. The first selector MUX1 is connected to the oscillation circuit module. The oscillation circuit module also includes a low-frequency oscillator circuit and a mid-to-high-frequency oscillator circuit, used to start the low-frequency and mid-to-high-frequency crystals, respectively. When an external crystal needs to be started, the driving circuit connects the corresponding crystal according to the required clock frequency. A control signal RF_SEL is sent to the feedback resistor module to configure its resistance value to the value required to start the crystal. A selection signal REG_SEL is sent to the oscillation circuit module to turn on one of the oscillator circuits while turning off the other. The first selector MUX1 outputs the selected crystal oscillation signal to subsequent circuits according to the selection signal REG_SEL.
[0023] Because this embodiment of the invention integrates the low-frequency oscillator circuit and the mid-to-high-frequency oscillator circuit into the same chip, and by adjusting the resistance value of the feedback resistor module to meet the feedback resistance required by the oscillator circuit module, and then by using the selection signal REG_SEL to connect the low-frequency or mid-to-high-frequency oscillator circuit respectively, the low-frequency or mid-to-high-frequency crystal is started respectively, thus meeting the chip system's requirements for different clocks. This reduces the circuit design area, the number of pins used and the number of external resistors, and greatly reduces the chip area and chip cost.
[0024] Specifically, the specific circuit structures of the low-frequency oscillator circuit and the medium-to-high-frequency oscillator circuit in the oscillation circuit module can use any oscillation circuit disclosed in the prior art, as long as they respectively meet the requirements for starting the low-frequency crystal or the medium-to-high-frequency crystal.
[0025] In a specific embodiment, when the chip system requires a low-frequency clock signal, the crystal driver circuit connects a low-frequency crystal to its external load terminals X0 and X1 and connects a load to ground. A control signal RF_SEL is sent to the feedback resistor module to configure its resistance value to the value required to start the low-frequency crystal. A selection signal REG_SEL is sent to the low-frequency oscillator circuit to turn on the low-frequency oscillator circuit and simultaneously turn off the mid-to-high frequency oscillator circuit. After the low-frequency crystal starts, the first selector MUX1 selects, according to the selection signal REG_SEL, to output the low-frequency crystal oscillation signal to subsequent circuits.
[0026] In another specific embodiment, when the chip system requires a mid-to-high frequency clock signal, the crystal driver circuit connects a mid-to-high frequency crystal to its external load terminals X0 and X1, and connects a load to ground. A control signal RF_SEL is sent to the feedback resistor module to configure its resistance value to the value required to start the mid-to-high frequency crystal. A selection signal REG_SEL is sent to the mid-to-high frequency oscillator circuit to turn on the mid-to-high frequency oscillator circuit and simultaneously turn off the low-frequency oscillator circuit. After the mid-to-high frequency crystal starts, the first selector MUX1 selects, according to the selection signal REG_SEL, to output the mid-to-high frequency crystal oscillation signal to subsequent circuits.
[0027] In a preferred embodiment, such as Figure 2 As shown, the crystal driving circuit also includes a register module. This register module configures the control signal RF_SEL to adjust the resistance value of the feedback resistor module and configures the selection signal REG_SEL to select whether to activate the low-frequency oscillator circuit or the mid-to-high-frequency oscillator circuit. The register module also configures a first start signal 32K_IOPSEL or a second start signal MF_IOPSEL to activate the low-frequency oscillator circuit or the mid-to-high-frequency oscillator circuit, respectively. Specifically, the first start signal 32K_IOPSEL is used to activate the low-frequency oscillator circuit, and the second start signal MF_IOPSEL is used to activate the mid-to-high-frequency oscillator circuit.
[0028] In a specific embodiment, when the chip system requires a low-frequency clock signal, the crystal driver circuit connects a low-frequency crystal to its external load terminals X0 and X1 and connects a load to ground. The register module sends a control signal RF_SEL to the feedback resistor module to configure the resistance value of the feedback resistor module to the resistance value required to start the low-frequency crystal. The register module sends a selection signal REG_SEL to the low-frequency oscillator circuit to turn on the low-frequency oscillator circuit and simultaneously turn off the mid-to-high frequency oscillator circuit. The register module sends a first start signal 32K_IOPSEL to the low-frequency oscillator circuit to enable the low-frequency oscillator circuit to work normally and start the low-frequency crystal. The register module sends a selection signal REG_SEL to the first selector MUX1, which selects the low-frequency crystal oscillation signal to be output to subsequent circuits. Specifically, the first start signal 32K_IOPSEL is a suitable low-frequency crystal start-up current. This start-up current can be set according to the specific frequency of the crystal and the actual circuit technology.
[0029] In another specific embodiment, when the chip system requires a mid-to-high frequency clock signal, the crystal driver circuit connects a mid-to-high frequency crystal to its external load terminals X0 and X1 and connects a load to ground. The register module sends a control signal RF_SEL to the feedback resistor module to configure the resistance value of the feedback resistor module to the resistance value required to start the mid-to-high frequency crystal. The register module sends a selection signal REG_SEL to the mid-to-high frequency oscillator circuit to turn on the mid-to-high frequency oscillator circuit and turn off the low-frequency oscillator circuit. The register module sends a second start signal MF_IOPSEL to the mid-to-high frequency oscillator circuit to enable the mid-to-high frequency oscillator circuit to work normally and start the mid-to-high frequency crystal. The register module sends a selection signal REG_SEL to the first selector MUX1, and the first selector MUX1 selects the mid-to-high frequency crystal oscillation signal to be output to subsequent circuits. Specifically, the second start signal MF_IOPSEL is a suitable mid-to-high frequency crystal start-up current. This start-up current can be set according to the specific frequency of the crystal and the actual circuit technology conditions.
[0030] In a preferred embodiment, such as Figure 1 , Figure 2 As shown, the driving circuit further includes an output module VOUT, which is connected to the first selector MUX1 and is used to increase the driving capability of the crystal oscillation signal and output it. The output module VOUT is used to output the crystal oscillation signal of the driving circuit and increase the driving capability.
[0031] In a preferred embodiment, such as Figure 1 , Figure 2 As shown, the driving circuit also includes a trigger module (BUFFER), which is connected to the output module VOUT and the external load terminals X0 and X1. The BUFFER is used to send the externally input clock signal to the output module VOUT. The externally input clock signal is input through the external load terminals X0 and X1, replacing the crystal driving clock, and can be input according to actual needs, greatly increasing flexibility. Specifically, the trigger module (BUFFER) is a Schmitt trigger.
[0032] Furthermore, such as Figure 1 , Figure 2 As shown, the crystal driving circuit further includes a second selector MUX2, which is connected to the trigger module BUFFER and the first selector MUX1, and is used to output the signal of the trigger module BUFFER or the first selector MUX1.
[0033] Furthermore, the register module also sends a bypass control signal BYP to the trigger module BUFFER, the oscillation circuit module, and the second selector MUX2 to connect the external load terminals X0 and X1 of the trigger module BUFFER and the crystal driver circuit, turn off the oscillation circuit module, and enable the second selector MUX2 to select the output external clock signal.
[0034] When the chip system requires a clock signal other than the crystal driver clock, it can select an externally input clock signal. Specifically, the register module inputs a bypass control signal BYP to the oscillation circuit module, the trigger module BUFFER, and the second selector MUX2 to shut down the oscillation circuit module. The external clock signal is input from the external load terminals X0 and X1 to the trigger module BUFFER, and then sent by the trigger module BUFFER to the second selector MUX2. The second selector MUX2 selects the external clock signal for output. In a specific embodiment, the external clock signal can be input according to the specific clock requirements of the chip system.
[0035] In this embodiment of the invention, in actual use, an external crystal or an external clock signal can be selected according to the required frequency. The resistance value of the feedback resistor module is controlled by the register module, and the low-frequency oscillator circuit or the medium-to-high-frequency oscillator circuit is selected by the register module.
[0036] In a preferred embodiment, the feedback resistor module includes multiple resistors connected in series, and each of the multiple series resistors is connected in parallel with a switch. The control signal RF_SEL adjusts the resistance value of the feedback resistor module by controlling the switching on or off.
[0037] Furthermore, the resistance value of the feedback resistor module ranges from 500 Kohm to 10 Mohm. In a specific embodiment, the low-frequency crystal generally refers to a 32.768K crystal, and the corresponding feedback resistor value when this crystal is operating is generally 10 Mohm; the mid-to-high frequency crystal is generally a 4-32M crystal, and the corresponding feedback resistor value when this crystal is operating is generally 500 Kohm to 2 Mohm. In other embodiments, the required crystal can be connected according to user needs, and the resistance value range of the feedback resistor module can be set according to the crystal. The specific resistance value can be pre-adjusted according to the actual usage.
[0038] Specifically, such as Figure 3As shown, the feedback resistor module includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4 connected in series. The other ends of the first resistor R1 and the fourth resistor R4 are also connected to the oscillation circuit module. The second resistor R2 is connected in parallel with the first switch S1, the third resistor R3 is connected in parallel with the second switch S2, and the fourth resistor R4 is connected in parallel with the third switch S3. The register module sends control signals RF_SEL to the first switch S1, the second switch S2, and the third switch S3 respectively to control their on or off states. Specifically, the first control sub-signal RF_SEL... <1> Used to control the opening or closing of the first switch S1; the second control sub-signal RF_SEL <2> Used to control the opening or closing of the second switch S2; the third control sub-signal RF_SEL <3> This is used to control the on / off state of the third switch S3. The preset resistance values of the first resistor R1, second resistor R2, third resistor R3, and fourth resistor R4 are 500 Kohm, 1.5 Mohm, 3 Mohm, and 5 Mohm, respectively. When driving a low-frequency 32.768K crystal, turning on all resistors satisfies the required feedback resistance values for the low-frequency crystal's operation. When driving a mid-to-high frequency 4-32M crystal, turning on the corresponding resistor values satisfies the requirements for the mid-to-high frequency crystal's operation. In other embodiments, the number of resistors and switches can also be preset according to actual needs. Specific implementation examples:
[0040] like Figure 2 As shown, in the first specific embodiment, when the crystal driving circuit is used for a 32.768K crystal driving circuit:
[0041] A 32.768K crystal is connected between the external load terminals X0 and X1 of the crystal driver circuit; a 12pF load is connected to ground between the external load terminals X0 and X1; the control signal RF_SEL is sent through the register module to configure the resistance value of the feedback resistor module to 10Mohm; the bypass control signal BYP output by the register module is set to 0 to select the crystal oscillation mode, that is: turn off the trigger module BUFFER, turn on the oscillation circuit module, and make the second selector MUX2 select the oscillation signal of the output oscillation circuit module;
[0042] The register module sends a selection signal REG_SEL to select the low-frequency starter circuit to work, while simultaneously shutting down the mid-to-high-frequency starter circuit. Then, the register module sends a first start signal 32K_IOPSEL to configure a suitable 32.768K crystal oscillator start-up current. At this point, the crystal oscillator starts working, and the output module VOUT outputs a 32.768K clock signal.
[0043] like Figure 2 As shown in the second specific embodiment, when the crystal driving circuit is used for a medium-to-high frequency crystal driving circuit, a 32MHz crystal is used as an example:
[0044] A 32M crystal is connected between the external load terminals X0 and X1 of the crystal driver circuit; a 12pF load is connected to ground between the external load terminals X0 and X1; the control signal RF_SEL is sent through the register module to configure the resistance value of the feedback resistor module to 500Kohm; the bypass control signal BYP output by the register module is set to 0 to select the crystal oscillation mode, that is: turn off the trigger module BUFFER, turn on the oscillation circuit module, and make the second selector MUX2 select the oscillation signal of the output oscillation circuit module;
[0045] The register module sends a selection signal REG_SEL to select the medium- and high-frequency starter circuit to operate, while simultaneously shutting down the low-frequency starter circuit. Then, the register module sends a second start signal MF_IOPSEL to configure a suitable 32MHz crystal oscillator start-up current. At this point, the crystal oscillator starts working, and the output module VOUT outputs a 32MHz clock signal.
[0046] like Figure 2 As shown, in the third specific embodiment, when the chip system requires an external clock signal, i.e., crystal oscillator bypass mode:
[0047] Set the bypass control signal BYP output by the register module to 1 to select the external clock input mode. The bypass control signal BYP has a high priority. When it is 1, neither the low-frequency starter circuit nor the medium-to-high-frequency starter circuit will work.
[0048] When a clock signal is input from the external load terminal X0 of the crystal driver circuit, the crystal oscillator is not working. The clock output by the output module VOUT is equal to the clock input from the external load terminal X0. That is, when a 10MHz clock is input from the external load terminal X0, the output module VOUT also outputs a 10MHz clock.
[0049] In this mode, clock signal input of any frequency can be supported, which makes it easier to provide more clock frequency options for the chip system and increase the flexibility of the chip system.
[0050] It should be understood that the above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.
Claims
1. An ultra-wideband crystal driving circuit, characterized in that, Used to drive a 32.768kHz low-frequency crystal or a 4-32MHz medium-high frequency crystal, and output a low-frequency or medium-high frequency crystal oscillation signal; the crystal driving circuit includes a feedback resistor module, an oscillation circuit module, and a first selector; The feedback resistor module is connected to the oscillation circuit module, which is connected to the first selector, the external crystal, and the external load. The first selector is connected to the oscillation circuit module. The oscillation circuit module also includes a low-frequency oscillator sub-circuit and a medium-to-high-frequency oscillator sub-circuit, which are used to start the low-frequency crystal and the medium-to-high-frequency crystal, respectively. When an external crystal needs to be activated, the driving circuit connects the corresponding crystal according to the required clock frequency; a control signal is sent to the feedback resistor module to configure the resistance value of the feedback resistor module to the resistance value required to activate the crystal; a selection signal is sent to the oscillation circuit module to turn on one of the oscillator circuits in the oscillation circuit module while turning off the other oscillator circuit; the first selector outputs the selected crystal oscillation signal according to the selection signal; the resistance value of the feedback resistor module is in the range of 500 Kohm to 10 Mohm, and is dynamically adjusted according to the crystal frequency band. When starting the 32.768kHz low-frequency crystal, the resistance should be set to 10MΩ; when starting the 4-32MHz mid-to-high frequency crystal, the resistance should be set to 500KΩ~2MΩ.
2. The ultra-wideband crystal driving circuit according to claim 1, characterized in that, The driving circuit further includes an output module connected to the first selector, which is used to increase the driving capability of the crystal oscillation signal and output it.
3. The ultra-wideband crystal driving circuit according to claim 2, characterized in that, The driving circuit also includes a trigger module, which is connected to the output module and the external load terminal, and is used to send the externally input clock signal to the output module.
4. The ultra-wideband crystal driving circuit according to claim 3, characterized in that, The trigger module is a Schmitt trigger.
5. The ultra-wideband crystal driving circuit according to claim 3, characterized in that, The crystal driving circuit further includes a second selector, which is connected to the trigger module and the first selector, and is used to output the signal of the trigger module or the first selector.
6. The ultra-wideband crystal driving circuit according to claim 5, characterized in that, The driving circuit further includes a register module, which configures the control signal to adjust the resistance value of the feedback resistor module and configures the selection signal to select whether to turn on the low-frequency oscillator circuit or the medium-high frequency oscillator circuit; the register module is also configured with a first start signal or a second start signal to start the low-frequency oscillator circuit or the medium-high frequency oscillator circuit respectively.
7. The ultra-wideband crystal driving circuit according to claim 6, characterized in that, The register module also sends a bypass control signal to the trigger module, the oscillation circuit module, and the second selector to connect the external load terminals of the trigger module and the crystal drive circuit, turn off the oscillation circuit module, and enable the second selector to select the output external clock signal.
8. The ultra-wideband crystal driving circuit according to claim 1, characterized in that, The feedback resistor module includes multiple resistors connected in series, and each of the multiple series resistors is connected in parallel with a switch. The control signal is used to adjust the resistance value of the feedback resistor module by turning the control switch on or off.