CN118118012A - Crystal oscillator - Google Patents

Abstract

The invention provides a crystal oscillator, comprising: an oscillator; a system for controlling the frequency of an oscillator, wherein the system comprises: a plurality of temperature sensing circuits, wherein each of the plurality of temperature sensing circuits is configured to generate a temperature sensing signal, the temperature sensing signal corresponding to a temperature acquired by the each temperature sensing circuit, respectively; a reference signal generation circuit for generating a reference signal; a first curve function generating circuit coupled to the two or more temperature sensing circuits and the reference signal generating circuit, the first curve function generating circuit for providing two or more curve generating signals based on the temperature sensing signals and the reference signal; an adder circuit is coupled to the first curve function generating circuit for providing a first signal for controlling the frequency of the oscillator based on the two or more curve generating signals. By the invention, the stability of the performance of the crystal oscillator is improved.

Description

Crystal oscillator

Technical Field

The invention relates to the field of circuits, in particular to a crystal oscillator.

Background

Oscillators are widely used in digital and analog integrated circuits to generate critical clock signals. The oscillators may include crystal oscillators, voltage controlled crystal oscillators, and many other types of oscillators. Although a crystal oscillator may generally provide a relatively constant and accurate output frequency under fixed environmental conditions, the output frequency of the crystal oscillator may still vary as environmental conditions vary. Since oscillators are widely used in many circuit applications to generate critical clock signals, crystal oscillators can cause variations in output frequency due to variations in environmental conditions, resulting in poor operational accuracy of the crystal oscillator due to environmental effects.

Aiming at the problem that the working accuracy of the crystal oscillator is poor due to the influence of the environment caused by the change of the output frequency caused by the change of the environmental condition in the crystal oscillator in the related art, no effective solution is proposed at present.

Disclosure of Invention

The present disclosure provides a crystal oscillator.

According to one aspect of the invention, the crystal oscillator includes an oscillator; a system for controlling the frequency of the oscillator, wherein the system comprises: a plurality of temperature sensing circuits, wherein each of the plurality of temperature sensing circuits is configured to generate a temperature sensing signal corresponding to a temperature acquired by the each temperature sensing circuit; a reference signal generation circuit for generating a reference signal; a first curve function generating circuit coupled to the two or more temperature sensing circuits and the reference signal generating circuit, the first curve function generating circuit for providing two or more curve generating signals based on the temperature sensing signals and the reference signal; an adder circuit is coupled to the first curve function generating circuit for providing a first signal for controlling the frequency of the oscillator based on the two or more curve generating signals.

The crystal oscillator can realize that the temperature is not influenced by the change of the ambient temperature of the crystal controller, and the performance of the crystal oscillator is improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:

fig. 1 is a graph showing an exemplary relationship of two change signals and a sum of the two change signals with respect to a temperature change.

Fig. 2A is a block diagram illustrating an exemplary oscillator control circuit.

Fig. 3A is a schematic diagram of an exemplary embodiment of the oscillator control circuit shown in fig. 2A. .

Fig. 3B is a schematic diagram of an exemplary summing circuit.

Fig. 4A is a block diagram illustrating another exemplary oscillator control circuit.

Fig. 4B is a graph illustrating an exemplary relationship and temperature variation between output signals of the exemplary oscillator control circuit shown in fig. 4A.

Fig. 5A is a schematic diagram of an exemplary embodiment of the oscillator control circuit shown in fig. 4A.

Fig. 5B is a schematic diagram of another exemplary summing circuit.

Fig. 5C is a graph illustrating an exemplary current-temperature relationship corresponding to the current illustrated in fig. 5A. .

Fig. 6A is a schematic diagram of another exemplary embodiment of the oscillator control circuit shown in fig. 4A. .

Fig. 6B is a schematic diagram of another exemplary summing circuit.

Fig. 6C is a graph illustrating an exemplary current-temperature relationship corresponding to the current shown in fig. 6A. .

Fig. 7A is a block diagram illustrating an exemplary temperature compensated voltage controlled crystal oscillator (TC-VCXO) circuit.

Fig. 7B is a diagram illustrating an exemplary relationship and temperature variation between control signals of the exemplary TC-VCXO circuit shown in fig. 7A.

FIG. 8A is a schematic diagram of an exemplary temperature sensing circuit.

Fig. 8B is a graph illustrating an exemplary relationship and temperature variation between the temperature sensing voltages shown in fig. 8A.

Fig. 9 is a flow chart representing an exemplary method for controlling the frequency of an oscillator.

Detailed Description

It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.

FIG. 1 is a diagram of an embodiment of the present invention, including the steps of:

The implementation of the embodiments of the present invention will be described in detail below with reference to examples.

It should be noted that the steps illustrated in the flowcharts of the figures may be performed in a computer system such as a set of computer executable instructions, and that although a logical order is illustrated in the flowcharts, in some cases the steps illustrated or described may be performed in an order other than that illustrated herein.

Fig. 1 is a graph 100 showing an exemplary relationship of two change signals and a sum of the two change signals with respect to a change in temperature. The sum of the signals may be a voltage signal or a current signal. Using the current signal as an example, the graph 100 shows the first current I1 102, the second current I2 104, and the sum of the first current I1 102 and the second current I2 104, i.e. the total current I106. The first current I1 102 and the second current I1 104 the current I2 104 may represent curve-generated current signals generated, for example, in response to temperature-sensing signals. The temperature sensing signal, e.g., a temperature sensing voltage, may be generated in response to a change in temperature obtained by the temperature sensing circuit. The temperature sensing signal and circuitry are described in detail below.

As shown in fig. 1, the first current I1 102 is illustrated as a current curve that changes from a low value to a high value. The second current I2 104 is illustrated as a current curve that changes from a higher value to a lower value. The first current I1 102 and the second current I2 104 may be responsive to temperature changes. I.e. the horizontal axis of fig. 1 can represent temperature variations and the vertical axis can represent current variations corresponding to temperature variations. Moreover, the first current I1 102 and the second current I2 104 may be summed, added, or added to produce the added current I106.

As an example, the nonlinear curve function generating circuit may include two or more differential circuits. The differential circuit may have two input signals, a first input signal and a second input signal. The first input signal may be a reference voltage signal having a substantially constant voltage. The second input signal may be a varying voltage signal generated by the temperature sensing circuit in response to a temperature change, for example. Since the temperature changes sensed by different temperature sensing circuits may be different, different voltage signals may be generated. Thus, depending on the difference in voltage levels between the two input signals, the currents flowing through the different differential circuits (e.g., current I1 102 and current I2 104) may have different current levels and different current curves. The currents having the various current levels and the various current curves (e.g., current I1 102 and current I2 104) may then be added, summed, or superimposed to generate a nonlinear current (current I106) having higher order (e.g., third order) components. Exemplary nonlinear curve function generating circuits and linear curve function generating circuits are described in detail below.

Fig. 2A is a block diagram illustrating an exemplary oscillator control circuit 200. The oscillator control circuit 200 may include a first temperature sensing circuit 202, a second temperature sensing circuit 204, a reference signal generation circuit 206, and a curve function generation circuit 208. The oscillator control circuit 200 may also include other circuits, such as a voltage or current summing circuit (not shown in fig. 2A), which may sum, add, or superimpose two or more voltages or currents. It should be appreciated that the oscillator control circuit 200 may also include any other possible circuit elements.

In some embodiments, the first temperature sensing circuit 202 and the second temperature sensing circuit 204 may obtain temperature by, for example, sensing or detecting an ambient temperature change as their input signals. Based on the obtained temperature change, the first temperature sensing circuit 202 and the second temperature sensing circuit 204 may generate temperature sensing signals, such as temperature sensing voltages V1 203 and V2 205. The temperature sensing voltages V1 and V2 203 and 205 may vary in response to these variations. Temperatures obtained by the first temperature sensing circuit 202 and the second temperature sensing circuit 204, respectively. As a result, the temperature sensing voltages V1 and V2 205 may represent or substantially represent a change in temperature. An exemplary temperature sensing circuit is described in detail below with respect to fig. 2-7. Fig. 8A-8B. In some embodiments, to collect temperature conditions at different locations on an integrated circuit chip or device, one or more temperature sensing circuits, such as first temperature sensing circuit 202 and second temperature sensing circuit 204, may be placed at each location. In some embodiments, one or more temperature sensing circuits may be co-located.

As shown. As shown in fig. 2A, in some embodiments, the oscillator control circuit 200 may further include a reference signal generation circuit 206 that may generate a reference signal (e.g., reference voltage signal Vc 207) that is constant or substantially constant with respect to changes in environmental conditions, such as temperature changes. As an example, the reference signal generation circuit 206 may include a bandgap voltage reference generation circuit capable of providing a substantially constant reference voltage over a desired range of temperature variations. Further, the reference signal (e.g., reference voltage signal Vc 207) may have any desired value.

As shown. As shown in fig. 2A, in some embodiments, the oscillator control circuit 200 may also include a curve function generation circuit 208. The curve function generation circuit 208 receives input signals (e.g., temperature sensing voltages V1 and V2 205, and a reference voltage signal Vc 207) from the temperature sensing circuit. 202 and 204, and a reference signal generation circuit 206. After receiving the input signal, the curve function generating circuit 208 may compare, for example, the value of each of the temperature sensing voltages Vl 203 and V2 205 with the value of the reference voltage signal Vc 207. As an example, the curve function generation circuit 208 may compare both the temperature sensing voltages V1 203 and V2 205 with the reference voltage signal Vc 207 and generate the output signals Voutl and Vout2 210.

In some embodiments, the curve function generation circuit 208 may also provide two or more curve generated current signals (e.g., currents I1 a and I2 305B shown in fig. 3A) that may be added, summed, or superimposed to generate a sum current as described below. In some embodiments, the curve function generation circuit 208 may generate output signals (e.g., output signals Vout1 209 and Vout2 210) as voltage signals. In some embodiments, the curve function generation circuit 208 may generate the output signal as a current signal rather than a voltage signal. The curve function generating circuit 208 may also convert the output voltage signal to an output current signal and vice versa. The curve function generating circuit 208 is described in further detail below.

Fig. 2B is a graph 240 illustrating an exemplary relationship between output signals (e.g., output signal Vout 2210) of the exemplary oscillator control circuit 200 shown in fig. 2A. 2A and temperature change. In some embodiments, the output signal Vout2 is derived from or corresponds to a temperature change obtained by the first temperature sensing circuit 202 and the second temperature sensing circuit 204. Thus, the output signal Vout2210 may be used to control, e.g., compensate for, frequency variations of an oscillator (e.g., a voltage controlled oscillator, VCXO) caused by temperature variations. As shown. As shown in fig. 2B, the curve of the output signal Vout2210 may have higher order components, such as second and/or third order components. The higher order components may have an effect on the curve shape of the output signal Vout2 210. By adjusting the profile of the output signal Vout2210, the control voltage of the oscillator (e.g., VCXO) can be fine tuned and a better match can be provided to the frequency profile of the oscillator. Details of using the oscillator control circuit 200 to control the oscillator will be described below in connection with fig. 7A-7B.

Fig. 3A is a schematic diagram of an exemplary embodiment 300 of the oscillator control circuit 200 shown in fig. 2. 2A. Those of ordinary skill in the art will readily appreciate that the blocks and circuit elements shown in fig. 1 are understood. The embodiment in fig. 3A may vary their number or their relative configuration. The exemplary embodiment 300 may also include additional blocks or circuit elements.

As shown, referring to fig. 3A, an exemplary embodiment 300 may include a first temperature sensing circuit 202 and a second temperature sensing circuit 204; a reference signal generation circuit 206; and differential circuits 320A and 320B. The differential circuits 320A and 320B may be included in the curve function generating circuit 208 shown in fig. 2. 2A. In the figure. As shown in fig. 3A, the first and second temperature sensing circuits 202 and 204 and the reference signal generation circuit 206 may be similar or substantially similar to those described with respect to fig. 2. Is identical to fig. 2A and is therefore not described here.

As shown in fig. 3A, in some embodiments, differential circuit 320A may include a power supply 301A, a current source 302A, one or more (e.g., two) resistors R1A and R2 306A, and one or more (e.g., two) transistor devices M1 308A and M1 308A. M2 310A. Similarly, differential circuit 320B may include power supply 301B, current source 302B, resistors R3B 304 and R4 306B, and transistor devices M3 308B and M4 310B.

Those of ordinary skill in the art will readily appreciate that the number of circuit elements, such as resistors and transistors, may be any number and is not limited to the number shown in fig. 1. 3A. The transistor devices (e.g., M1 308A, M, 310, A, M, 308B and M4, 310B) may be p-type devices or n-type devices, such as p-type metal oxide semiconductor (PMOS) or n-type metal oxide semiconductor. An oxide semiconductor (NMOS) device. The transistor devices may also have the same or different dimensions, including transistor width and length.

As shown in fig. 3A, in differential circuit 320A, power supply 301A may be electrically coupled to current source 302A. The power supply 301A may provide power to the differential circuit 320A. The voltage of the power supply 301A may vary depending on the application. The current source 302A may provide a constant or substantially constant current. In some embodiments, current source 302A may include a large-sized transistor device controlled by a feedback circuit (not shown) such that the output current of the current source may remain substantially constant.

As shown in fig. 3A, the differential circuit 320A may include a left leg including a resistor R1304A and a transistor device M1 308A, and a right leg including a resistor R2 306A and a transistor device M2 310A. One end of resistor R1304A and one end of resistor R2 306A are electrically coupled to current source 302A. And the other terminals of resistor R1304A and resistor R2 306A are electrically coupled to terminals, e.g., source terminals, of transistor devices M1 308A and M2 310A (shown as p-type transistor devices in fig. 3A), respectively. Since current source 302A is electrically coupled to the left and right legs of differential circuit 320A, current I x1 provided by current source 302A is divided between the left and right legs. That is, the sum of the currents flowing through the left and right branches is equal to or substantially equal to the current I1 provided by the current source 302A.

As shown in fig. 3A, transistor device M1 308A includes a gate terminal electrically coupled to first temperature sensing circuit 202. Accordingly, the gate terminal of the transistor device M1 308A is controlled by the temperature sensing voltage V1 203 generated by the first temperature sensing circuit 202. The gate terminal of the gate terminal transistor device M2 310A is electrically coupled to the reference signal generating circuit 206. Accordingly, the gate terminal of the transistor device M2 310A receives the reference voltage signal Vc 207 generated by the reference signal generation circuit 206. As described above, the reference voltage signal Vc 207 may be constant or substantially constant.

In some embodiments, if the temperature sensing voltage V1 203 and the reference voltage signal Vc 207 are different, the transistor devices M1308A and M2 310A are in different operating conditions because they receive different control voltages at their gate terminals. As a result, the current flowing through transistor device M1308A (i.e., the left branch) and the current flowing through transistor device M2 310A (i.e., the right branch) may be different. As an example, if the value of the temperature sensing voltage V1 203 is less than the value of the reference voltage signal Vc 207, the current flowing through the transistor device M1308A may be greater than the current flowing through the transistor device M2 310A. Thus, if transistor devices M1308A and M2A are PMOS devices, transistor device M1308A may have a greater gate-to-source voltage than transistor device M2 310A. On the other hand, if transistor devices M1308A and M2 a are NMOS devices, transistor device M1308A may have a smaller gate-to-source voltage than transistor device M2 310A. Accordingly, because the currents flowing through the left and right branches of the differential circuit 320A may be different, the voltage levels of the output signal Vout1 209A associated with the left branch and the output signal Vout2 210A associated with the right branch may also be different.

As described above, differential circuit 320B may include power supply 301B, current source 302B, resistors R3B 304B and R4 306B, and transistor devices M3 308B and M4 310B. The differential circuit 320B may have a similar or substantially similar configuration as the differential circuit 320A. For example, the differential circuit 320B receives the temperature-sensing voltage V2 205 from the second temperature-sensing circuit 204 through the transistor device M4B in its right branch; and receives the reference voltage signal Vc 207 generated by the reference signal generating circuit 206 through the transistor device M3 308B in its left branch. The operation of the differential circuit 320B may be the same as or similar to that of the differential circuit 320A, and thus will not be described in detail herein. The differential circuit 320B may generate the output signal Vout1 209B and the output signal Vout2 210B. Because the currents flowing through the left and right branches of the differential circuit 320B may be different, the voltage levels of the output signal Vout1 209B associated with the left branch and the output signal Vout2 210B associated with the right branch may also be different.

As shown in the figure. Fig. 3B is a schematic diagram of an exemplary summing circuit 340. As described above, the output signals Vout1 209A/B and Vout2 210A/B (shown in FIG. 3A) may be voltage signals. In some applications, the output signals Vout1 209A/B and Vout2 210A/B may need to be converted from voltage signals to current signals. Thus, in some embodiments, one or more instances of summing circuit 340 may be coupled to differential circuits 320A and 320B or integrated with differential circuits 320A and 320B. As an example, resistors 318A and 318B in summing circuit 340 may be electrically coupled to differential circuit 320A and similarly coupled to differential circuit 320B. Specifically, resistors 318A and 318B may be coupled to output signal Vout1 a and output signal Vout 2a, respectively, for converting output signal Vout1 209A and output signal Vout 2a from a voltage signal to a current signal. In some embodiments, in summing circuit 340, one end of resistor 318A and one end of resistor 318B may be electrically coupled to electrical ground. The other terminals of the resistor 318A and the resistor 318B may be electrically coupled to the output signal Vout1 209A and the output signal Vout 2a, respectively. Similarly, one or more instances of summing circuit 340 may also be electrically coupled to differential circuit 320B. As a result, the output voltage signals Vout1 209A/B and Vout2 a/B may be converted to current signals using one or more instances of the summing circuit 340. It should be appreciated that summing circuit 340 may also be any other desired summing circuit.

Referring to fig. 3A and 3B, in some embodiments, summing circuit 340 may also add, sum, or superimpose the current signals. As an example, one or more instances of summing circuit 340 may be coupled to output signal Vout 2a and output signal Vout 2B through terminals of resistor 318B. As a result, the currents flowing through the two right branches of differential circuits 320A and 320B (i.e., current I1 a and current I2 305B) may be summed, added, or added to generate a sum current (e.g., sum current I317 flowing through differential circuits 320A and 320B). Resistor 318B). As described above, the current I1 a and the current I2B may have different values and curves. As an example, in some embodiments, the transistor devices and resistors in differential circuits 320A and 320B may be different in size such that the same temperature sensing voltages V1 203 and V2 205 may generate different currents I1 a and I2305B. As another example, in some embodiments, differential circuits 320A and 320B receive different temperature sensing voltages V1 and V2 205 and thus generate different currents I1 305A and I2305B.

The currents I1A and I2B may also be linear or non-linear. The currents I1 a and I2 305B may each be at different levels such that coarse and/or fine adjustments of the total current I317 may be achieved. As an example, the current I1 305A may be at a high level such that it represents a coarse adjustment. That is, adjusting current I1A may cause a relatively large change in total current I317. On the other hand, the current I2B may be at a low level, so that it represents a fine tuning. That is, adjusting current I2B may cause relatively small changes in total current I317.

Further, because the total current I317 originates from or corresponds to the temperature change obtained by the first temperature sensing circuit 202 and the second temperature sensing circuit 204, the total current I317 may be used to control or compensate for the temperature change due to. As described above, the curve of the total current I317 may have a higher order component, such as a third order component. The higher order components may have an effect on the shape of the curve of the sum current I317. Thus, by adjusting the shape of the curve of the sum current I317, a better match to the frequency curve of the oscillator can be provided.

Fig. 4A shows a block diagram of another exemplary oscillator control circuit 400. The oscillator control circuit 400 may include a first temperature sensing circuit 402, a second temperature sensing circuit 404, a third temperature sensing circuit 406, a reference signal generation circuit 408, and a graph. Function generation circuit 410. The oscillator control circuit 400 may also include other circuits, such as a summing circuit (not shown in fig. 4A), which may generate a sum of voltages of the currents. It should be appreciated that the oscillator control circuit 400 may also include any other desired circuit elements.

The first temperature sensing circuit 402, the second temperature sensing circuit 404, the third temperature sensing circuit 406, and the reference signal generating circuit 408 may be the same as or similar to the temperature sensing circuit and the reference signal generating circuit shown in fig. 4. Is identical to fig. 2A and is therefore not described here. Based on the respective temperature changes, the first, second, and third temperature sensing circuits 402, 404, and 406 may generate output signals such as temperature sensing voltages V1 403, V2 405, and V3 407. The temperature sensing voltages V1, V2, 405, and V3 407 may vary in response to variations in temperatures obtained by the first, second, and third temperature sensing circuits 402, 404, and 406, respectively. As a result, the temperature sensing voltages V1 403, V2 405, and V3 407 may represent or substantially represent the change in the obtained temperature. Exemplary temperature sensing circuits are described in detail below with respect to fig. 8A-8B.

The curve function generation circuit 410 may receive input signals (e.g., temperature sensing voltages V1 403, V2 405, and V3 407, and a reference voltage signal Vc 409) from the first temperature sensing circuit 402, the second temperature sensing circuit 404, and the third temperature sensing circuit 406. And a reference signal generation circuit 408. After receiving the input signal, the curve function generation circuit 410 may compare, for example, the value of each of the temperature sensing voltages V1 403, V2 405, and V3 407 with the value of the reference voltage signal Vc. 409. As an example, the curve function generating circuit 410 compares all the temperature sensing voltages V1 403, V2 405, and V3 407 with the reference voltage signal Vc 409 and generates the output signals Voutl 412 and Vout2 414.

In some embodiments, the curve function generation circuit 410 may also generate one or more (e.g., three) current signals (current signals I1 505A, I, 505B and I3 505C) shown in fig. 5. 5A) They are added, summed or added together to generate the total current described below. In some embodiments, the curve function generation circuit 410 generates the output signals as voltage signals (e.g., output signals Vout1 412 and Vout2 414). In some embodiments, the curve function generation circuit 410 may generate the output signal as a current signal rather than a voltage signal. The curve function generation circuit 410 may also convert the output voltage signal to an output current signal and vice versa. The curve function generation circuit 410 is described in further detail below.

Fig. 4B is a graph 440 illustrating an exemplary relationship between output signals (e.g., output signal Vout 2414) of the exemplary oscillator control circuit 400 illustrated in fig. 4A. 4A and temperature change. In some embodiments, the output signal Vout2414 is derived from or corresponds to temperature changes obtained by the first temperature sensing circuit 402, the second temperature sensing circuit 404, and the third temperature sensing circuit 406. Thus, the output signal Vout2414 may be used to control (e.g., compensate for) frequency variations of an oscillator (e.g., VCXO) caused by temperature variations. As shown. As shown in fig. 4B, the curve of the output signal Vout2414 may have higher order components, such as second and/or third order components. The higher order components may have an effect on the curve shape of the output signal Vout2 414. By adjusting the profile of the output signal Vout2414, the control voltage of the oscillator (e.g., VCXO) can be fine tuned and a better match can be provided to the frequency profile of the oscillator.

Fig. 5A is a schematic diagram of an exemplary embodiment 500 of the oscillator control circuit 400 shown in fig. 4. 4A. Those of ordinary skill in the art will readily appreciate that the blocks and circuit elements shown in fig. 1 are understood. The embodiment in fig. 5A may vary their number or their relative configuration. The exemplary embodiment 500 may also include additional blocks or circuit elements.

Referring to fig. 5A, an exemplary embodiment 500 may include first, second, and third temperature sensing circuits 402, 404, and 406, a reference signal generating circuit 408, and differential circuits 520A, 520B, and 520C. The differential circuits 520A, 520B, and 520C may be included in the curve function generating circuit 410 shown in fig. 4. 4A. In the figure. Referring to fig. 5A, the first, second, and third temperature sensing circuits 402, 404, and 406 and the reference signal generating circuit 408 may be similar or substantially similar to those described with respect to fig. 4. Is identical to fig. 2A and is therefore not described here.

As shown. As shown in fig. 5A, in some embodiments, the differential circuit 520A/B/C may include a power supply 501A/B/C, a current source 502A/B/C, one or more resistors R1 504A, R2 506A, R3 504B, R4 506B, R5 504C, and R6 506C, and one or more transistor devices M1 508A, M510A, M3 508B, M4B, M5C and M6 510C. Those of ordinary skill in the art will readily appreciate that the number of circuit elements, such as resistors and transistor devices, may be any number and is not limited to the number shown in fig. 5A. The transistor devices (e.g., M1 508A and M2 510A) may be p-type devices or n-type devices, such as PMOS or NMOS devices. The transistor devices may also have the same or different dimensions, including transistor width and length.

Further, referring to fig. 5A, the circuit configuration of the differential circuit 520A/B/C, including the power supply 501A/B/C, the current source 502A/B/C, the resistors R1 504A, R2 506A, R3 504B, R506B, R5C and R6 506C, and the transistor devices M1 508A, M2 510A, M3 508B, M4 510B, M5C and M6 510C may be substantially the same as or similar to the transistor devices of the differential circuit 320A/B described above, and thus will not be described again. However, the parameters of the circuit elements in fig. 1 may be varied. The dimensions of the corresponding elements shown in fig. 5A, e.g., transistor devices, may be the same as or different from the corresponding elements shown in fig. 3A. .

As shown. As shown in fig. 5A, in some embodiments, transistor devices M1 a and M3 508B may include gate terminals electrically coupled to first temperature sensing circuit 402 and second temperature sensing circuit 404, respectively. As a result, the gate terminals of the transistor devices M1 508A and M3 508B are controlled by the temperature sensing voltages V1 403 and V2 405 generated by the first temperature sensing circuit 402 and the second temperature sensing circuit 404, respectively. The gate terminals of transistor devices M2 510A and M4 510B are electrically coupled to reference signal generation circuit 408. Thus, the gate terminals of the transistor devices M2 510A and M4 510B receive the reference voltage signal Vc 409 generated by the reference signal generation circuit 408. As described above, the reference voltage signal Vc 409 may be constant or substantially constant.

In some embodiments, differential circuit 520C receives temperature-sensing voltage V3 407 from temperature-sensing circuit 406 through the gate terminal of transistor device M6 510C in the right branch of differential circuit 520C. The differential circuit 520C also receives the reference voltage signal Vc 409 provided by the reference signal generating circuit 408 through the gate terminal of the transistor device M5C in the left branch of the differential circuit 520C. It will be appreciated by those of ordinary skill in the art that the circuit configuration of the differential circuit 520A/B/C may also be of any other type such that it is capable of comparing the temperature sensing voltages V1 403, V2 405, and V3 407 with a reference voltage. Voltage signal Vc 409.

In some embodiments, if the temperature sensing voltage V1 403 and the reference voltage signal Vc 409 are different, the transistor devices M1 508A and M2 a are in different operating conditions because they receive different control voltages at their gate terminals. As a result, the current flowing through transistor device M1 508A and the current flowing through transistor device M2 510A may be different. As an example, if the temperature sensing voltage V1 403 has a value less than the reference voltage signal Vc 409, the current flowing through the transistor device M1 508A may be greater than the current flowing through the transistor device M2 510A. Thus, if transistor devices M1 a and M2 a are PMOS devices, transistor device M1 508A may have a greater gate-to-source voltage than transistor device M2 510A. On the other hand, if transistor devices M1 508A and M2 a are NMOS devices, transistor device M1 508A may have a smaller gate-to-source voltage than transistor device M2 510A. Accordingly, because the currents flowing through the left and right branches of the differential circuit 520A may be different, the voltage levels of the output signal Vout1 512A associated with the left branch and the output signal Vout2 514A associated with the right branch may also be different.

As shown in fig. 5A, the differential circuit 520B may have a similar or substantially similar configuration as the differential circuit 520A. For example, the differential circuit 520B receives the temperature-sensing voltage V2 405 from the second temperature-sensing circuit 404 through the transistor device M3 508B in its left leg; and receives the reference voltage signal Vc 409 generated by the reference signal generating circuit 408 through the transistor device M4B in its right branch. The operation of the differential circuit 520B may be the same as or similar to the differential circuit 520A, and thus will not be described in detail herein. The differential circuit 520B may generate the output signal Vout1 512B and the output signal Vout2 514B. Because the currents flowing through the left and right branches of the differential circuit 520B may also be different, the voltage levels of the output signal Vout1 512B associated with the left branch and the output signal Vout2 514B associated with the right branch may also be different.

The differential circuit 520C may have a similar or substantially similar configuration as the differential circuit 520A/B. For example, the differential circuit 520C receives the temperature sensing voltage V3407 from the third temperature sensing circuit 406 through the transistor device M6C in its right branch; and receives the reference voltage signal Vc 409 generated by the reference signal generating circuit 408 through the transistor device M5C in its right branch. The operation of the differential circuit 520C may be the same as or similar to the operation of the differential circuit 520A/B and thus will not be described here. The differential circuit 520C may generate the output signal Vout1 512C and the output signal Vout2 514C. Because the currents flowing through the left and right branches of the differential circuit 520C may be different, the voltage levels of the output signal Vout1 512C associated with the left branch and the output signal Vout2 514C associated with the right branch may also be different.

As shown in the figure. Fig. 5B is a schematic diagram of another exemplary summing circuit 540. As described above, the output signals Vout1 512A/B/C and Vout2 514A/B/C (shown in FIG. 5A) may be voltage signals. In some applications, the output signals Vout1 512A/B/C and Vout2 514A/B/C may need to be converted from voltage signals to current signals. Thus, in some embodiments, one or more instances of summing circuit 540 may be coupled to differential circuit 520A/B/C or integrated with differential circuit 520A/B/C. As an example, differential circuit 520A and similar differential circuits 520B and 520C may be coupled to resistors 518A and 518B of summing circuit 540. Specifically, resistors 518A and 518B may be coupled to output signal Vout1 512A and output signal Vout2 514A, respectively, for converting the voltage signal to a current signal. In some embodiments, in summing circuit 540, one end of resistor 518A and one end of resistor 518B may be electrically coupled to electrical ground. The other terminals of the resistor 518A and the resistor 518B may be electrically coupled to the output signal Vout1 512A and the output signal Vout2 514A, respectively. Similarly, one or more instances of summing circuit 540 may also be coupled to differential circuits 520B and 520C. As a result, the output voltage signals Vout1 512A/B/C and Vout2 514A/B/C may be converted to current signals using one or more instances of the summing circuit 540. It should be appreciated that summing circuit 540 may also be any other desired summing circuit.

Referring to fig. 5A and 5B, in some embodiments, summing circuit 540 may also add, sum, or superimpose the current signals. As an example, one or more instances of summing circuit 540 may be coupled to output signals Vout2 514A, vout2 514B and Vout2 514C through terminals of resistor 518B. As a result, the currents flowing through the right branch of the differential circuits 520A, 520B, and 520C (e.g., current I1 505A associated with the output signal Vout2 514A, current I2 505B associated with the output signal Vout2 514B, and current I3 505C associated with the output signal Vout2 514B) Vout2 514C may be summed, added, or added to generate a total current (e.g., total current I517 flowing through resistor 518B). The currents I1 505A, I505B and I3 505C may be the same or different. As an example, in some embodiments, the transistor devices and resistors in the differential circuits 520A, 520B, and 520C may be different in size, such that the same input voltage may generate different currents I1 505A, I505B and I3 505C. As another example, in some embodiments, differential circuits 520A, 520B, and 520C receive different temperature-sensing voltages V1 403, V2 407, and V3 407 and thus generate different currents I1 505A, I2 505B and I3 505C.

Fig. 5C is a graph illustrating an exemplary current-temperature relationship corresponding to currents I1 505A, I, 505B and I3 505C. As shown. As shown in fig. 5C, the currents I1 505A, I B and I3 505C may be linear or non-linear. The currents I1 505A, I505B and I3 505C may be at different levels such that coarse and/or fine adjustments of the total current I517 may be provided. As an example, the current I1 505A may be at the highest level such that it represents the coarsest adjustment. That is, adjusting current I1 505A may cause a relatively large change in total current I517. On the other hand, the current I3 505C may be at the lowest level, so that it represents the finest regulation. That is, adjusting current I3 505C may cause a minimal change in total current I517. The current I2 505B may be at an intermediate level between the currents I1 505A and I3 505C. Thus, regulating current I2 505B may cause a moderate change in total current I517.

Further, because the total current I517 originates from or corresponds to the temperature changes sensed by the first, second, and third temperature sensing circuits 402, 404, and 406, the total current I517 may be used to control or compensate for frequency changes. An oscillator due to temperature variations. In some embodiments, the first, second, and third temperature sensing circuits 402, 404, and 406 may generate different currents I1505A, I, 505B, and I3 505C in response to the same or different temperature changes. In addition, the curves of currents I1505A, I, 505B and I3, 505C may have higher order components, such as third order components. As a result, the total current I517 may also have a higher order component, such as a third order component. Higher order components may have an effect on the curve shape of the total current I517. Further, since the currents I1505A, I, 505B and I3 505C correspond to the three temperature sensing circuits shown in fig. 5. As shown in fig. 5A, an additional degree of freedom for adjusting the total current I517 may be provided as compared to the degree of freedom for adjusting the total current I317 as shown in fig. 3. See fig. 3A, where two temperature sensing circuits are used. By adjusting the current level of the total current I517 and the additional degrees of freedom of the current profile, an improved fine tuning of the oscillator (e.g. VCXO) control voltage and a better matching to the oscillator frequency profile may be provided.

Fig. 6A is a schematic diagram of another exemplary embodiment 600 of the oscillator control circuit 400 shown in fig. 4. 4A. Those of ordinary skill in the art will readily appreciate that the blocks and circuit elements shown in fig. 1 are understood. The embodiment in fig. 6A may vary their number or their relative configuration. The exemplary embodiment 600 may also include additional blocks or circuit elements.

As shown in fig. 6A, an exemplary embodiment 600 may include first, second, and third temperature sensing circuits 402, 404, and 406; a reference signal generation circuit 408; and one or more (e.g., four) differential circuits 620A, 620B, 620C, and 620D. The differential circuits 620A, 620B, 620C, and 620D may be included in the curve function generating circuit 410 shown in fig. 4. 4A. In the figure. Referring to fig. 6A, the first, second, and third temperature sensing circuits 402, 404, and 406 and the reference signal generating circuit 408 may be similar or substantially similar to those described with respect to fig. 4. Is identical to fig. 2A and is therefore not described here.

Referring to FIG. 6A, in some embodiments, differential circuit 620A/B/C/D may include circuit elements similar to those shown in differential circuit 520A/B/C in FIG. 5. 5A. For example, the differential circuit 620A/B/C/D may include, among other things, one or more transistor devices M1 608A, M610A, M3 608B, M4 610B, M5 608C, M6C, M7 608D and M8 610D. Those of ordinary skill in the art will readily appreciate that the number of circuit elements, such as resistors and transistors, may be any number and is not limited to the number shown in fig. 1. 6A. The transistor devices (e.g., M1 608A and M2 610A) may be p-type devices or n-type devices, such as PMOS or NMOS devices. The transistor devices may also have the same or different dimensions, including transistor width and length. In the figure. As shown in fig. 6A, the circuit configuration of the differential circuit 620A/B/C/D may be substantially the same as or similar to the circuit configuration of the differential circuit 520A/B/C described above, and thus will not be described here. However, the parameters of the circuit elements in fig. 1 may be varied. The dimensions of the corresponding elements shown in fig. 6A, e.g., transistor devices, may be the same as or different from the corresponding elements shown in fig. 5A.

As shown in fig. 6A, in some embodiments, transistor devices M1 a and M3 608B may include gate terminals electrically coupled to first temperature sensing circuit 402 and second temperature sensing circuit 404, respectively. As a result, the gate terminals of the transistor devices M1 608A and M3 608B are controlled by the temperature sensing voltages V1 403 and V2 405 generated by the first temperature sensing circuit 402 and the second temperature sensing circuit 404, respectively. The gate terminals of transistor devices M2 610A and M4 610B are electrically coupled to reference signal generation circuit 408. Accordingly, the gate terminals of the transistor devices M2 610A and M4 610B receive the reference voltage signal Vc 409 generated by the reference signal generation circuit 408. As described above, the reference voltage signal Vc 409 may be constant or substantially constant.

In some embodiments, differential circuits 620C and 620D receive temperature sensing voltage V3 407 from temperature sensing circuit 406 through the gate terminal of transistor device M5 608C in the left branch and the gate terminal of transistor device M8D in the right branch of differential circuit 620C. Differential circuit 620D. The differential circuits 620C and 620D also receive the reference voltage signal Vc 409 generated by the reference signal generation circuit 408 through the gate terminal of the transistor device M6C in the right branch of the differential circuit 620C and the gate terminal of the transistor device M7D in the left branch of the differential circuit 620C. And a differential circuit 620D. It will be appreciated by those of ordinary skill in the art that the circuit configuration of the differential circuit 620A/B/C/D may also be of any other type such that it is capable of comparing the temperature sensing voltages V1 403, V2 405, and V3 407 with the reference voltage signal Vc 409.

The differential circuits 620A and 620B may operate in substantially the same or similar manner as described above with respect to the differential circuits 520A and 520B, for example, comparing the temperature sensing voltages V1 403 and V2 405 with the reference voltage signal Vc 409. The differential circuits 620C and 620D may also operate in substantially the same or similar manner as described above with respect to the differential circuits 520A and 520B, for example, comparing the temperature-sensing voltage V3 407 with the reference voltage signal Vc 409. Therefore, the operation of the differential circuit 620A/B/C/D will not be described here. Similar to the above, the differential circuit 620A/B/C/D may generate the output signal Vout1 612A/B/C/D and the output signal Vout2 614A/B/C/D. Since the current flowing through the left and right branches of either of the differential circuits 620A/B/C/D may be different, the voltage level of the output signal Vout1 612A/B/C/D may be different from the corresponding output signal Vout2 614A/B/C/D.

Fig. 6B is a schematic diagram of another exemplary summing circuit 640. As described above, the output signals Vout1612A/B/C/D and Vout2614A/B/C/D (shown in FIG. 6A) may be voltage signals. In some applications, the output signals Vout1612A/B/C/D and Vout2614A/B/C/D may need to be converted from voltage signals to current signals. Thus, in some embodiments, one or more instances of summing circuit 640 may be coupled to differential circuit 620A/B/C/D or integrated with differential circuit 620A/B/C/D. As an example, differential circuit 620A and similar differential circuits 620B, 620C, and 620D may be coupled to resistors 618A and 618B. In particular, resistors 618A and 618B may be coupled to the output signal Vout 1a and the output signal Vout2614A, respectively, for converting the voltage signal to a current signal. In some embodiments, in summing circuit 640, one end of resistor 618A and one end of resistor 618B may be electrically coupled to electrical ground. The other terminals of the resistor 618A and the resistor 618B may be electrically coupled to the output signal Vout 1a and the output signal Vout2614A, respectively. Similarly, one or more instances of summing circuit 640 may also be coupled to differential circuits 620B, 620C, and 620D. As a result, the output voltage signals Vout1 a/B/C/D and Vout2614A/B/C/D may be converted to current signals using one or more instances of the summing circuit 640. It should be appreciated that summing circuit 640 may also be any other summing circuit as desired.

Referring to fig. 6A and 6B, in some embodiments, summing circuit 640 may also add, sum, or superimpose the current signals. As an example, one or more instances of summing circuit 640 may be coupled to output signals Vout2 614A, vout2 614B, vout 614C and Vout2 614D through terminals of one or more instances of resistor 618B. As a result, the currents flowing through the right leg of the differential circuits 620A, 620B, 620C, and 620D (e.g., current I1 a associated with output signal Vout2 614A, current I2 605B associated with output signal Vout2 614B, current I3 605C associated with output signal Vout2 614B) signal Vout2 6140 and current I4 605D associated with output signal Vout2 614D may be summed, added, or added to generate a total current (e.g., total current I617 flowing through resistor 618B). Further, the currents I1 605A, I2 605B, I605C and I4 605D may be the same or different. As an example, in some embodiments, the transistor devices and resistors in the differential circuits 620A, 620B, 620C, and 620D may be different in size, such that the same input voltage may generate different currents I1 605A, I2 605B, I605C and I3 605C. I4 605D. As another example, in some embodiments, differential circuits 620A, 620B, 620C, and 620D may receive different temperature sensing voltages V1 403, V2 405, and V3 407, and may generate different currents I1 605A, I2 605B, I3C and I4 605D.

Fig. 6C is a graph 660 illustrating an exemplary current-temperature relationship corresponding to currents I1 605A, I2 605B, I605C and I4 605D. As shown. As shown in fig. 6C, the currents I1 605A, I2 605B, I605C and I4 605D may be linear or nonlinear. The currents I1 605A, I2 605B, I3C and I4 605D may be at different levels such that coarse and/or fine adjustments of the total current I617 may be provided. As an example, the current I1 605A may be at the highest level such that it represents the coarsest adjustment. That is, adjusting current I1 605A may cause the maximum change in total current I617. On the other hand, the current I4 605D may be at the lowest level, so that it represents the finest regulation. That is, adjusting current I4 605D may cause a minimal change in total current I617. The currents I2B and I3 605C may be at an intermediate level between the currents I1 a and I4 605C. Thus, adjusting currents I2B and I3 605C may cause a moderate level of change with current I617.

Further, because the total current I617 is derived from or corresponds to the temperature changes sensed by the first, second, and third temperature sensing circuits 402, 404, and 406, the total current I617 may be used to control or compensate for frequency changes. An oscillator due to temperature variations. In some embodiments, the first, second, and third temperature sensing circuits 402, 404, and 406 may generate different currents I1605A, I2 605B, I3C and I4 605D corresponding to the same or different temperature changes. Furthermore, the curves of the currents I1605A, I2 605B, I605C and I4 605D may have higher order components, such as third order components. As a result, the total current I617 may also have higher order components, such as third order components. The higher order components may have an effect on the shape of the curve of the total current I617. Further, since the currents I1605A, I2 605B, I605C and I4 605D correspond to the four temperature sensing circuits shown in fig. 6, the currents I605A, I2 605B, I605C and I4 605D can be corresponding to the four temperature sensing circuits shown in fig. 6. As shown in fig. 6A, an additional degree of freedom for adjusting the level and curve of the current I617 is provided in comparison to the degree of freedom provided by the embodiment 500 of the oscillator control circuit 400 shown in fig. 4. See fig. 5A, where three temperature sensing circuits are used. By adjusting the current level of the total current I617 and the additional degrees of freedom of the current profile, the fine tuning of the control voltage of the oscillator (e.g. VCXO) and a better matching to the frequency profile of the oscillator can be further improved.

Fig. 7A is a block diagram illustrating an exemplary temperature compensated voltage controlled crystal oscillator (TC-VCXO) circuit 700. Referring to fig. 7A, one of ordinary skill in the art will readily appreciate that the number of blocks and circuit elements shown, or their relative configurations, may vary. The TC-VXCO circuit 700 may also include additional blocks or circuit elements.

As shown in fig. 7A, the TC-VCXO circuit 700 may include a first curve function generation circuit 702, a second curve function generation circuit 704, an adder 710, and a voltage controlled crystal oscillator (VCXO) 714. As shown in fig. 7A, the first curve function generating circuit 702 may be the curve function generating circuit described above in fig. 1 and 2 (e.g., curve function generating circuits 208 and 410) and any of its various embodiments. See fig. 2A, 3A, 4A, 5A and 6A. Thus, the first curve generation circuit 702 may generate a voltage or current signal (e.g., signal S1) that represents the temperature change obtained by the temperature sensing circuits (e.g., the first, second, and third temperature sensing circuits 402, 404, and 406). In fig. 6A). The curve of the signal S1 may have higher order (e.g. third order) components. The first curve function generating circuit 702 may also be any of the variations or modifications of the curve function generating circuits described above in fig. 2A, 3A, 4A, 5A, and 6A and various embodiments thereof.

As shown in fig. 7A, the second curve function generating circuit 704 may be any type of circuit capable of generating a linear voltage or current signal (e.g., signal S2) with respect to temperature changes. The signal S2 may be, for example, a signal that has a linear relationship with its input signal over part or the whole of the input signal. As an example, similar to the first curve function generating circuit 702, the input signal of the second curve function generating circuit 704 may be a temperature sensing signal generated from a temperature sensing circuit. The output signal of the second curve function generating circuit 704 may be a voltage or current signal that varies with a constant slope in response to the input temperature sensing signal. In some embodiments, the second curve function generating circuit 704 may be an inverting amplifier that receives input signals from one or more temperature sensing circuits.

As shown in fig. 7A, adder 710 may be any type of digital or analog circuit that performs addition, summation, or superposition of input signals of adder 710. For example, adder 710 may be a mixer, a summing op-amp, a cross-linear amplifier, or an amplifier. Adder 710 may add, sum, or superimpose the input signals of one or more voltage signals or current signals (e.g., signals S1 and S2) and generate a corresponding output voltage or current signal (e.g., VCTC 712,712). ). The curve of VCTC 712 may have, for example, a desired curve and voltage level such that VCTC 712 may be provided as a control voltage for controlling the frequency of an oscillator (e.g., VCXO 714). By using VCTC 712,712 as the control voltage, a better match to the frequency curve of the oscillator can also be provided.

Fig. 7B is a diagram 740 illustrating an exemplary relationship between VCTC and 712 shown in fig. 7B. Fig. 7A and temperature variation. As shown. As shown in fig. 7B, VCTC may have any profile necessary to provide control and matching of the oscillator frequency profile.

As shown in fig. 7A, the VCXO 714 may be, for example, a crystal oscillator with a voltage controlled capacitor. Being supplied with a control voltage (e.g., VCTC 712,712), the VCXO 714 may partially or substantially adjust (e.g., tune) the temperature dependence of the resonant frequency of the crystal oscillator of the VCXO 714. That is, VCTC may be supplied to VXCO 714 to control or compensate for frequency variations of the crystal oscillator of the VCXO 714. For example, the frequency change of the crystal oscillator caused by the temperature change may be compensated for by applying an appropriate control voltage VCTC 712, which is then multiplied by the gain of the crystal oscillator so that the frequency of the crystal oscillator may be increased or decreased to a desired value.

Fig. 8A illustrates an exemplary temperature sensing circuit 800. Referring to fig. 8A, one of ordinary skill in the art will readily appreciate that the number of blocks and circuit elements shown, or their relative configurations, may vary. The temperature sensing circuit 800 may also include additional blocks or circuit elements. Temperature sensing circuit 800 may be included in temperature sensing circuits 202 and 204 in fig. 2A and 3A, for example. And temperature sensing circuits 402, 404, and 406 in fig. 4A, 5A, and 6A.

As shown in fig. 8A, the temperature sensing circuit 800 may include a power supply 801, a first transistor device 802, a resistor 804, a second transistor device 806, and an electrical ground 808. The power supply 801 may provide power to the temperature sensing circuit 800. The first transistor device 802 may be a PMOS device electrically coupled to the power supply 801 through its source terminal. The first transistor device 802 may also be an NMOS device electrically coupled to the power source 801 through its drain terminal. The gate terminal of the first transistor device 802 may be controlled by a bias voltage such that the first transistor device 802 may provide a desired current through the resistor 804 and the second transistor device 806.

As shown. As shown in fig. 8A, the drain terminal or source terminal of the first transistor device 802 is electrically coupled to a terminal of a resistor 804, depending on whether the first transistor device 802 is a PMOS device or an NMOS device. The resistor 804 may generate a voltage drop from a first terminal electrically coupled to the resistor 804. The first transistor device 802 is electrically coupled to a second terminal that is electrically coupled to the second transistor device 806. Resistor 804 may also limit the current flowing through temperature sensing circuit 800. A second terminal of the resistor 804 is electrically coupled to a first terminal (e.g., a collector terminal) of the second transistor device 806.

A second transistor device 806, as shown in fig. 8. As shown in fig. 8A, a PNP bipolar transistor may be used. In some embodiments, the second and third (e.g., base and emitter) terminals of the second transistor device 806 may be electrically coupled together such that the second transistor device 806 may function as a forward biased PN junction diode device, which may be used as a temperature sensor. The second transistor device 806 (e.g., a forward biased PN junction diode device) may exhibit a linear relationship between forward bias voltage and temperature. The second transistor device 806 may have a negative temperature coefficient. Those skilled in the art will readily appreciate that the second transistor device 806 may also be an NPN bipolar transistor, a diode, or any other type of device that may exhibit a linear voltage-temperature relationship. By using the second transistor device 806, the temperature sensing circuit 800 can generate the temperature sensing voltage V803 having a linear relation with the temperature variation.

As shown in the figure. Fig. 8B is a graph 840 illustrating an exemplary relationship between temperature sensing signals (such as temperature sensing voltage V803) shown in fig. 8B. Fig. 8A and temperature variation. In some embodiments, the temperature sensing voltage V803 may be measured at a third (e.g., drain) terminal of the first transistor device 802. Referring to fig. 8B, a graph 840 shows that the temperature sensing voltage V803 may vary linearly or substantially linearly with temperature. Thus, the temperature sensing circuit 800 may be used to measure temperature changes in a linear manner.

As shown in the figure. Fig. 9 is a flow chart representing an exemplary method for controlling the frequency of an oscillator. It will be readily appreciated that the illustrated process may be altered to delete steps or further comprise additional steps. After start-up, the system (e.g., system 200) generates two or more temperature sensing signals (step S920), such as temperature sensing voltages, via two or more temperature sensing circuits (e.g., temperature sensing circuits 202 and 204). The temperature sensing voltage may vary in response to changes in temperature obtained by two or more temperature sensing circuits. As a result, the temperature-sensing voltage may represent or substantially represent a change in temperature. In some embodiments, the temperature sensing signal may be generated by using a temperature sensor (e.g., a forward biased PN junction diode device) that exhibits a linear relationship between forward bias voltage and temperature.

As shown in fig. 9, step S930 system generates a reference signal that is constant or substantially constant with respect to changes in environmental conditions (e.g., changes in temperature) via a reference signal generation circuit (e.g., reference signal generation circuit 206). As an example, the reference signal may be generated by a reference signal generating circuit (e.g., a bandgap voltage reference generating circuit) capable of providing a substantially constant reference voltage over a desired range of temperature variations. Furthermore, the reference signal may have any desired value.

In step S940, after generating the temperature sensing signal and the reference signal, the system provides two or more curve generating signals, such as a current sensing signal and a reference signal, based on the temperature via a curve function generating circuit (e.g., curve function generating circuit 208). As described above, with the differential circuit, two or more curve generating currents may be provided by comparing the reference signal and the corresponding temperature sensing signal. The two or more curve generating currents may also have different current levels and different curves to provide coarse and fine tuning of the sum of the curve generating currents and to provide a better match to the oscillator frequency curve.

In step S950, after providing the two or more curve generating signals, the system generates a first signal (e.g., total current I317) for controlling the frequency of the oscillator based on the two or more curve generating signals via a summing circuit (e.g., summing circuit 340). The first signal may have a curve including one or more third or higher order components. And the curve of the first signal corresponds to the current level and two or more curves generating a curve of the current.

After generating the first signal, the method 900 may also proceed to a further step (not shown) comprising providing a second signal (e.g., signal S2 708), which may have a temperature change; a control voltage for controlling the frequency of the oscillator is generated based on the first current and the second current. It will be appreciated by those of ordinary skill in the art that the above-described flow steps may also be repeated as desired.

It will be apparent to those skilled in the art that the modules or steps of the invention described above may be implemented in a general purpose computing device, they may be concentrated on a single computing device, or distributed across a network of computing devices, or they may alternatively be implemented in program code executable by computing devices, such that they may be stored in a memory device for execution by the computing devices, or they may be separately fabricated into individual integrated circuit modules, or multiple modules or steps within them may be fabricated into a single integrated circuit module. Thus, the present invention is not limited to any specific combination of hardware and software.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (12)

1. A crystal oscillator, comprising:

An oscillator;

A system for controlling the frequency of the oscillator, wherein the system comprises:

A plurality of temperature sensing circuits, wherein each of the plurality of temperature sensing circuits is configured to generate a temperature sensing signal corresponding to a temperature acquired by the each temperature sensing circuit;

A reference signal generation circuit for generating a reference signal;

A first curve function generating circuit coupled to the two or more temperature sensing circuits and the reference signal generating circuit, the first curve function generating circuit for providing two or more curve generating signals based on the temperature sensing signals and the reference signal;

An adder circuit is coupled to the first curve function generating circuit for providing a first signal for controlling the frequency of the oscillator based on the two or more curve generating signals.

2. The crystal oscillator of claim 1, wherein the first curve function generation circuit comprises two or more differential circuits, each of the two or more differential circuits comprising a pair of transistor devices configured to receive the reference signal and a corresponding temperature sense signal.

3. The crystal oscillator of claim 2, wherein each of the two or more differential circuits is configured to compare the reference signal to a received respective temperature sense signal.

4. The crystal oscillator of claim 2, wherein the transistor device is a p-type metal oxide semiconductor PMOS device or an n-type metal oxide semiconductor NMOS device.

5. The crystal oscillator of claim 1, wherein the temperature sensing signal and the reference signal are voltage signals.

6. The crystal oscillator of claim 1, wherein the two or more curve generating signals are current signals having different signal levels and different curves.

7. The crystal oscillator of claim 6, wherein the first signal has a profile including one or more third or higher order components, the profile of the first signal corresponding to the signal level and the profile of the two or more profile-generating signals.

8. The crystal oscillator of claim 2, wherein the summing circuit includes one or more resistor devices coupled to the corresponding transistor device.

9. The crystal oscillator of claim 1, wherein at least one of the temperature sensing circuits comprises a bipolar device configured to acquire a temperature change and generate a temperature sensing voltage based on the acquired temperature change.

10. The circuit of claim 1, wherein the reference signal generation circuit comprises a bandgap voltage reference generation circuit configured to provide a reference voltage that is substantially constant with respect to temperature variations.

11. The crystal oscillator of claim 1, further comprising: a second curve function generating circuit configured to provide a second signal having a linear relationship with respect to temperature changes; an adder configured to generate a control signal for controlling a frequency of the oscillator based on the first signal and the second signal.

12. The crystal oscillator of claim 11, wherein the crystal oscillator comprises: a voltage controlled oscillator.