Temperature compensated oscillator driver

Abstract

A temperature-compensated oscillator driver. A circuit (100) includes an oscillator (110) having a driver (130) and a resonator (132). The driver (130) receives a supply voltage at a supply input (140) and provides a drive output (150) to drive the resonator (132) to generate an oscillator output signal (114). A power converter (170) receives an input voltage and generates the supply voltage to the supply input (140) of the driver (130). A temperature tracking device (180) in the power converter (170) controls a voltage level of the supply voltage to the supply input (140) of the driver (130) based on temperature such that the supply voltage inversely varies with the temperature of the circuit (100).

Description

[0001] Information related to divisional application

[0002] This is a divisional application. The parent application of this divisional application is Chinese invention patent application entitled "Temperature Compensated Oscillator Driver", filed on March 10, 2017, with application number 201710140196.8. Technical Field

[0003] This invention relates to integrated circuits, and more particularly, to a temperature-compensated oscillator driver. Background Technology

[0004] Wireless sensor networks (WSNs) (sometimes referred to as wireless sensor and actuator networks (WSANs)) are spatially distributed autonomous sensors or nodes that monitor / control physical or environmental conditions (e.g., temperature, sound, pressure, etc.). Sensors or actuators on the network cooperate to transmit collected data through the network to a central location where the data is analyzed, stored, and / or commands are sent to operate the respective network nodes. Many networks are bidirectional, thus enabling control of sensor activity. These networks and nodes are used in many industrial and consumer applications (e.g., industrial process monitoring and control, machine health monitoring, etc.). A key factor in operating nodes on the network is very low power consumption.

[0005] Power consumption is a significant factor in such networks because the devices used at each node are relatively inexpensive and typically operate on battery power. One way to reduce the power consumption of low-power wireless networks is to incorporate intermittent data transmissions (burst operations) when sending and receiving data to and from nodes. Sometimes a sleep timer is used to synchronize these burst operations. Because the sleep timer is usually always on, it needs to be very low-power and highly accurate to achieve the lowest possible system power. However, the conventional crystal oscillator driver in the sleep timer exhibits significant temperature variations, resulting in higher power consumption at high temperatures and consequently reduced battery life. Summary of the Invention

[0006] This invention relates to a temperature-compensated oscillator driver. In one example, the circuit includes an oscillator having a driver and a resonator. The driver receives a supply voltage at a supply input and provides a drive output to drive the resonator to generate an oscillator output signal. A power converter receives an input voltage and generates the supply voltage to the supply input of the driver. A temperature tracking device in the power converter controls the voltage level of the supply voltage to the supply input of the driver based on temperature, such that the supply voltage varies inversely to the temperature of the circuit.

[0007] In another example, a circuit includes an oscillator having a driver and a crystal resonator. The driver receives a supply voltage at a supply input and provides a drive output to drive the crystal resonator to generate an oscillator output signal. A linear regulator receives an input voltage and generates the supply voltage to the supply input of the driver. The linear regulator includes: a pass transistor that provides the supply voltage to the supply input of the driver; and a leakage current generating device that supplies current to operate the gate of the pass transistor. A temperature tracking device is operatively coupled to the leakage current generating device and the gate of the pass transistor in the linear regulator. The temperature tracking device controls the voltage level of the supply voltage to the supply input of the driver based on temperature via the pass transistor, such that the supply voltage varies inversely with the temperature of the circuit.

[0008] In another example, a device includes a remote sensor device comprising radio circuitry that communicates with the device via a wireless network connection. The remote sensor device includes timing circuitry that operates the device. The timing circuitry includes an oscillator having a driver and a crystal resonator. The driver receives a supply voltage at a supply input and provides a drive output to drive the crystal resonator to generate an oscillator output signal. A power converter in the timing circuitry receives an input voltage and generates the supply voltage to the supply input of the driver. A temperature tracking device in the power converter controls the voltage level of the supply voltage to the supply input of the driver based on temperature, such that the supply voltage input varies inversely with the temperature of the timing circuitry. Attached Figure Description

[0009] Figure 1 This section illustrates a block diagram of an example circuit that provides temperature compensation for an oscillator driver.

[0010] Figure 2 This section illustrates a schematic block diagram of an example circuit that provides temperature compensation for a crystal oscillator driver.

[0011] Figure 3 This describes the power characteristics of an example power converter that provides temperature compensation for a crystal oscillator driver.

[0012] Figure 4 This diagram illustrates a configurable power converter circuit that provides temperature compensation for a crystal oscillator driver.

[0013] Figure 5 A table of examples illustrating the operating range of circuits that provide temperature compensation for crystal oscillator drivers.

[0014] Figure 6 This section illustrates the operating power curve of an example circuit that provides temperature compensation for a crystal oscillator driver.

[0015] Figure 7 This diagram illustrates an example device that provides temperature compensation for an oscillator driver in a remote sensor apparatus. Detailed Implementation

[0016] This invention relates to a temperature-compensated oscillator driver. As the temperature at the location of the oscillator (e.g., a crystal oscillator) increases, the corresponding driver circuit operating in the corresponding oscillator circuit may experience a sharp increase in current. Under such dynamic temperature conditions, in a conventional circuit, the battery supply voltage to the driver may decrease with increasing current load. The temperature-compensated driver described herein includes a power converter that supplies voltage to the driver, the power converter decreasing the supply voltage supplied to the driver as temperature increases to mitigate the increase in power in the driver.

[0017] In one example, the circuit includes an oscillator with a driver and a resonator. The driver receives a supply voltage at a supply input and provides a drive output to drive the resonator to generate an oscillator output signal. The power converter, in turn, receives an input voltage and generates a supply voltage to the supply input of the driver. A temperature tracking device in the power converter controls the voltage level of the supply voltage to the supply input of the driver based on temperature. The voltage to the driver is controlled such that the supply voltage changes inversely with the circuit temperature (e.g., as the temperature increases, the supply voltage decreases, and vice versa). In this way, the driver power decreases as the temperature increases, thereby preserving the battery life of the circuit utilizing the oscillator and driver. Various devices in the power converter can be selectively switched to adjust the operating range of the converter (e.g., operating within a voltage and / or current range with temperature). Generally, any power converter that utilizes a temperature tracking device to reduce the supply voltage based on the temperature of the circuit as described herein can be used. These converters may include, for example, linear regulators, switched capacitor supplies, and inductor-based switching supplies.

[0018] Figure 1This describes an example circuit 100 that provides temperature compensation for an oscillator driver. As used herein, the term "circuit" may include a collection of active and / or passive components that perform circuit functions (e.g., analog, digital, or control circuitry). The term "circuit" may also include, for example, an integrated circuit whose entire circuitry is fabricated on a common substrate. Circuit 100 includes an oscillator 110 having a driver 130 and a resonator 132 (e.g., a crystal resonator). The driver receives a supply voltage at a supply input 140 and provides a drive output 150 to drive the resonator 132 to generate an oscillator output signal 114 at output 120. As shown, the drive output 150 drives a signal 154 to the resonator 132, wherein the signal 154 is out of phase with the oscillator signal 114. The signal 114 is fed back to input 160 of the driver 130, wherein the driver operates as an inverter. A power converter 170 receives the input voltage and generates a supply voltage to the supply input 140 of the driver 130. The temperature tracking device 180 in the power converter 170 controls the voltage level of the supply voltage to the supply input 140 of the driver 130 based on temperature, causing the supply voltage to change inversely to the temperature of the circuit 100. Therefore, as the temperature of the circuit 100 increases, the temperature tracking device 180 in the power converter 170 causes the supply voltage to dynamically decrease at the supply input 140 of the driver 130. In this way, the power in the circuit 100 can be reduced because the driver 130 consumes less power at the lower supply voltage at input 140.

[0019] In this example, resonator 132 may be a crystal resonator, a microelectromechanical system (MEMS) resonator, or an LC network resonator; however, generally, any type of resonator circuit may be used.

[0020] The power converter 170 can generally be any type of regulated power supply that attempts to regulate a constant output supply voltage based on a given input voltage. However, as temperature changes, the temperature tracking device 180 causes a change in the supply voltage to the supply input 140 of the driver 130 to compensate for current changes within the driver due to temperature variations. In one example, the power converter 170 can be a switched capacitor power supply, or it can be an inductor-based switched power supply that receives an input voltage and generates a supply voltage to the supply input 140 of the driver 130. In another example, the power converter 170 can be a linear regulator (e.g., a low-dropout regulator (LDO)) that receives an input voltage and generates a supply voltage to the supply input 140 of the driver 130.

[0021] If a linear regulator is used as power converter 170, then the linear regulator may include a pass transistor device that provides the supply voltage to the supply input 140 of driver 130 (see example). Figure 4 The linear regulator may also include a leakage current generating device that supplies current to operate the gate of the pass transistor device. In this configuration, the gate leakage of the leakage current generating device supplies current to the temperature tracking device 180 to operate the gate of the pass transistor device. By controlling the current within the linear regulator through gate leakage, the power in the regulator can be further conserved.

[0022] The temperature tracking device 180 may be, for example, a diode, a field-effect transistor junction, or a bipolar transistor junction, and the temperature tracking device 180 changes its voltage inversely proportional to the temperature applied to the tracking device. This temperature-dependent variable voltage is applied to the gate of the pass transistor device in the linear regulator to control the supply voltage at the supply input 140 of the driver 130. A programmable switching device may be provided (see, for example...). Figure 4 The switching device can be configured to adjust the current or voltage operating range of the power converter 170 by means of several series-connected transistor devices, several series-connected leakage current generating devices, or several series or parallel temperature tracking devices in a linear regulator.

[0023] Figure 2 This describes an example circuit 200 that provides temperature compensation for a crystal oscillator driver 210. The crystal oscillator driver 210 (also referred to as a driver) is an inverter, and it drives its resistive output to one lead of a crystal resonator 220 via a resistor R1. The other lead of the crystal resonator 220 is coupled to the input of the driver 210. A resistor R2 can also be used to improve the oscillator stability in circuit 200. An input voltage, shown as VDD, drives a power converter 230, which provides a supply voltage LVDD (e.g., local VDD) to operate the driver 210. In one example, VDD may be greater than 1 volt (e.g., 1.2 volts) and LVDD may be less than 1 volt (e.g., 0.5 volts). As the temperature of the entire circuit 200 changes, a temperature tracking device (TTD) 240 causes the voltage LVDD to change based on the temperature to mitigate power losses in the driver 210 as described herein. The power converter 230 has a voltage that is supplied and adjusted according to temperature changes. Figure 3 Some operating characteristics are illustrated in the voltage diagram depicted in the figure.

[0024] Figure 3This section illustrates the power characteristics of an example power converter that provides temperature compensation for a crystal oscillator driver as described herein. One characteristic of the power converter described herein is that it maintains a substantially constant output voltage (LVDD) for a given input voltage (VDD) at any given temperature. This relationship is shown at 310, where LVDD is illustrated on the vertical axis and VDD on the horizontal axis. As shown, LVDD is maintained at a substantially constant voltage as VDD increases. At 320, the characteristic of LVDD changing with temperature is plotted along the vertical axis. As shown at 320, the temperature tracking device described herein causes LVDD to decrease (e.g., decrease in a substantially linear manner) as temperature increases.

[0025] Figure 4 This describes a configurable power converter circuit 400 that provides temperature compensation for a crystal oscillator driver. In this circuit example, for illustrative purposes, the crystal resonator and driver forming the oscillator described herein are represented as load current 410. A linear regulator 420, operating as the power converter described herein, receives an input voltage VDD and generates a supply voltage LVDD to the supply input of the driver (see example). Figure 1 and 2 The linear regulator 420 includes a pass transistor device 430 that provides a supply voltage LVDD to the supply input of a driver, represented as a current source 410. A capacitor C1 (or multiple capacitors) may also be presented to filter LVDD. A leakage current generating device 440 supplies current to a diode D1 to operate the gate of the pass transistor device 430. In this example, the diode D1 operates as a temperature tracking device as described herein and is operatively coupled to the leakage current generating device 440 and the gate of the pass transistor 430 in the linear regulator 420. The temperature tracking device D1 controls the voltage level of the supply voltage LVDD to the supply input of the driver based on temperature via the pass transistor device 430, such that the supply voltage LVDD varies inversely with temperature. As the temperature of D1 increases, its voltage drop decreases, and this decrease is caused by gate control via the pass transistor device 430.

[0026] To maintain the minimum power level in the linear regulator 420, the gate leakage of the leakage current generating device 440 supplies current to the temperature tracking device D1 to operate the gate of the pass transistor device 430. As previously described, for example, in this example, the temperature tracking device D1 may be a diode. Other examples include a field-effect transistor junction or a bipolar transistor junction, which changes its voltage inversely proportional to the temperature applied to the tracking device. This temperature-dependent variable voltage is applied to the gate of the pass transistor device 430 to control the supply voltage LVDD.

[0027] A programmable switching device 450 can be used to adjust the current or voltage operating range of the linear regulator. For example, the switching device 450 can be programmed via factory setting commands, field user commands, and / or remote network control commands. The switching device 450 may include a user-programmable switch that enables or disables one or more series and / or parallel devices in the linear regulator 420 to control the operating range of the regulator. Disabling may include closing a switch that shorts the series device, while enabling may include opening a switch to effectively insert the series device into the circuit. For example, the switching device 450 can configure several series-pass transistor devices 430 or several series leakage current generating devices 440 by enabling or disabling control switches across the respective series devices. Programming may also include switching several series or parallel temperature tracking devices to adjust the current or voltage operating range of the linear regulator 420.

[0028] Figure 5 Table 500 illustrates the operating range of a circuit that provides temperature compensation for a crystal oscillator driver. As shown, for a given value of VDD and a temperature range of -40°C to approximately 90°C, the current in the driver is maintained at a relatively constant value of approximately 11 nanoamps (nA), and the power is maintained at approximately 10.5 nanowatts (nW). If VDD increases to 1.2 volts, the current in the converter is maintained at approximately 11 nA, but the power increases to approximately 13 nW, due to power conversion losses in the linear regulator at higher VDD values.

[0029] Figure 6 This section illustrates an example of an operating power curve for a circuit that provides temperature compensation for a crystal oscillator driver. In this example, conventional power curves 610 and 620 are shown, where power is plotted on the vertical axis relative to temperature on the horizontal axis. Each of the conventional curves 610 and 620 illustrates that the power in the driver increases as temperature increases. When using a temperature tracking device as described herein, a power curve 630 can be provided that shows the power in the driver circuit remains substantially constant over time as temperature increases, attributed to temperature-based changes in the driver's supply voltage as described herein.

[0030] Figure 7This describes an example device that provides temperature compensation for an oscillator driver in a remote sensor device 700. The remote sensor device 700 (e.g., a sensor, data collector, or controllable output device) includes radio circuitry 710 that communicates with the device via a wireless network connection. The remote sensor device 700 includes timing circuitry 720 that operates the device. Timing circuitry 720 includes an oscillator having a driver 730 and a crystal resonator 740. Driver 730 receives a supply voltage at supply input 750 and provides a drive output 754 to drive crystal resonator 740 to generate an oscillator output signal at output 756. A power converter 760 in timing circuitry 720 receives an input voltage and generates a supply voltage to supply input 750 of driver 730. A temperature tracking device 770 in power converter 760 controls the voltage level of the supply voltage to supply input 750 of driver 730 based on temperature, such that the supply voltage input varies inversely with the temperature of timing circuitry 720.

[0031] As previously described, the power converter 760 may be a linear regulator that receives an input voltage and generates a supply voltage to the supply input 750 of the driver 730. The linear regulator may include: a pass transistor device that provides the supply voltage to the supply input 750 of the driver 730; and a leakage current generating device that supplies current to operate the gate of the pass transistor device. The gate leakage of the leakage current generating device may be used to supply current to a temperature tracking device 770 to operate the gate of the pass transistor device. The temperature tracking device 770 may be a diode, a field-effect transistor junction, or a bipolar transistor junction, and the temperature tracking device 770 changes its voltage inversely proportional to the temperature applied to the tracking device, and the voltage is applied to the gate of the pass transistor device to control the supply voltage. A programmable switching device may be provided (see, for example). Figure 4 This allows for adjustment of the current or voltage operating range of the power converter 760.

[0032] Examples have been described above. It is impossible to describe every possible combination of components or methods, but those skilled in the art will recognize that many other combinations and arrangements are possible. Therefore, this invention is intended to include all such modifications, alterations, and variations falling within the scope of this application, which includes the appended claims. As used herein, the term "includes" means to include but is not limited to, and the term "including" means to include but is not limited to. The term "based on" means at least partially based on. Furthermore, when the invention or claims refer to an element "a," "first," or "another," or its equivalent, it should be interpreted as including one or more of such elements, neither requiring nor excluding two or more such elements.

Claims

1. A circuit comprising: Power converter, comprising: Input, which is configured to receive input voltage; Output; A first transistor includes a source coupled to the input, a drain coupled to the input, and a gate; A transfer transistor device coupled between the input and the output, the transfer transistor device including a gate coupled to the gate of the first transistor; and A temperature tracking device coupled to the gate of the first transistor and the gate of the transfer transistor device, the power converter being configured to generate a supply voltage at the output based on the input voltage and the temperature of the circuit; A programmable switching device coupled to the power converter, the programmable switching device being configured to adjust the range of current or voltage for the power converter; and An oscillator having an input coupled to the output of the power converter.

2. The circuit according to claim 1, wherein the oscillator comprises: The driver includes: Input, which is coupled to the output of the power converter; and The driver is configured to generate a drive output based on the supply voltage; and A resonator, comprising: The input, which is coupled to the output of the driver; and The resonator is configured to generate an oscillator output signal at the output based on the drive output.

3. The circuit according to claim 2, wherein the resonator is a crystal resonator, a microelectromechanical system (MEMS) resonator, or an LC network resonator.

4. The circuit of claim 2, wherein the power converter is a switched capacitor power supply or an inductor-based switched power supply that receives the input voltage and generates the supply voltage to the input of the driver.

5. The circuit of claim 2, wherein the power converter is a linear regulator that receives the input voltage and generates the supply voltage to the input of the driver.

6. The circuit of claim 1, wherein the gate leakage of the first transistor supplies current to the temperature tracking device to operate the gate of the transfer transistor device.

7. The circuit of claim 6, wherein the temperature tracking device is a diode, a field-effect transistor junction, or a bipolar transistor junction, the temperature tracking device changing its voltage inversely proportional to the temperature applied to the temperature tracking device, and the voltage being applied to the gate of the transfer transistor to control the supply voltage.

8. The circuit of claim 5, wherein the programmable switching device is configured to adjust the range of current or voltage operation of the power converter by means of a plurality of series-connected transfer transistor devices including the transfer transistor device, a plurality of series-connected leakage current generating devices including the first transistor, or a plurality of series-connected or parallel-connected temperature tracking devices including the temperature tracking device.

9. The circuit of claim 1, wherein the temperature tracking device comprises a first terminal coupled to the gate of the first transistor and the gate of the transfer transistor device, and a second terminal coupled to a ground node.

10. The circuit of claim 1, wherein the power converter further comprises a capacitor coupled between the output and the ground node.

11. The circuit of claim 1, wherein the first transistor comprises a body coupled to the input.

12. A linear regulator, comprising: Output; The first transistor includes a source, a drain coupled to the source, and a gate coupled to a node. A second transistor is coupled between the output and the source and drain of the first transistor, and the second transistor includes a gate coupled to the node; as well as A temperature tracking device coupled to the node.

13. The linear regulator of claim 12, wherein the temperature tracking device is a diode, a field-effect transistor junction, or a bipolar transistor junction.

14. The linear regulator of claim 12, wherein the second transistor is configured to generate a supply voltage at the output of the linear regulator.

15. The linear regulator of claim 14, wherein the supply current varies inversely with temperature.

16. The linear regulator of claim 12, wherein the source and drain of the first transistor are coupled to a voltage source, and the second transistor is coupled to the voltage source.

17. A linear regulator, comprising: Temperature tracking device; A leakage current generating device coupled to the temperature tracking device, the leakage current generating device being configured to receive an input voltage at the input of the linear regulator; and A transfer transistor device coupled to the temperature tracking device and the leakage current generating device, the transfer transistor device being configured to generate a voltage level of the supply voltage at the output of the linear regulator based on the input voltage and conversely based on the temperature of the linear regulator.

18. The linear regulator of claim 17, wherein the leakage current generating device is configured to supply current to operate the gate of the transfer transistor device.

19. The linear regulator of claim 18, wherein the gate leakage of the leakage current generating device supplies current to the temperature tracking device to operate the gate of the transfer transistor device.

20. The linear regulator of claim 19, wherein the temperature tracking device is a diode, a field-effect transistor junction, or a bipolar transistor junction, the temperature tracking device changing its voltage inversely proportional to the temperature applied to the temperature tracking device, and the voltage being applied to the gate of the transfer transistor to control the supply voltage.

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