MODIFIABLE OSCILLATOR CIRCUIT FOR OPERATING MODES

Abstract

Device comprising an oscillator circuit that is modifiable between a first operating mode and a second operating mode, wherein the first operating mode has a first frequency accuracy and a first power consumption, wherein the second operating mode has a second frequency accuracy and a second power consumption, the second frequency accuracy being more accurate than the first frequency accuracy and the second power consumption being higher than the first power consumption, and comprising a control circuit that communicates with the oscillator circuit to modify the operating mode of the oscillator circuit.

Description

RELATED PATENT APPLICATION

[0001] This application claims priority to commonly owned U.S. Patent Application No. 63 / 344,204 filed May 20, 2022, the entire contents of which are hereby incorporated by reference for all purposes. TECHNICAL FIELD

[0002] The present disclosure relates to modifiable oscillator circuits for operating modes having different clock frequency accuracies and power consumption states. BACKGROUND

[0003] Bluetooth is a specification published by Bluetooth SIG, Inc. in Kirkland, Washington, and uses a low-power radio. The specification defines a set of operating modes that include a peripheral device in an advertising state, a peripheral device in a connection state, and a central device in a connection state. The frequency of low-power RC (resistor-capacitor oscillators) may be inaccurate for Bluetooth connection scheduling—i.e., connection-state operation for both peripheral and central devices—but may be sufficient for meeting the relaxed design constraints on advertising event timing—i.e., peripheral device operation in the advertising state.For example, hearing aid applications require the use of accurate RC oscillators for the central device of + / -500 ppm for scheduling Bluetooth connections, but medical implant applications may use less accurate RC oscillators (greater than 500 ppm) for timing advertising events. For applications requiring accurate RC oscillators, the limiting factor of the design may be the impact of random telegraph noise (RTN). The magnitude of RTN in transistors can be reduced by increasing the transistor area, increasing the gate bias to shift the operable range away from the deep weak inversion, or by a combination of these.

[0004] For many low-power RC oscillators, the limiting factor for frequency accuracy can be the effect of RTN on the MOSFET transistors, rather than the effect of white noise or flicker noise. Unfortunately, increasing the transistor area alone cannot sufficiently reduce the RTN size, and increasing the transistor gate bias leads to an increase in the oscillator's power consumption.

[0005] There is a need for a way to reduce the power consumption in low-power RC oscillators used to operate Bluetooth Low Energy radios such as hearing aids and medical implants, while meeting the frequency accuracy requirements of peripheral and central interconnect and advertising use cases. SUMMARY OF THE INVENTION

[0006] The effects of RTN on low-power RC oscillators used for Bluetooth Low Energy radio operations can be mitigated by modifying the transistor operating range between weak, medium, and strong inversion using a programmable circuit to maintain a given frequency accuracy.

[0007] According to one aspect, an apparatus is provided comprising: an RC oscillator circuit modifiable between a first operating mode and a second operating mode, wherein the first operating mode has a first frequency accuracy and a first power consumption, wherein the second operating mode has a second frequency accuracy and a second power consumption, wherein the second frequency accuracy is more accurate than the first frequency accuracy and the second power consumption is higher than the first power consumption; and a control circuit communicating with the oscillator circuit to modify the operating mode of the oscillator circuit.

[0008] Another aspect features a method comprising: generating a first clock signal with an oscillator circuit in a first operating mode; transmitting a message using the first clock signal; modifying the oscillator circuit from the first operating mode to a second operating mode; generating a second clock signal with the oscillator circuit in the second operating mode; and transmitting a message using the second clock signal.

[0009] According to another aspect, a system is provided comprising: a power management circuit; a radio circuit electrically connected to the power management circuit, the radio circuit outputting signals to an antenna; an oscillator circuit electrically connected to the power management circuit, the oscillator circuit being modifiable between a first and a second operating mode, the first operating mode having a first frequency accuracy and a first power consumption, the second operating mode having a second frequency accuracy and a second power consumption, the second frequency accuracy being more accurate than the first frequency accuracy and the second power consumption being higher than the first power consumption;a control circuit electrically connected to the radio circuit, the power management circuit, and the oscillator circuit, the control circuit modifying the operating mode of the oscillator circuit; and a wake-up circuit electrically connected to the oscillator circuit and the power management circuit, the wake-up circuit generating a signal to the power management circuit based at least in part on the operating mode of the oscillator circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The figures illustrate exemplary oscillator circuits and systems for use in low-power wireless applications, such as Bluetooth applications. Fig. Figure 1A illustrates a diagram of a reduced-power RC oscillator circuit for a low-power radio application that includes three RC oscillators biased to one of three different levels. Fig. Figure 1B illustrates a diagram of a reduced-power RC oscillator circuit for a low-power radio application that includes two RC oscillators biased at one of two different levels. Fig. Figure 1C illustrates a diagram of a reduced-power RC oscillator for a low-power radio application that includes an RC oscillator that can be biased to three different states. Fig. Figure 1D illustrates a diagram of a reduced-power RC oscillator circuit for a low-power radio application that includes an RC oscillator that can be biased to two different states. Fig. Figure 2 illustrates timing diagrams for the transmission of a connection interval by a central device and a reception window of a peripheral device, as well as a deep sleep state. Fig. Figure 3A illustrates diagrams of three RC oscillators, each operating at different power consumption. Fig. Figure 3B illustrates diagrams of two RC oscillators, each operating with different power consumption. Fig. Figure 3C illustrates a diagram of a variable RC oscillator operable in three different power consumption states or modes. Fig. 3D illustrates a diagram of a variable RC oscillator operable in two different power consumption states or modes. Fig. Figure 3E illustrates a diagram of three RC oscillators, where two of the oscillators operate at different power consumption and the third oscillator is a variable RC oscillator operable in two different states or modes of power consumption. Fig. Figure 4 illustrates an example of RTN in MOSFET devices causing frequency deviations in an RC oscillator. Fig. Figure 5 illustrates one of several examples of RTN in a silicon channel interface. Fig. Figure 6 illustrates one of several examples of the influence of RTN on the threshold voltage of a MOSFET device. Fig. Figure 7 illustrates one of several examples of an RTN model. Fig. Figure 8 illustrates a device with an RC oscillator circuit and a control circuit. Fig. 9A illustrates a method for mitigating RTN by placing a device in an advertising state, operating an RC oscillator at a first power, placing the device in a connection state, and operating the RC oscillator at a second power. Fig. 9B illustrates a method as in Fig. 9A to place the device in a central state in a connection state and to operate the RC oscillator with a third power. Fig. Figure 10 illustrates a timing diagram for advertising events based on an advertising interval and a randomly generated advertising delay. Fig. 11 illustrates a method for mitigating RTN by generating a first clock signal, transmitting a message using the first clock signal, modifying the oscillator circuit, generating a second clock signal, and transmitting a message using the second clock signal. Fig. Figure 12A illustrates a bias generation circuit including a transistor with a fixed transistor area of ​​WxL consuming a bias current of IBIAS, where the operating region of the transistor is in weak inversion. Fig. 12B illustrates a bias generation circuit having a transistor with a fixed area WxL and a bias current IBIAS or 2xIBIAS switched via a switch SW, where the circuit may be controllable to modify a transistor operating range of the transistor in the oscillator circuit. Fig. 12C illustrates a bias generation circuit having two transistors with a fixed bias current IBIAS and a switched range of WxL or 2xWxL via a switch SW, where the circuit may be controllable to modify a transistor operating range of the transistors in the oscillator circuit. Fig. 12D illustrates a bias generation circuit having two transistors with fixed bias current IBIAS and a switched area of ​​WxL or Wx2xL via a switch SW, where the circuit may be controllable to modify a transistor operating area of ​​transistors in the oscillator circuit.

[0011] The reference numerals for each illustrated element that appears in several different figures have the same meaning in all figures, and mention or discussion of an illustrated element in connection with a particular figure also applies to any other figure in which the same illustrated element is shown, if any. DESCRIPTION

[0012] The power consumption of low-power RC oscillators used for radio transmissions such as Bluetooth Low Energy can be reduced by modifying the transistor's operating range, or the region between weak and strong inversion, using a programmable bias voltage to maintain a specific frequency accuracy.

[0013] Instead of using a fixed RC oscillator with a frequency accuracy of + / - 500 parts per million (ppm) or other desired frequency accuracy that consumes a specific power to maintain the desired frequency accuracy in the face of noise, including Random Telegraph Noise (RTN), either (1) a variety of discrete RC oscillators tailored to the power consumption versus frequency accuracy trade-off to meet the specific application case, or (2) one RC oscillator that has two or three bias current / capacitance settings to control the power consumption versus frequency accuracy trade-off for each specific application case.

[0014] A low-power RC oscillator can be used when implementing a low-power mode, such as advertising mode according to the Bluetooth specification mentioned above. A separate RC oscillator, internally biased with a higher current and / or larger transistors to reduce the RTN size, can be used in some applications where a higher average power consumption can be tolerated. This separate RC oscillator can be used when the operating mode requires precise clocking. This allows power consumption to be reduced when frequency accuracy tolerance is not an important criterion, and power consumption may increase when implementing a mode that requires a tighter frequency accuracy tolerance, especially if the frequency tolerance needs to be more precise.

[0015] Random Telegraph Noise (RTN), also known as Random Telegraph Signals (RTS), is caused by the trapping and release of channel charge carriers near the interface between the transistor gate oxide and the silicon channel. Fig. Figure 5 shows one of several examples of RTN in a silicon channel interface. When charge carriers are trapped, there is a sudden drop in the channel current, and when they are released, there is a sudden increase in the channel current. These sudden "telegraphic" events can occur with a frequency and magnitude that cannot be predicted and can lead to performance degradation in analog circuits. Low-power circuits can be sensitive to RTN because the magnitude of the channel current variation, i.e., ΔId / Id, increases as the transistor continues to be biased into the weak inversion (sub-threshold) region. This is unfavorable for low-power circuits that exploit an increase in transistor gain and low power consumption, since this exploitation requires the transistor to be biased relatively deeply into the weak inversion region. Fig. Figure 6 shows one of several examples of the effect of RTN on the threshold voltage (Vt) of a MOSFET device, showing an increase in Vt in response to a trapping event, this increase being sustained for a time after which the charge is emitted. Fig. Figure 6 similarly shows that this state is maintained for a period of time after which another capture event may occur.

[0016] The RTN phenomenon can be observed as ΔId in the transistor channel and can be modeled as ΔVt, which is telegraphic in nature. Fig. Figure 7 shows one of several examples of a model of RTN. The magnitude of ΔVt is proportional to ~1 / sqrt(area). The effect of RTN is greatest under weak inversion, where ΔId / Id increases due to a larger ratio of gm / Id, where gm represents the mutual conductance of the transistor during operation. The statistical distribution of ΔVt is modeled by an exponential distribution with a thick tail. RTN can become the dominant noise source in very low-power MOS circuit designs.

[0017] Bluetooth Low Energy, as specified by Bluetooth SIG, Inc., or Bluetooth LE, has two key states: the Advertising State and the Connection State. Implementations of a device that complies with the Bluetooth LE specification can use a low-power resistor-capacitor (RC oscillator) as the clock source with a timer to schedule Advertising and Connection events. At the end of an Advertising or Connection event, the timer can be set to a wake-up time, and the device can enter a low-power (deep sleep) state. Once the timer wakes the device from deep sleep, the device can advertise or establish a connection and return to deep sleep to conserve power before the next wake-up time. RTN affects the frequency accuracy of the oscillator and, therefore, the accuracy of the time at which the wake-up timer wakes the device from deep sleep.

[0018] The challenge for circuit design is to design an RC oscillator that consumes little power at a given voltage, e.g. a battery source, while maintaining the required frequency accuracy.

[0019] The telegraphic nature of RTN in transistors, which can provide sudden current jumps in the MOSFET transistors, can significantly affect the frequency accuracy of low-power RC oscillators. Fig. Figure 4 shows an example of how RTN noise affects the output frequency of a low-power RC oscillator. Large frequency excursions of -4000 ppm are observed for some of the devices. The average frequency accuracy for various devices with corresponding RC oscillators is 900 ppm. Reducing the RTN can be achieved by increasing the transistor operating area (to some extent) or by operating the oscillator at higher power. However, higher power is a problem for ultra-low-power designs for Bluetooth LE-based radios, such as medical implants.

[0020] In one example, three discrete RC oscillators or one RC oscillator with three bias settings may be used in a radio, e.g., a Bluetooth LE-based radio, to mitigate the effects of RTN for a peripheral device in an advertising state, a peripheral device in a connection state, and a central device in a connection state. In one example, a peripheral device may be a medical device implanted in a body, and a central device may be a smartphone. In another example, a peripheral device may be a first hearing aid and the central device may be a second hearing aid paired with the first hearing aid, and at certain times, the first and second hearing aids may swap roles so that the second hearing aid acts as the peripheral device and the first hearing aid acts as the central device.In another example, a hearing aid may be a peripheral device and a smartphone may be a central device.

[0021] The advertising state can be an asynchronous operating mode that does not require a high-precision clock source, for example, an asynchronous communication mode. It is often desirable to use very low power consumption in deep sleep for the advertising state. For example, a medical implant in the advertising state that advertises at five-second (5s) intervals might have an average power consumption of ~1.2µW, considering a 1.2V voltage source. An RC oscillator consuming 120nW in deep sleep would have a design constraint of 10% of the average power consumption.

[0022] The Connection State can be a synchronous operating mode, where a receive event (RX) of the peripheral device is synchronized with a central transmit event (TX), e.g., a synchronous communication mode. The timing accuracy of the central device must be within + / -500 ppm, but the timing accuracy of the peripheral device can be more relaxed, provided that sufficient RX window extension is used. Unfortunately, additional RX window extension results in additional power consumption. It is therefore important to balance the power required to reduce RTN in an RC oscillator to set a given frequency accuracy with the power consumption in the radio to support a given RX window extension.Another consideration for the peripheral in a connection state is that, due to the higher operating rate, it often consumes more power than the peripheral in an advertising state. For example, a hearing aid with a keep-a-live connection may have an average power consumption of ~12µW for connection events and ~60µW for 1 second and 100ms connection events, respectively, if the peripheral uses a 1.2V voltage source.

[0023] A first RC oscillator of the three discrete RC oscillators, or the single RC oscillator in a first of the three bias settings, has the respective transistors in weak inversion to increase transistor gain and reduce power consumption. Since advertising events are asynchronous in nature according to an asynchronous communication mode, the time between advertising events does not need to be precisely adjusted, and therefore a peripheral device in the advertising state can use the first RC oscillator or the single RC oscillator in the first bias setting. Increased RTN values ​​can cause increased frequency inaccuracy, which can be tolerated without causing problems in maintaining the relaxed timing requirements. An example of this is a medical implant that can be in deep sleep for 20 seconds or more between advertising events.Because advertising events are rare, the power of the RC oscillator can have a significant impact on battery life, accounting for more than 50% of the device's power consumption in the advertising state. Reducing the power consumption of the RC oscillator can extend the device's lifespan.

[0024] The second RC oscillator of the three discrete RC oscillators, or the RC oscillator in a second of the three bias settings, has the transistors in the weakly to moderately inverse region, i.e., it is biased with increased power consumption compared to the first RC oscillator or the single RC oscillator in the first bias setting, to reduce the effects of RTN on the oscillator period, i.e., on frequency accuracy. A peripheral device in the connection state can utilize the second RC oscillator of the single RC oscillator in the second bias setting. An example of this is a hearing aid device operating as a peripheral device and maintaining a 'keep alive' radio link with a link interval of 125 ms.Because the time interval between connection events is typically shorter than that between advertising events, the RC oscillator can consume higher power while still being significantly less than the total radio power consumption of the peripheral. The frequency accuracy of the RC oscillator for the peripheral can be designed to reduce, and in some cases minimize, the power consumption of the RC oscillator plus the radio with RX window extension.

[0025] The third RC oscillator of the three discrete RC oscillators or the RC oscillator in a third of the three bias settings has the transistors biased towards strong inversion, i.e. with increased power consumption compared to the second RC oscillator or the single RC oscillator in the second bias setting, in order to reduce the RTN to a level at which the oscillator can be used in a central device to provide the specified frequency accuracy, e.g. within + / -500ppm.

[0026] Fig. 1A shows the circuit 100 in various examples. A battery (VBATT) 102 provides power to a register circuit 104, a plurality of RC oscillators labeled (RC01) 106, (RC02) 108, and (RC03) 110, a clock multiplexer 112, a wakeup timer or circuit 114, and a power management circuit 116. In this example, the register 104 and the clock multiplexer 112 together form a circuit 122. The power management circuit 116 provides a VDD supply voltage to a microcontroller unit (MCU) 118 and a radio circuit 120. The radio circuit 120 may include an antenna 121 for transmitting a signal. Fig. The circuit 100 shown in Figure 1A may be implemented either in a peripheral device or in a central device. The circuit 100, or portions thereof, may be implemented by instructions in a storage medium for execution by a processor, a function, a library call, a subroutine, a shared library, software as a service, an analog circuit, a digital circuit, control logic, digital logic circuits programmed by a hardware description language, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device (PLD), or any suitable combination thereof, or any other suitable mechanism, whether in a single device or distributed across multiple devices.

[0027] In operation, the RC oscillator RCO1 106 can be activated when the circuit is used in a peripheral device in the advertising state, with a typical power consumption of more than 60 nW and less than 480 nW using a 1.2 V voltage source, but this is not to be construed as a limitation. The RC oscillator RCO2 108 can be activated when the circuit is used in a peripheral device in the connection state, with a power consumption greater than the power consumption of the RC oscillator RCO1 106, with a typical power consumption of more than 0.48 µW and less than 1.2 µW using a 1.2 V voltage source.The RC oscillator RCO3 110 can be activated when the circuit is used in a central device in the connection state, with a power consumption greater than the power consumption of the RC oscillator RCO2 108, with a typical power consumption of more than 1.2µW and less than 3µW when using a 1.2V voltage source. The clock multiplexer 112 can select the activated one of the RC oscillators RCO1 106, RCO2 108, or RCO3 110 for output to the wakeup timer or wakeup circuit 114. The wakeup timer or wakeup circuit 114 provides a signal to activate the power management circuit 116. The power management circuit 116 may provide the supply voltage VDD to the MCU 118 and the radio circuit 120, at least in part in response to the provided signal to activate the power management circuit 116.The firmware in the MCU 118 can detect whether the system is a central or peripheral device and whether the device is in an advertising or connection state and activate the corresponding RC oscillator by loading the register circuit 104 with the corresponding value. The register circuit 104 can respond at least in part to the loaded value and activate one of the RC oscillators RCO1 106, RCO2 108, and RCO3 110 via the respective enable inputs. The register circuit 104, which responds at least in part to the loaded value, can send a signal to the clock multiplexer 112 to forward the activated one of the RC oscillators RCO1 106, RCO2 108, and RCO3 110 to the wake-up timer or the wake-up circuit 114. In operation, when the RC oscillator RCO1 106 is enabled and passed from the clock multiplexer 112, the radio 120 as a peripheral in the advertising state provides signals according to the timing.The timing of the wake-up events does not necessarily have to have a predetermined frequency accuracy. When the RC oscillator RCO2 108 is enabled and passed, the radio 120 provides signals according to the timing as a peripheral device operating in the connection state. The timing of the wake-up events can be synchronized to occur during the connection interval, as shown in FIG. Fig. 2. When the RC oscillator RCO3 110 is activated and cycling, the radio 120 provides signals according to the timing as a central device operating in the connection state. The RC oscillator RCO3 110 can provide the frequency accuracy required by the respective specification. In one of the various examples, a timing accuracy tolerance of + / -500 ppm can be the required frequency accuracy for the central device operating in the connection state when operating in a Bluetooth Low Energy (BLE) system.

[0028] Fig. 1B shows the circuit 100, which has two RC oscillators RCO1 and RCO2. In operation, the RC oscillator RCO1 106 can be activated when the circuit is used in a peripheral device in the advertising state, with a typical power consumption of more than 60 nW and less than 480 nW using a 1.2 V voltage source, but this is not to be understood as a limitation. The RC oscillator RCO2 108 can be activated when the circuit is used in a peripheral or central device in the connection state, with a power consumption greater than the power consumption of the RC oscillator RCO1 106, with a typical power consumption of more than 1.2 µW and less than 3 µW using a 1.2 V voltage source.

[0029] Fig. Figure 1C shows circuit 200 in another example. A battery (VBATT) 202 provides power for a programmable RC oscillator 205, labeled RCO, a wakeup timer 214, and a power management circuit 216. The power management circuit 216 provides a VDD supply voltage to a microcontroller unit (MCU) 218 ​​and a radio circuit 220, which is at least partially responsive to a signal from the wakeup timer 214. The Fig. The circuit 200 shown in Figure 1C may be implemented either in a peripheral device or in a central device. The circuit 200 may be implemented, at least in part, by instructions in a storage medium for execution by a processor, a function, a library call, a subroutine, a shared library, software as a service, an analog circuit, a digital circuit, control logic, digital logic circuits programmed by a hardware description language, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device (PLD), or any combination thereof, or any other suitable mechanism, whether in a single device or distributed across multiple devices.The programmable RC oscillator RCO 205 can operate in a peripheral advertising state (State A), a peripheral connection state (State B), or a central connection state (State C). A signal from the MCU 218 can select either the peripheral advertising state (State A), the peripheral connection state (State B), or the central connection state (State C). The circuitry of the programmable RC oscillator RCO 205 can select a different bias state based on the MCU signal to maintain the frequency accuracy of the RC oscillator RCO for the correct State A, B, or C.

[0030] Fig. 1D shows the circuit 200 in another example that can be implemented in a peripheral device. The programmable RC oscillator RCO 205 can operate in a peripheral advertising state (State A) or in a peripheral or central connection state (State B). A signal from the MCU 218 can select either the peripheral advertising state (State A) or the peripheral or central connection state (State B). The programmable RC oscillator RCO 205 circuit can select a different bias state based on the MCU signal to maintain the frequency accuracy of the RC oscillator RCO for the correct State A or B.

[0031] Fig. Figure 2 shows a timing diagram of a connection interval for a central device in the Connection state, which transmits a signal at a predefined anchor point time, and a window for the detection of the preamble by a peripheral device in the Connection state. In a Bluetooth application, the central device can maintain a timing accuracy of + / -500 ppm per connection. The peripheral can enter a deep sleep mode between connection events. The peripheral can provide a window extension proportional to the TX timing accuracy (TX acc) + RX timing accuracy (RX acc). The power consumption of the radio peripheral is higher, the higher the timing accuracy TX acc + RX acc.

[0032] Fig. Figure 3A shows three types of RC oscillators. The RC oscillator RCO1 can be used by a peripheral device operating in an advertising state. The RC oscillator RCO1 can be used, for example, in a medical implant where low power consumption is an important design criterion. When using a 1.2V voltage source for the RC oscillator RCO1, the power consumption can be greater than 60nW and less than 480nW. Alternatively, the power consumption can be ~120nW when using a 1.2V voltage source for the RC oscillator RCO1 and the frequency accuracy is less than + / -500ppm, e.g., + / -4000ppm. The transistors in the RC oscillator RCO1 can be weakly inversion biased to improve transistor gain and reduce power consumption. Advertising can be an asynchronous event by nature and therefore does not require an exact time base, i.e., frequency accuracy.

[0033] The RC oscillator RCO2 can be used in a peripheral device that operates in a connection state. The RC oscillator RCO2 can be used, for example, in a hearing aid to maintain the connection while reducing power consumption. The power consumption could be greater than 480 nW and less than 1.2 µW if a 1.2 V voltage source is used for the RC oscillator RCO2. Alternatively, the power consumption could be ~600 nW if a 1.2 V voltage source is used for the RC oscillator RCO2. The transistors in the RC oscillator RCO2 can be biased in the weakly to moderately inverted region to reduce the effects of RTN and keep power consumption low. The peripheral device can have a clock frequency accuracy less than + / -500 ppm, such as + / -600 ppm. Alternatively, the clock frequency of the peripheral device can be more precise, e.g. + / -400ppm.The average power consumption of the link can be determined based on two variables: the power consumption of the RC oscillator to support a given frequency accuracy and the power consumption of the RX oscillator, which is affected by an additional window extension to compensate for the difference between the required frequency accuracy and the provided frequency accuracy.

[0034] The RC oscillator RCO3 can be used in a central device operating in the connection state. For example, the RC oscillator RCO3 can be used in a hearing aid that serves as the central device for maintaining the connection. The power consumption can be greater than 1.2 µW and less than 3 µW when using a 1.2 V voltage source for the RC oscillator RCO3. Alternatively, the power consumption can be ~2.4 µW when using a 1.2 V voltage source for the RC oscillator RCO3. The transistors in RCO3 can be biased in the moderately to strongly inverted region to reduce the effects of RTN. In a Bluetooth application, the RC oscillator RCO3 can meet a frequency accuracy tolerance of + / -500 ppm.

[0035] Fig. Figure 3B shows two types of RC oscillators. The RC oscillator RCO1 can be used by a peripheral device operating in an advertising state. When using a 1.2V voltage source for the RC oscillator RCO1, the power consumption can be greater than 60nW and less than 480nW. Alternatively, the power consumption can be ~120nW when using a 1.2V voltage source for the RC oscillator RCO1 with a frequency accuracy of less than + / -500ppm, such as + / -4000ppm. The transistors in the RC oscillator RCO1 can be weakly inversion biased to improve transistor gain and reduce power consumption. The RC oscillator RCO2 can be used in the peripheral or the central device operating in a connection state. The power consumption could be greater than 1.2µW and less than 3µW if a 1.2V voltage source is used for the RC oscillator RCO2.Alternatively, the power consumption could be ~2.4 µW if a 1.2 V voltage source is used for the RC oscillator RCO2. The peripheral or central device can have a clock frequency accuracy of + / -500 ppm.

[0036] Fig. Figure 3C shows a variable RC oscillator, RC oscillator RCO4, which can be used in a peripheral device operating in the advertising state, in a peripheral device operating in the connection state, and in a central device operating in the connection state. The mode_sel signal can select either the advertising state of the peripheral device (state A), the connection state of the peripheral device (state B), or the connection state of the central device (state C). The RC oscillator RC04 circuit can select a different bias condition based on the mode_sel setting to maintain the frequency accuracy of the RC oscillator RCO4 for the correct state A, B, or C. For example, state A can be selected to achieve a power consumption of more than 60 nW and less than 480 nW when using a 1.2 V voltage source for the RC oscillator RCO4.Alternatively, State A can specify a power consumption of ~120 nW using a 1.2 V voltage source for the RC oscillator RCO4. Selecting State B can specify a power consumption of more than 480 nW and less than 1.2 µW using a 1.2 V voltage source for the RC oscillator RCO4. Alternatively, State B can specify a power consumption of ~600 nW using a 1.2 V voltage source for the RC oscillator RCO4. Selecting State C can specify a power consumption of more than 1.2 µW and less than 3 µW using a 1.2 V voltage source for the RC oscillator RCO4. Alternatively, State C can specify a power consumption of -2.4 µW using a 1.2 V voltage source for the RC oscillator RCO.

[0037] Fig. Figure 3D shows a variable RC oscillator, the RC oscillator RCO4, which can be used in a peripheral device operating in the advertising state or the connection state. The mode_sel signal can select either the advertising state of the peripheral device (state A) or the connection state of the peripheral or central device (state B). The RC oscillator RCO4 circuit can select a different bias condition based on the mode_sel setting to maintain the frequency accuracy of the RC oscillator RCO4 for the correct state A or B. For example, state A can be selected such that the power consumption is greater than 60 nW and less than 480 nW when a 1.2 V voltage source is used for the RC oscillator RCO4. Alternatively, State A can set the power consumption to ~120nW using a 1.2V voltage source for the RC oscillator RCO4.The choice of State B can set the power consumption to more than 1.2µW and less than 3µW when using a 1.2V voltage source for the RC oscillator RCO4. Alternatively, State B can set a power consumption of ~2.4µW when using a 1.2V voltage source for the RC oscillator RCO4.

[0038] Fig. Figure 3E shows three types of RC oscillators. The RC oscillator RCO1 can be used by a peripheral device operating in an advertising state. The power consumption can be greater than 60 nW and less than 480 nW when a 1.2 V voltage source is used for the RC oscillator RCO1. Alternatively, the power consumption can be ~120 nW when a 1.2 V voltage source with a frequency accuracy of less than + / -500 ppm, such as + / -4000 ppm, is used for the RC oscillator RCO1. The transistors in the RC oscillator RCO1 can be weakly inversion biased to improve transistor gain and reduce power consumption. The RC oscillator RCO2 can be used in the peripheral or the central device operating in a connection state. The power consumption could be more than 1.2µW and less than 3µW if a 1.2V voltage source is used for the RC oscillator RCO2.Alternatively, the power consumption could be ~2.4 µW if a 1.2 V voltage source is used for the RC oscillator RCO2. The peripheral or central device can have a clock frequency accuracy of + / -500 ppm. RC oscillator RCO3, which can be used in a peripheral device operating in the advertising state or the connection state. The mode_sel signal can select either the advertising state of the peripheral device (state A) or the connection state of the peripheral or central device (state B). The RC oscillator RCO3 circuit can choose a different bias condition based on the mode_sel setting to maintain the frequency accuracy of the RC oscillator RCO3 for the correct state A or B. For example, state A can be chosen so that the power consumption is greater than 60nW and less than 480nW when a voltage source of 1.2V is used for the RC oscillator RCO3.Alternatively, State A can specify a power consumption of ~120 nW when using a 1.2 V voltage source for the RC oscillator RCO3. The choice of State B can set the power consumption to more than 1.2 µW and less than 3 µW when using a 1.2 V voltage source for the RC oscillator RCO3. Alternatively, State B can specify a power consumption of ~2.4 µW when using a 1.2 V voltage source for the RC oscillator RCO3.

[0039] Fig. 8 illustrates a device including an RC oscillator circuit 805 and a control circuit 822.

[0040] Fig. 9A illustrates a method for placing 902 a peripheral device in an advertising state, 904 operating an RC oscillator in a first bias state, 906 placing the device in a peripheral device in a connection state, and 908 operating the RC oscillator in a second bias state.

[0041] Fig. Figure 9B illustrates an alternative method that may include switching 910 the device to a central device in a connection state and operating 912 the RC oscillator in a third bias state. For the methods of Fig. 9A and Fig. 9B, the sequence is not required to occur in a particular order, and thus, a peripheral device in the Advertising State can transition to a central device in the Connection State, i.e., to operating the RC oscillator in the third bias state, without exceeding the scope. Similarly, the methods may include transitioning the device from the second bias state to the first bias state or transitioning the device from the third bias state to the first bias state.

[0042] In one example, the device may be selected from a low-power peripheral radio and a low-power central radio, and an operating state may be selected from a radio advertising state, a peripheral radio connection state, and a central radio connection state, with corresponding power consumption and frequency accuracy.

[0043] Fig. Figure 10 illustrates a timing diagram for advertising events. An advertising state can be initiated by a peripheral device. It can send data on predetermined channels, e.g., channels 37 / 38 / 39, to other devices that may be listening. The data can be an advertising message, and the transmission of the advertising message can be an advertising event. An advertising event can be an asynchronous event, so that between successive advertising events there can be an advertising period (T_advEvent) with a random time component (advDelay) according to an asynchronous communication mode, as shown. In this context, asynchronous means that the peripheral can initiate an advertising message at any time, and the advertising period is random from the perspective of the receiver (i.e., the central device).A central device can listen to the specified channels, allowing the advertising event to occur at any time. The peripheral device may have no knowledge of when the central device is listening. The advertising period can determine the time between consecutive transmissions of an advertising message. Therefore, the accuracy of the advertising period is not critical. Once a connection is established, the time between the central device and the peripheral device can be synchronized. Relaxed clock accuracy can be used to conserve power during the deep sleep interval in the peripheral device when it is in the advertising state.

[0044] Fig. 11 illustrates a method for generating 1102 a first clock signal with an oscillator circuit in a first operating mode, transmitting 1104 a message using the first clock signal, modifying 1106 the oscillator circuit from the first operating mode to a second operating mode, generating 1108 a second clock signal with the oscillator circuit in the second operating mode, and transmitting 1110 a message using the second clock signal.

[0045] Although the examples have been described above, other variations and examples may be derived from this disclosure without departing from the spirit and scope of these disclosed examples.

[0046] Fig. Figure 12A shows a bias generation circuit 300 including a transistor 301 with a fixed transistor area of ​​WxL that draws a bias current of IBIAS. The region in which the transistor operates is weakly inverted.

[0047] Fig. 12B shows a bias generation circuit 300 with a transistor 301 with a fixed area WxL and a switched bias current IBIAS or 2xIBIAS via a switch SW. The operable range of the transistor depends on the bias current and is in weak inversion at a bias current of IBIAS or in moderate inversion at a bias current of 2xIBIAS. The magnitude of RTN can be reduced when the operating range changes from weak inversion to moderate inversion. This bias generation circuit 300 can be modified to modify a transistor operating range of the transistor 301 in the oscillator circuit.

[0048] Fig. 12C shows a bias generation circuit 300 comprising two transistors 301 and 302 with a fixed bias current IBIAS and a switched area of ​​WxL or 2xWxL via a switch SW that, when closed, connects transistors 301 and 302 in parallel. The operable area of ​​the transistor depends on the width-to-length ratio and is in weak inversion at a ratio of W / L and in deeper weak inversion at a ratio of 2xW / L. The size of RTN can decrease by increasing the area, but can also increase because the operating range changes from weak inversion to deeper weak inversion. This circuit may not be a solution to reducing RTN when the transistor area is increased. This bias generation circuit 300 can be modified to generate a transistor operating area of ​​transistors 301 and 302 in the oscillator circuit.

[0049] Fig.Figure 12D shows a bias generation circuit 300 comprising two transistors 301 and 302 with a fixed bias current IBIAS and a switched area of ​​WxL or Wx2xL via a switch SW that, when closed, connects the transistors 301 and 302 in series with a common gate. The operable area of ​​the transistor may depend on the width-to-length ratio and may be in weak inversion at a ratio of W / L and in moderate inversion at a ratio of W / (2xL). The magnitude of RTN may be reduced by increasing the area and may also be reduced by changing the region in which the transistor operates from weak inversion to moderate inversion. This circuit may represent a solution to reducing RTN when the transistor area is increased.This bias voltage generating circuit 300 may be modifiable to modify the operating area of ​​the transistors 301 and 302 in the oscillator circuit. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 344,204

[0001]

Claims

[1] Device comprising: a resistor-capacitor oscillator circuit that can be modified between a first operating mode and a second operating mode, wherein the first operating mode has a first frequency accuracy and a first power consumption, wherein the second operating mode has a second frequency accuracy and a second power consumption, wherein the second frequency accuracy is more accurate than the first frequency accuracy and the second power consumption is higher than the first power consumption; and a control circuit connected to the oscillator circuit to modify the operating mode of the oscillator circuit. [2] The apparatus of claim 1, wherein the first operating mode comprises a weak inversion mode and the second operating mode comprises a weak to moderate inversion mode, wherein in the second operating mode the resistor-capacitor oscillator circuit generates less random telegraph noise than in the first operating mode. [3] Apparatus according to any one of claims 1 to 2, wherein the oscillator circuit comprises two discrete resistor-capacitor oscillators and the control circuit is to modify the operating mode by selecting between the two discrete resistor-capacitor oscillators. [4] The apparatus of any one of claims 1 to 3, wherein the oscillator circuit comprises a programmable resistor-capacitor oscillator having two bias current settings, and the control circuit is operable to modify the operating mode by selecting between the two bias current settings. [5] The device of any one of claims 1 to 4, wherein the oscillator circuit has a third operating mode, the third operating mode having a third frequency accuracy and a third power consumption, the third frequency accuracy being more accurate than the second frequency accuracy and the third power consumption being higher than the second power consumption. [6] The apparatus of claim 5, wherein the third operating mode comprises a moderate to strong inversion mode. [7] Device according to one of claims 5 to 6, wherein the first power consumption is between 60nW and 480nW, wherein the second power consumption is greater than 480nW and less than 1.20µW, and wherein the third power consumption is greater than 1.2µW and less than 3µW. [8] Apparatus according to any one of claims 5 to 7, wherein the third frequency accuracy tolerance is + / - 500 ppm. [9] The device according to any one of claims 1 to 8, wherein the device is a peripheral device and wherein the first operating mode is an advertising state and the second operating mode is a connection state. [10] The device of any one of claims 1 to 8, wherein the device is selected from a low-power peripheral device and a low-power central radio device, and wherein the first operating mode is a radio advertising state, the second operating mode is a radio connection state, and the third operating mode is a radio connection state. [11] Method comprising: Generating a first clock signal with an oscillator circuit in a first operating mode; transmitting a message using the first clock signal; modifying the oscillator circuit from the first operating mode to a second operating mode; Generating a second clock signal with the oscillator circuit in the second operating mode; and Transmitting a message using the second clock signal. [12] The method of claim 11, wherein the first mode of operation comprises an asynchronous communication mode. [13] The method of any one of claims 11 to 12, wherein modifying the oscillator circuit comprises placing the transistors of the oscillator circuit in weak inversion such that the oscillator circuit consumes more than 60nW and less than 480nW of power. [14] The method of any one of claims 11 to 13, wherein the second mode of operation comprises a synchronous communication mode in a peripheral device. [15] The method of claim 14, wherein modifying the oscillator circuit comprises operating the transistors of the oscillator circuit in weak to moderate inversion such that the oscillator circuit dissipates power greater than 480nW and less than 1.20µW. [16] A method according to any one of claims 11 to 15, comprising: modifying the oscillator circuit from the second operating mode to a third operating mode; Generating a third clock signal with the oscillator circuit in the third operating mode; Transmit a message using the third clock signal. [17] The method of claim 16, wherein the third mode of operation comprises a synchronous communication mode in a central device. [18] The method of any one of claims 16 to 17, wherein modifying the oscillator circuit comprises placing the transistors of the oscillator circuit in moderate to strong inversion such that the oscillator circuit consumes more than 1.2µW and less than 3µW of power and meets a frequency accuracy within + / -500ppm. [19] System that has: a power management circuit; a radio circuit electrically connected to the power management circuit, the radio circuit for outputting signals to an antenna; an oscillator circuit electrically connected to the power management circuit, the oscillator circuit being modifiable between a first and a second operating mode, the first operating mode having a first frequency accuracy and a first power consumption, the second operating mode having a second frequency accuracy and a second power consumption, the second frequency accuracy being more accurate than the first frequency accuracy and the second power consumption being higher than the first power consumption; a control circuit electrically connected to the radio circuit, the power management circuit, and the oscillator circuit, the control circuit being operable to modify the operating mode of the oscillator circuit; and a wake-up circuit electrically connected to the oscillator circuit and the power management circuit, the wake-up circuit operable to generate a signal to the power management circuit based at least in part on the operating mode of the oscillator circuit. [20] The system of claim 19, wherein the oscillator circuit comprises two discrete resistor-capacitor oscillators and the control circuit is to modify the mode of operation by selecting between the two discrete resistor-capacitor oscillators. [21] The system of claim 19, wherein the oscillator circuit comprises a resistor-capacitor oscillator having two bias settings, and the control circuit modifies the operating mode by selecting between the two bias settings. [22] The system of claim 20, wherein the oscillator circuit is modifiable to modify a transistor operating range in the oscillator circuit.

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