Differential electromechanical resonant circuits and related methods

Abstract

Differential electromechanical resonant circuit (300) comprising the following: a crystal oscillator that has at least one resonant frequency; a latch coupled to the crystal oscillator; a circuit with a switched capacitor (302) coupled to the latch; and a control circuit arrangement (310) designed to actuate the circuit with switched capacitor (302) at a frequency greater than or substantially equal to the at least one resonant frequency of the crystal oscillator, wherein the circuit with switched capacitor (302) has first and second switches, and wherein the control circuit arrangement (310) is designed for phase-shifted actuation of the first and second switches.

Description

AREA OF REVELATION

[0001] The technology described in the present application relates to oscillators for generating differential oscillating signals. BACKGROUND

[0002] Oscillators are circuits designed to generate oscillating electrical signals, such as sine waves or square waves. Oscillators convert direct current (DC) from a power supply into alternating current (AC) signals. Oscillators are used in a wide variety of electronic devices, including processors, memory, peripherals, digital instruments, and sensor readout circuits.

[0003] US 2014 / 0070897A1 relates to an oscillator circuit comprising first and second resonator terminals for connection to respective terminals of a resonator. The oscillator circuit further comprises a first inverting amplifier coupled between the first and second resonator terminals in a first operating mode, and a back-to-back pair of second inverting amplifiers coupled between the first and second resonator terminals in a second operating mode. A control device is also provided, configured to compare an operating parameter of the oscillator circuit with a switching threshold and toggle the oscillator circuit from the first operating mode to the second operating mode when the operating parameter exceeds the switching threshold.

[0004] Further state of the art is shown in US 2006 / 0 114 074 A1. SUMMARY OF THE REVELATION

[0005] Differential electromechanical resonant circuits according to claim 1 and claim 8, as well as a method for controlling an electromechanical resonant circuit according to claim 14, are presented. Advantageous embodiments are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Various aspects and embodiments of the application are described with reference to the following figures. It is understood that the figures are not necessarily drawn to scale. Elements appearing in several figures are identified in all figures in which they appear by the same reference numeral. Fig. Figure 1 is a block diagram illustrating a quantity detector. Fig. Figure 2A is a block diagram illustrating a resonator according to some non-restrictive embodiments. Fig. 2B is a block diagram showing a differential resonant circuit including the resonator made of Fig. 2A illustrated according to some non-restrictive embodiments. Fig. 2C is a block diagram showing the equivalent circuit made up of Fig. 2B illustrated at low frequencies according to some non-restrictive embodiments. Fig. Figure 3 is a block diagram illustrating another differential resonant circuit according to some non-limiting embodiments. Fig. Figure 4 is a graphical representation showing the frequency response of the resonator. Fig. 2A illustrated according to some non-restrictive embodiments. Fig. 5A is a circuit diagram showing an exemplary circuit with a switched capacitor, which, in conjunction with the differential resonant circuit, Fig. 3 can be used, as illustrated by some non-restrictive examples. Fig. Figure 5B is a graphical representation showing an example differential oscillating signal generated by the differential resonant circuit. Fig. 3 can be output, as illustrated by some non-restrictive examples. Fig. 6A-6C are circuit diagrams that show other circuits with a switched capacitor, which are connected to the differential electromechanical resonant circuit. Fig. 3 can be used, as illustrated by some non-restrictive examples. Fig. Figure 7 is a flowchart illustrating a method for controlling an oscillating circuit according to some non-restrictive embodiments. Fig. 8A is a circuit diagram showing the differential resonant circuit. Fig. 3, when only part of the circuit is activated, as illustrated in some non-restrictive embodiments. Fig. 8B is a block diagram showing a phase-locked loop connected to the switched-capacitor circuit. Fig. 3 is coupled, as illustrated by some non-restrictive examples. Fig. Figure 8C is a graphical representation illustrating a pair of control signals according to some non-restrictive embodiments. Fig. Figure 9A is a block diagram illustrating a differential resonant circuit connected to an electronic circuit according to some non-limiting embodiments. Fig. Figure 9B is a block diagram illustrating a differential resonant circuit connected to an electronic circuit by a transducer, according to some non-limiting embodiments. DETAILED DESCRIPTION

[0007] Aspects of the present application relate to differential electromechanical resonant circuits, including switched-capacitor circuits, configured to prevent low-frequency locking, thereby keeping the resonant circuits in oscillation mode. In oscillation mode, a resonant circuit outputs an oscillating signal—a signal that is periodic at least over a certain time interval. Examples of oscillating signals include sine waves and square waves. Low-frequency locking occurs in some resonant circuits as a result of the oscillator behaving like an open circuit at low frequencies (e.g., frequencies below 100 Hz), which in turn locks the output of the resonant circuit to a constant value. This causes the resonant circuit to leave oscillation mode.

[0008] Aspects of the present application relate to techniques for introducing an impedance into the resonant circuit, wherein the impedance is chosen to prevent the formation of open circuits at low frequencies. In some embodiments, the value of the impedance can be adjusted by appropriately selecting the actuation frequency of the switched-capacitor circuit. In some embodiments, the actuation frequency can be selected from the frequency band of the oscillator or can be at least equal to or greater than a resonant frequency of the oscillator. The differential electromechanical resonant circuits described herein can be used in a variety of contexts where it is desirable to produce differential oscillating signals. Such a context involves circuits that require clock signals or other periodic signals to operate.

[0009] The applicant understands that some resonant circuits tend to generate interference that can significantly degrade the performance of electronic circuits located near the resonant circuit. In some embodiments, interference arises due to the reactive nature of the resonant circuit, causing the oscillating signal to unintentionally couple with other electronic circuits via capacitive and / or inductive coupling. Alternatively or additionally, interference may arise due to the reactive nature of the printed circuit boards on which resonators are typically mounted. Regardless of how it is generated, interference can seriously impair the circuit's ability to perform the functionalities for which it is designed. For example, the circuit made of Fig. Consider Figure 1, which represents a quantity detector. The quantity detector 100 is a circuit for detecting a certain quantity of interest to a user, such as temperature, pressure, velocity, angular motion, etc. In this example, the quantity detector 100 has three channels, 1011, 1012, and 1013. Each channel has a sensor 102 (the sensor type depending on the quantity of interest), an operational amplifier (OA) 104, an analog-to-digital converter (ADC) 106, and an oscillator (Osc) 110. The OA 104 forms a transimpedance amplifier with resistance R. F and converts current signals into voltage signals. The output of each channel is processed using a processor 108. Oscillators 110 generate clock signals Clk, which determine the timing at which ADCs 106 sample the signals detected by sensors 102.

[0010] Due to the capacitive nature of oscillators 110 and / or the circuit board, the clock signals Clk can unintentionally couple with electronic circuits. For example, the clock signal driving the ADC of channel 1013 can unintentionally couple with sensor 102 of channel 1012. This interference can reduce the signal-to-noise ratio of channel 1012, negatively impacting its ability to detect the quantity of interest.

[0011] The applicant has recognized that perturbation in resonant circuits can be attenuated by producing differential—rather than asymmetrical—oscillating signals. The applicant understands that, in fact, the pair of signals constituting a differential signal is typically subject to the same (or substantially the same) perturbation, and that such perturbation can be removed or at least attenuated by subtracting one signal of the pair from the other. Accordingly, aspects of the present application relate to differential resonant circuits.

[0012] Fig. Figure 2A illustrates the equivalent circuit of a resonator that, in some embodiments, can be used to form a differential resonant circuit. In some embodiments, the resonator 200 can include a crystal (e.g., quartz) oscillator. The resonator 200 has a parallel capacitance C. Pand a series capacity C S on. The capacity C S is in series with a resistor R V and an inductance L. However, it is understood that resonators of the types described here can be used in circuit models other than the one in Fig. 2A can embody.

[0013] Fig. Figure 2B illustrates a resonant circuit based on resonator 200. Resonant circuit 201 features resonator 200 and capacitors C. L and inverters 202 and 204. Inverters 202 and 204 are arranged in an antiparallel configuration (where the output of inverter 202 is coupled to the input of inverter 204 and the output of inverter 204 is coupled to the input of inverter 202). Accordingly, inverters 202 and 204 can be considered together as a single latch.

[0014] During operation, inverters 202 and 204 cause the circuit to oscillate within the oscillation frequency band of resonator 200. As a result, a pair of oscillating voltages V is generated. p and V n generated, which represent a differential pair.

[0015] The applicant has recognized that, however, the resonant circuit consists of Fig. 2C suffers from an anomaly referred to here as "low-frequency locking," in which the circuit output locks to a constant value. At low frequencies (such as less than 100 Hz or less than 10 Hz), the capacitors C exhibit P and C S They exhibit high impedances and therefore effectively behave like open circuits. As a result, the Resonator 200 also behaves like an open circuit at these frequencies. This fact is in Fig. Figure 2C illustrates how resonator 200 is effectively an open circuit due to the high impedance of the capacitors. Under these circumstances, inverters 202 and 204 are synchronized, resulting in V n is fixed to the supply voltage and V p is fixed to ground (or vice versa). Consequently, the resonant circuit 201 unintentionally leaves oscillation mode and produces a constant output.

[0016] The applicant has recognized that low-frequency locking can be prevented by placing a switched-capacitor circuit between the output terminals of the resonant circuit and by controlling the switched capacitor within the frequency oscillation band of the resonator. Switched-capacitor circuits of the type described herein can be circuits including at least one capacitor and at least one switch, wherein the at least one switch controls charging and / or discharging of the at least one capacitor. In some embodiments, the capacitor is directly connected to the switch (e.g., without any electrical components in between other than traces or wires). In other embodiments, the capacitor is indirectly connected to the switch (e.g., with one or more electrical components, such as resistors, in between).

[0017] Such a resonant circuit is in Fig. Figure 3 illustrates some non-limiting embodiments. A differential electromechanical resonant circuit 300 comprises a resonator 200, a switched-capacitor circuit (SCC) 302, transistors T1 and T2, current generators 304 and 306, and a control circuit arrangement 310. The resonant circuit 300 produces a differential oscillating signal pair (V p , V n ) at its output terminals. The Resonator 200 and the SCC 302 are each coupled with such output terminals.

[0018] Transistors T1 and T2 are arranged in an antiparallel configuration, with the drain of T1 coupled to the gate of T2 and vice versa, although other antiparallel configurations are also possible. Therefore, transistors T1 and T2 can be considered a latch. Transistors T1 and T2 can be implemented using any suitable type of transistor, including, but not limited to, field-effect transistors (FETs), metal-oxide-semiconductor (MOS) transistors, and bipolar junction transistors (BJTs).

[0019] In some embodiments, a pair of inverters, as in Fig. Figure 2B illustrates how transistors T1 and T2 can be used to form a latch. Alternatively or additionally, any other bistable circuit can be used to form a latch. Transistors T1 and T2, together with resonator 200, cause resonant circuit 300 to oscillate. As a result, the signals V oscillate p and V n with essentially opposite quantities, periodically.

[0020] The SCC 302 is designed to prevent low-frequency locking of transistors T1 and T2. Specifically, the SCC 302 provides an impedance in parallel with that of resonator 200 between the output terminals of resonant circuit 300. The SCC 302 is designed such that its impedance at low frequencies is lower than the impedance of resonator 200 at the same frequencies. The presence of this impedance prevents the formation of an open circuit between the output terminals. Given the frequency-dependent nature of the capacitor's impedance, the impedance of the SCC 302 can be adjusted by selecting the frequency at which its switch(es) are actuated. A control circuit arrangement 310 controls the actuation frequency of the SCC 302.

[0021] In some embodiments, the control circuit arrangement 310 actuates the SCC 302 at a frequency selected from within the oscillation band of the resonator 200. Fig. Figure 4 is a graphical representation illustrating the amplitude response of a resonator 200. In this example, the resonator 200 exhibits two resonant frequencies: f s and f p The oscillation band of resonator 200 is, in this example, the band between f s and f p (including f s and f p ) defined. The frequency f s (which is referred to as a "series resonant frequency") represents the frequency at which the series capacitor C S (see Fig. 2A) resonates and the frequency f p (which is referred to as a "parallel resonant frequency") represents the frequency at which the parallel capacitor C p (see Fig. 2A) resonates. Under other circumstances, however, the frequency f s greater than the frequency f p this is because not all embodiments respond to the answer from Fig. 4 are limited.

[0022] In some embodiments, the control circuit arrangement 310 actuates the SCC 302 at a frequency greater than at least one of the resonant frequencies of the resonator 200. For example, the control circuit arrangement 310 can actuate the SCC 302 at a frequency greater than the lowest resonant frequency (f s in the example from Fig. 4) of the resonator 200 is, that is, greater than the second lowest resonance frequency (f p in the example from Fig. 4) of the resonator 200 or, if the resonator 200 exhibits more than two resonant frequencies, greater than any other resonant frequency. The applicant has recognized that actuating the SCC 302 at a frequency greater than at least one of the resonant frequencies of the resonator 200 produces a sufficiently low impedance to prevent low-frequency locking.

[0023] According to some non-restrictive embodiments, the SCC 302 can be implemented in any suitable way, for example including the circuit made of Fig. 5A, implemented. In some embodiments, the SCC can be symmetrical, so that the SCC has the same impedance regardless of which output terminal of V is used. p or from the output port of V n is seen in the circuit. Fig. For example, terminal 5A sees both output terminals: 1) a switch S1 coupled in series with a switch d, with a capacitor C1 between switches S1 and d, and 2) a switch S2 coupled in series with a switch d, with a capacitor C2 between switches S2 and d. The presence of a symmetrical circuit can prevent unwanted imbalances in the output signal.

[0024] Alternatively or additionally, symmetry of the circuit with a switched capacitor can be ensured by actuating switches S1 and S2 with essentially opposite phases. Fig. 5B, the V n and V p An example illustrating how the voltage changes over time is shown by switching S1 and S2 with essentially opposite phases. When switching S1 is actuated (set to its conductive state), the signal V pAt a certain value (in this example V1) the signal is sampled and the signal V is generated. n The signal is sampled at the opposite value (in this example -V1). Furthermore, when switches S2 are actuated, the signal V is also sampled. n The value V1 is sampled and the signal V is generated. p The opposite value, -V1, is sampled. Actuating the switches in this manner ensures that the electrical charge is distributed symmetrically between the capacitors, thus preventing unwanted imbalances in the differential output signal. Switch d is activated once per cycle to reset the state of the capacitors.

[0025] Other examples of switched-capacitor circuits are in Fig. 6A-6C are illustrated according to some non-restrictive examples. In each of these circuits, the output terminal of V is nThe circuit shown is essentially the same as that of the output terminal of V. p circuit shown. The circuit consists of Fig. 6A has two switches S1, two switches S2, two switches d, two capacitors C1 and two capacitors C2. The circuit consists of Fig. 6B has two switches S1, two switches S2, one capacitor C1 / 2 and one capacitor C2 / 2. The circuit consists of Fig. The 6C has two switches S1, two switches S2, one capacitor C1 / 2, and one capacitor C2 / 2. It should be understood that the SCC 302 is not limited to any of the implementations described here, as other implementations can be used.

[0026] The applicant has recognized that a challenge lies in the manner in which the SCC 302 is actuated, as described above. Actuating the SCC 302 may involve producing an actuation signal with a frequency selected from the oscillation frequency band of the resonator 200 (or otherwise chosen to be greater than one of the resonant frequencies). However, such a signal is not available until oscillation has been established in the resonant circuit. Putting the resonant circuit into oscillation mode simultaneously involves actuating the SCC 302 because otherwise the resonant circuit may experience low-frequency locking. In other words, the generation of the actuation signal depends on the existence of oscillation in the resonant circuit, and the existence of oscillation depends on the actuation signal to prevent low-frequency locking.In some embodiments, this puzzle is solved using the initialization procedure from . Fig. 7 solved.

[0027] Fig. Figure 7 is a flowchart illustrating a method for controlling an electromechanical resonant circuit according to some non-limiting embodiments. In some embodiments, the method 700 for controlling the electromechanical resonant circuit can be derived from Fig. 3 can be used and can be carried out using the control circuit arrangement 310. However, it is understood that the method 700 can be used to control any other suitable type of differential resonant circuit.

[0028] Method 700 begins at stage 702, where a controller activates the first part of the latch of an electromechanical resonant circuit to produce an asymmetrical oscillating signal. Referring to, for example, Fig. 3 The control circuit arrangement 310 can activate one of the transistors T1 and T2, but not both, to produce an asymmetrical oscillation signal. Fig. Figure 8A illustrates a scenario in which only one transistor (T2) is activated, while the other transistor (T1) is deactivated. This results in the generation of an asymmetrical oscillation signal (V). n ) with a frequency in the oscillation band of the resonator 200.

[0029] At stage 704, the controller generates a first and second control signal based on the asymmetrical oscillation signal from stage 702. Now, with reference to Fig. In some embodiments, the control signals can be generated using a phase-locked loop (PLL). In this example, the asymmetric oscillation signal generated at stage 702 is provided as input to a PLL 800, which in turn generates a pair of control signals S. c1 and S c2The PLL 800 can be implemented in any suitable way, including, for example, with a phase frequency detector (PFD) 802 and a voltage-controlled oscillator (VCO) 804, as shown in Fig. The PLLs are arranged as shown in Figure 8B. Other PLL implementations are also possible. The PLL 800 can be part of the control circuit arrangement 310.

[0030] In some embodiments, the PLL 800 is configured to receive control signals S c1 and S c2 to generate waves that are phase-shifted relative to each other. Fig. Figure 8C is a graphical representation illustrating a pair of phase-shifted signals. In this example, the two control signals are periodic with a periodicity T (where the periodicity T can be equal to the inverse of a frequency in the oscillation band of resonator 200). The control signal S c1 exhibits pulses at t=0, t=T, t=2T, etc. The control signal S c2It exhibits pulses at t=T / 2, t=3T / 2, t=5T / 2, etc. Therefore, the control signals are delayed relative to each other by T / 2, which corresponds to a π-phase shift.

[0031] At stage 706, the controller operates the switched-capacitor circuit of the resonant circuit using the first and second control signals. For example, the control signals S c1 and S c2 control the SCC 302. Again with reference to Fig. 5A can be the control signal S c1 control the actuation of switches S1 and can transmit the control signal S c2 The actuation of switches S2 is controlled. Consequently, each switch can be set to its conductive state for the duration of the received pulse and can be set to its non-conductive state outside of the pulse. A (in Fig. 8B (not shown) another control signal can control the actuation of switches d. The circuits with switched capacitor from Fig. 6A-6C can be controlled in a similar way.

[0032] At level 708, the controller activates a second part of the latch to produce a differential oscillation signal. Again, referring to Fig. 3. The control circuit arrangement 310 can activate transistor T1 at stage 702 (in addition to transistor T2, which is already activated at stage 702). As a result, a differential oscillation signal pair (V) is generated. p and V n ) generated.

[0033] Differential resonant circuits of the types described here can be used in a variety of contexts, for example to time the operations of one or more electronic circuits. Fig. Figure 9A is a block diagram illustrating a differential resonant circuit 300 connected to an electronic circuit 900. The resonant circuit 300 can supply a differential oscillating signal (in this example, a sine wave) to the electronic circuit 900. The differential oscillating signal can time the operations of the electronic circuit 900 or can otherwise provide a reference signal. In some embodiments, signal converters can be used to convert differential sine waves into other types of periodic waves, such as square waves, triangle waves, and sawtooth waves. Fig.Figure 9B is a block diagram illustrating a resonant circuit 300 connected to an electronic circuit 900 via a converter 902. In this example, the converter 902 converts a differential sine wave into a differential square wave. The converter 902 can be implemented in any suitable way, including, for example, with a comparator or a Schmitt trigger circuit. The differential square wave can be used as a clock signal to time the operations of the electronic circuit 900.

[0034] The electronic circuit 900 can incorporate any number of systems, including processors, memory, analog-to-digital converters, peripheral devices, I / O ports, laboratory equipment (e.g., oscilloscopes, spectrum analyzers, vector network analyzers, signal generators, digital pattern generators, pseudorandom bit sequence generators, pulse generators, cable testers, and frequency counters, among others), receivers and transmitters for wired and wireless communications (digital or analog communications), signal mixers, digital clocks, automatic test equipment, and readout circuitry for a variety of sensors (e.g.,(Including accelerometers, gyroscopes, temperature sensors, pressure sensors, heart rate sensors, acoustic sensors, ultrasonic sensors, light sensors, infrared sensors, speed sensors, carbon dioxide sensors, nitrogen oxide sensors, pH sensors, flow sensors, anemometers, gas sensors, altimeters, air velocity sensors, depth sensors, impact sensors, free-fall sensors, gravity sensors, odometers, piezoelectric sensors, position sensors, GPS sensors, laser sensors, current meters, electrometers, resistance meters, voltage meters, multimeters, time-of-flight sensors and proximity sensors, among others).

[0035] A special context involves lidar systems, in which a differential resonant circuit can be used, among other functionalities, to time the operations of the readout circuit for a time-of-flight sensor or to time the operations of a phased optical array.

[0036] Aspects of the technology described here can provide one or more advantages, some of which have been described previously. Some examples of such advantages are now described. It is understood that not all aspects and embodiments necessarily provide all of the advantages now described. Furthermore, it is understood that aspects of the technology described here may provide additional advantages beyond those now described.

[0037] Aspects of the technology described here provide resonant circuits that, compared to other types of resonant circuits, reduce interference with adjacent circuits. Further aspects of the technology described here provide differential resonant circuits to limit the negative effects of low-frequency locking.

[0038] The terms "approximately", "essentially", and "about" can be used to mean, in some embodiments, within ±20% of a target value, in some embodiments within ±10% of a target value, in some embodiments within ±5% of a target value, and in some embodiments within ±2% of a target value. The terms "approximately", "essentially", and "about" can include the target value.

[0039] One aspect is the design of differential electromechanical resonant circuits. These circuits can be used in a variety of contexts to produce differential oscillating signals, such as sine waves or square waves. A switched capacitor circuit (SCC) is used to prevent low-frequency locking, which would otherwise cause the resonator output to lock into a constant value. Specifically, the SCC provides an impedance in parallel with the resonator between the output terminals of the resonant circuit. The SCC is designed such that its impedance is lower than the resonator's impedance at low frequencies. The presence of this impedance prevents the formation of an open circuit between the output terminals, thus keeping the resonant circuit in oscillatory mode.The differential electromechanical resonant circuits described here can be used to produce clock signals or otherwise to produce periodic reference signals.

Claims

[1] Differential electromechanical resonant circuit (300) comprising the following: a crystal oscillator that has at least one resonant frequency; a latch coupled to the crystal oscillator; a circuit with a switched capacitor (302) coupled to the latch; and a control circuit arrangement (310) designed to actuate the circuit with switched capacitor (302) at a frequency greater than or substantially equal to the at least one resonant frequency of the crystal oscillator, wherein the circuit with switched capacitor (302) has first and second switches, and wherein the control circuit arrangement (310) is designed for phase-shifted actuation of the first and second switches. [2] Differential electromechanical resonant circuit (300) according to claim 1, further comprising a first output terminal and a second output terminal, wherein the crystal oscillator is configured to generate a differential oscillation signal pair at the first and second output terminals. [3] Differential electromechanical resonant circuit (300) according to claim 2, wherein the crystal oscillator, the latch and the switched capacitor circuit (302) are each coupled to both the first and second output terminals. [4] Differential electromechanical resonant circuit (300) according to one of claims 1 to 3, wherein the latch has a first and second transistor (T1, T2) arranged in an antiparallel circuit. [5] Differential electromechanical resonant circuit (300) according to claim 4, wherein a gate of the first transistor (T1) is coupled to a drain of the second transistor (T2) and a gate of the second transistor (T2) is coupled to a drain of the first transistor (T1). [6] Differential electromechanical resonant circuit (300) according to one of claims 1 to 5, wherein the at least one resonant frequency is a series resonant frequency of the crystal oscillator. [7] Differential electromechanical resonant circuit (300) according to one of claims 1 to 6, wherein the control circuit arrangement (310) is further configured as follows: Activating the first part of the latch to produce an asymmetrical oscillation signal; Generating a first and second control signal based on the asymmetrical oscillation signal; Control of the switched-capacitor circuit (302) using the first and second control signals; and Activating a second part of the latch to produce a differential oscillation signal. [8] Differential electromechanical resonant circuit (300) comprising the following: a crystal oscillator; a latch coupled to the crystal oscillator; a circuit with a switched capacitor (302) coupled to the latch and comprising a switch; and a phase control loop coupled to the switch and the latch, wherein the phase control loop is configured to actuate the switch. [9] Differential electromechanical resonant circuit (300) according to claim 8, wherein the switch is a first switch and the circuit with switched capacitor (302) further comprises a second switch, wherein the phase control loop is configured for phase-shifted actuation of the first and second switches. [10] Differential electromechanical resonant circuit (300) according to claim 8 or 9, further comprising a first output terminal and a second output terminal, wherein the crystal oscillator is configured to generate a differential oscillation signal pair at the first and second output terminals. [11] Differential electromechanical resonant circuit (300) according to claim 10, wherein the crystal oscillator, the latch and the switched capacitor circuit (302) are each coupled to both the first and second output terminals. [12] Differential electromechanical resonant circuit (300) according to one of claims 8 to 11, wherein the latch has a first and second transistor (T1, T2) arranged in an antiparallel circuit. [13] Differential electromechanical resonant circuit according to claim 12, wherein a gate of the first transistor (T1) is coupled to a drain of the second transistor (T2) and a gate of the second transistor (T2) is coupled to a drain of the first transistor (T1). [14] Method (700) for controlling an electromechanical resonant circuit (300), wherein the method comprises: Activating a first part of a latch to produce an asymmetric oscillation signal, where the latch is coupled to a crystal oscillator; Generating a first and second control signal based on the asymmetrical oscillation signal; Controlling a switched-capacitor circuit (302) using the first and second control signals; and Activating a second part of the latch to produce a differential oscillation signal, where controlling the circuit with switched capacitor (302) with the first and second control signals has the following characteristics: Activating a first switch of the circuit with switched capacitor (302) with the first control signal; and Activating a second switch of the circuit with switched capacitor (302) with the second control signal. [15] Method (700) according to claim 14, wherein the generation of the first and second control signals comprises generating the first and second control signals such that they are phase-shifted relative to each other. [16] Method (700) according to claim 14 or 15, wherein the generation of the first and second control signal comprises: Supplying the asymmetrical oscillation signal to an input of a phase-locked loop; and Generating the first and second control signals using the phase-controlled loop. [17] Method (300) according to any one of claims 14 to 16, wherein activating a first part of the latch comprises activating a first transistor (T1) of the latch and wherein activating a second part of the latch comprises activating a second transistor (T2) of the latch, wherein the first and second transistors (T1, T2) are arranged in an antiparallel circuit. [18] Method (700) according to any one of claims 14 to 17, wherein the activation of the first part of the latch precedes the activation of the second part of the latch.

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