LOW VARIATION QUICK-START CRYSTAL OSCILLATOR

Abstract

Oscillation circuit, including: a crystal oscillator structure; and a boost circuit configured to induce oscillation in the crystal oscillator structure, wherein the boost circuit is configured to excite the crystal oscillator structure with an excitation signal having a frequency that varies from an initial frequency to an end frequency, the initial frequency and the end frequency defining a frequency band, and where a resonance frequency of the crystal oscillator structure is located within the frequency band, the boost circuit includes the following: a current ramp circuit configured to produce a current that varies between an initial current and a final current; and an oscillator circuit coupled to the current ramp circuit and configured to generate an oscillator signal having a frequency that varies based on a variation of the current, wherein the frequency of the oscillator signal varies from the initial frequency to the final frequency according to the initial current and the final current, respectively. where the current, which varies between the initial current and the final current, increases in an essentially linear manner.

Description

AREA

[0001] The present invention relates to a circuit for inducing oscillations in a crystal oscillator structure or other oscillation system and to a corresponding method. BACKGROUND

[0002] Many electrical circuits use a reference frequency signal for various purposes. If an accurate and frequency-stable reference frequency is required, a high-Q (quality factor) oscillator, such as a crystal or a similar oscillator structure, is typically used. These oscillator types typically have a long start-up time, which affects the service life of battery-powered systems.

[0003] The publication by Iguchi, Shunta et al.: "92% start-up time reduction by variation-tolerant chirp injection and negative resistance booster (NRB) in 39MHz crystal oscillator" In: 2014 symposium on VLSI circuit digest of technical papers. Honolulu, HI: IEEE, 2014, pp. 1-2, ISBN 978-1-4799-3328-0 discloses a 92% reduction in start-up time through variation-tolerant chirp injection and negative resistance booster (NRB) in a 39 MHz crystal oscillator.

[0004] An object of the present application is to provide an improved oscillation circuit with reduced start-up time.

[0005] This task is carried out by the independent the scope of protection is defined by the appended claims BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing a boost circuit for starting an oscillation system according to an embodiment of the invention. Fig. 2 is a block level diagram showing various circuits together which are configured to provide the boost circuit of Fig. 1 according to an embodiment of the disclosure. Fig. 3 is a diagram illustrating a current ramp signal according to an embodiment of the disclosure. Fig. 4 is a schematic diagram showing a circuit configured to generate a current ramp signal according to an embodiment of the disclosure. Fig. Figure 5 is a schematic diagram showing an oscillator circuit configured to receive a current ramp signal and generate a variable frequency output signal to be used as an excitation signal for the oscillating system of Fig. 1 according to one embodiment of the disclosure. Fig. 6 is a diagram illustrating a triangular voltage waveform showing a changing voltage slope corresponding to the current ramp signal according to one embodiment of the disclosure. Fig. Figure 7 is a graph showing the start-up time for an oscillating system that does not use a boost circuit. Fig. 8 is a graph illustrating the start-up time for an oscillation system using a boost circuit according to an embodiment of the disclosure. Fig. 9 to 11 are flow diagrams illustrating various steps in establishing a stable reference frequency in an oscillating system according to an embodiment of the disclosure. DETAILED DESCRIPTION

[0006] The present invention will now be described with reference to the accompanying drawings, in which like elements are designated by like reference numerals throughout and the structures and devices shown are not necessarily to scale.

[0007] Systems, methods, apparatus, and embodiments are provided that quickly and efficiently provide a stable reference frequency.

[0008] As mentioned above, crystal oscillators are often used as frequency references in various types of electrical circuits. Typically, an oscillator structure is excited via noise to its resonant oscillation frequency. The time required for the crystal oscillator structure to reach its stable resonant oscillation frequency is sometimes referred to as the "oscillation buildup time."

[0009] In the case of quartz crystals as crystal oscillator structures, the oscillation setup time can exceed 3 ms, and significant variation in oscillation setup time due to tolerances caused by variable noise may require a design to wait up to 10 ms to ensure a stable reference frequency is established under all conditions. The long "initial" start-up time, along with their additional wait bandwidth, can result in reduced battery life in portable applications. Conventional crystal oscillators are therefore often compromised by trade-offs between start-up time, start-up variation, and circuit power consumption.

[0010] The present disclosure relates to a crystal oscillator structure and a boost circuit configured to excite the crystal oscillator to rapidly reach its stable resonant frequency, thus reducing both the oscillator start-up time and the start-up time variability. The boost circuit is configured to generate an excitation signal having a frequency that varies between an initial frequency and a final frequency. The frequency range between the initial frequency and the final frequency defines a frequency band, with the resonant frequency of the crystal oscillator structure lying within the frequency band. Using the excitation signal with the varying frequency results in a faster oscillation build-up of the crystal oscillator structure because the target stimulus oscillates at a significant signal amplitude at the resonant frequency, thus introducing energy into the crystal.Consequently, the oscillation of the crystal oscillator structure will not start due to noise and the large fluctuation of the oscillator start-up time will be greatly reduced.

[0011] In one embodiment of the disclosure, in a method of starting or inducing operation of a crystal oscillator structure, a frequency ramp excitation signal is generated and applied to the crystal oscillator structure. The frequency ramp excitation signal causes the crystal oscillator structure to oscillate at its resonant frequency, since the resonant frequency of the crystal oscillator structure is a frequency that lies within a frequency range covered by the frequency ramp excitation signal. Consequently, after a pass through the frequency ramp excitation, energy is introduced into the crystal oscillator structure. After the pass, the boost circuit generating the frequency ramp excitation signal is turned off, and the crystal oscillator structure continues to oscillate via an oscillator circuit in which the crystal oscillator structure is incorporated.In one embodiment, the oscillator circuit comprises a Pierce-type oscillator, but other oscillator circuits may be used and any alternative oscillator circuits may be used and are considered to be within the scope of the present invention.

[0012] As for the characters, Fig. 1 is a simplified schematic diagram of an oscillator circuit 10 including a crystal 12 in an oscillator circuitry 14, such as a Pierce oscillator. The oscillator circuit 10 further includes a boost circuit 16 coupled to the oscillator circuitry 14. The boost circuit 16 is configured to generate an excitation signal 18 that can establish a stable reference frequency of the crystal oscillator structure at its resonant frequency. In the exemplary embodiment of Fig. 1, the oscillator circuitry 14 comprises a Pierce oscillator with an inverter 20 that receives the excitation signal 18. A series resistor 22 is connected in parallel with the inverter 20 and biases the inverter 20 in its linear operating region, causing the inverter to function as a high-gain inverting amplifier. The crystal oscillator structure 12 is connected in parallel with the resistor 22 and the inverter 20 and forms the terminals Xin, Xout of the oscillator circuit 10. The circuit 10 further includes two capacitors 24, 26 connected between the terminals Xin, Xout, and a reference potential 28, such as ground. The crystal structure 12, in combination with the capacitors 24 and 26, forms a bandpass filter and provides a 180° phase shift and a voltage gain from the output Xout to the input Xin in a small region around the resonant frequency of the crystal.

[0013] As in Fig. 1, the excitation signal 18 from the boost signal comprises a frequency ramp that runs from an initial frequency f1 to a final frequency f n varies, whereby the value defined by f1 and f n defined frequency range defines a frequency band. In one embodiment, f1 < f n and the frequency ramp comprises a signal with an increasing frequency. In another embodiment, f1 > f n and the frequency ramp of the excitation signal has a decreasing frequency. Furthermore, in one embodiment, the frequency ramp generally increases or decreases linearly, but nonlinear frequency variations are also within the scope of the disclosure.

[0014] Fig. 2 is a schematic diagram illustrating an exemplary embodiment of the boost circuit 16 of Fig. 1 in more detail. The boost circuit 16 includes a current ramp circuit (i.e., a current ramp generator) 30 and a current-controlled oscillator circuit (e.g., a current-controlled RC oscillator) 32. The boost circuit 16 further includes a tristate buffer 34 and a decoupling capacitor 35. Upon receipt of a boost enable signal (en boost) 36, the current ramp generator 30 is enabled. The current ramp circuit 30 is configured to generate a current ramp signal 38 that varies from a first initial current value I1 to a second final current value I2. In one embodiment, the current ramp signal 38 varies from the first initial current value I1 to the second final current value I2 over a time period t2-t1, as shown in Fig. 3. In the Fig. 3, I1 < I2 and the current of the current ramp signal increases in a substantially linear manner, resulting (as will be explained in more detail later) in a frequency ramp signal whose frequency increases. Furthermore, as will also be seen later, the frequency ramp signal 18 increases from Fig. 1 from its initial frequency at t1 to its final frequency at t2 (including a plurality of pulses with different frequencies during the time period t2-t1).

[0015] Further with regard to Fig. 2, the RC oscillator circuit 32 receives the current ramp signal 38 from the current ramp circuit 30 and a control signal 40 (e.g., control 1) that starts and stops the RC oscillator circuit 32, respectively. In one embodiment, the current ramp circuit 30 outputs a second control signal 42 (e.g., control 2) that drives a tristate buffer 34 that receives an output 44 of the RC oscillator circuit 32 and selectively supplies the output signal 44 to the oscillator circuitry 14 comprising the crystal oscillator structure 14 of Fig. 1. In the manner described above, the tristate buffer 34, according to one embodiment, serves as a switch to selectively stimulate the crystal oscillator structure 12 only during an actual ramp-like rise.

[0016] Fig. 4 is a schematic circuit diagram illustrating in more detail one embodiment of a current ramp circuit 30 according to the present disclosure. The current ramp circuit 30 receives a reference bias current Ibias_in at an input 50, where Ibias_in serves as a reference current for a group of current mirror taps. For example, a minimum current portion 52 of the current ramp circuit 30 generates the initial current I1, which is generally equal to Ibias_in (or otherwise proportional to the bias current), based on the width-to-length (W / L) ratio between the bias current mirror transistor 54 and the minimum current mirror tap transistor 56. This initial current I1 is mirrored as the Iramp current to the output mode 40. Alternatively, and preferably, in one embodiment, the Ibias path is open when the boost circuit is deactivated, so that the initial current I min= 0, which allows lower power consumption, and then jumps to I1 when the boot circuit is activated, as in Fig. 3 shown.

[0017] Normally, when disabled, current ramp circuit 30 receives the en boost signal high (H), which turns on a start transistor 58, discharging a capacitor 60 and turning off NMOS devices 64, 66, and 68. When the en boost signal at 36 goes low (L), transistor 58 turns off. Current from ratio-3 transistor 70 causes a gradual charging of capacitor 60, increasing node 62 and subsequently the Iramp current 40 based on a counter conductance of transistor 72.

[0018] When transistor 64 begins conducting due to charging of capacitor 60, which increases node 62 voltage, the voltage at node 74 decreases, causing a ramp-on comparator 76 to trigger and the ramp-on signal to go high, indicating the beginning of the current ramp period. As capacitor 60 continues to charge, transistor 66 also begins conducting, node 78 also begins to be pulled low, and due to the lower threshold of the ramp-on comparator 80, the ramp-on comparator 80 is triggered and goes high, indicating the end of the current ramp. Thus, if the ramp-on signal is high and the ramp-on signal is low, the current is about to rise. When both the ramp-on and ramp-on signals are high, the current ramp is over.

[0019] The oscillator circuit 32 of the boost circuit 16 of Fig. 2 is in Fig. 5 according to one embodiment of the disclosure. Initially, at a HIGH level, the oscillator circuit 32 in one embodiment comprises an RC oscillator circuit and has a voltage reference generation circuit 90 that provides a reference voltage v_ref to a pair of comparator circuits CMP1 92 and CMP2 94. The ramp current Iramp 38 is supplied by the current ramp generator 30 of Fig. 4 and mirrored via a current mirror circuit 96 (M1 and M2) to generate a charging current I charge98. Based on a triggering of comparators 92 and 94, the charging current 98 is alternatively directed to the first and second ramp capacitors 100, 102. As described in more detail below, the comparators 92 and 94 act in conjunction with the SR flip-flop 104 to alternately switch the ramp capacitors 100, 102 between a charging mode and a discharging mode. Furthermore, as the ramp current 38 increases, the charging current 98 increases, which in turn causes the charging rate of the capacitors to increase. The increased charging rate of the capacitors 100, 102 is then used to generate a voltage signal whose frequency increases in accordance with the current ramp signal 38.

[0020] More specifically, the RC oscillator 32 receives the Iramp current signal 38, which is composed of the reference or minimum current portion consisting of I1 and the variable portion consisting of the variable portion that varies between 0 and I2-I1. In the manner described above, the ramp current varies between the values ​​I1 and I2. In this example, the ramp current signal 38 increases in a generally linear manner, but other variations are possible and fall within the scope of the present disclosure. The ramp current I ramp 38 is mirrored via a current mirror circuit 96, which is composed of transistors M1 and M2, to form the charging current 98, where I charge 98 a ratio of I ramp 38 based on the relative width-to-length ratios of transistors M1 and M2. The charging current I charge98 is conducted along one of two conduction paths based on a state of switches S1, S1(bar) and S2, S2(bar). The on / off state of switches S1 and S2 is determined by control signals q and qn, which are outputs of an SR flip-flop 104. When the reset output of flip-flop 104 is HIGH (qn = H and q = L), S1(bar) switch 116 is closed and S2(bar) switch 108 is open, while S1 switch 110 is open and S2 switch 112 is closed. In this configuration, the charging current I charge 98 the first charging capacitor, while the S2 switch 112 ensures that the second charging capacitor C2 is discharged. This causes the voltage at the ramp1 node to rise while the first capacitor is charging, with the extent to which the ramp1 node rises being a function of the magnitude of the charging current I charge 98 (and thus also a function of the ramp current 38).

[0021] As soon as the voltage on the ramp exceeds the reference voltage v_ref, the first comparator 92 is triggered and the resulting voltage at cmp1 causes the flip-flop 104 to be set, so that q is now HIGH and qn is LOW. This causes the S1(bar) switch 110 to close and the S2 switch 112 to open. In this switching configuration, the first charging capacitor C1 is discharged by S1 110, while the second charging capacitor C2 is charged with the charging current I charge 98 is charged by S2(bar) 108. It should be noted that since the charging current 98 ramps up, the charging current for C2 is greater in this embodiment than previously for charging C1, causing the rate at which the voltage at the ramp2 node increases to be greater than the rate at which ramp1 previously increased. Consequently, the voltage at ramp2 triggers the second comparator 94 more quickly, and thus the flip-flop 104 is reset more quickly. A combination of the voltages at ramp1 and ramp2 is shown in Fig. 6 as an example. It can be seen that for three exemplary cycles, the gradient of each subsequent voltage ramp increases, with slope3 > slope2 > slope1, which corresponds to the higher charging rate due to a higher charging current. The resulting voltage ramp signal of Fig. 6 is then fed into the comparators 92 and 94 of Fig. 5 which drive the set / reset inputs of the SR flip-flop 104, resulting in a generally square waveform whose frequency varies in a manner corresponding to the changing charging rate of the capacitors 100 and 102 in Fig. 5 corresponds.

[0022] Thus, it can be seen how the resulting signal 116 at the output (e.g., the output of a buffer 114) represents a square wave signal having a frequency that varies (e.g., increases) in a manner corresponding to the current ramp signal 38, with the initial frequency of the output (i.e., the excitation signal 18 of Fig. 1) I1 corresponds to (e.g. a non-zero current) and the highest and final frequency corresponds to I2.

[0023] As highlighted above, the excitation signal 18 (ie signal 116 of Fig. 5) is configured to vary between two frequency values ​​that define a frequency band in which the resonance frequency of the crystal structure 12 is located. Consequently, the ramp current 38 of Fig. 3 (which is e.g. by the circuit 30 of Fig. 4) is configured to vary between two current values ​​I1 and I2 that ensure the above-mentioned frequency range. In an advantageous embodiment, the frequency range of the excitation signal 18 around the expected or estimated resonant frequency of the crystal structure 12 is relatively narrow, but varying range sizes may be employed, as contemplated by the present disclosure.

[0024] Some of the advantages of the boost circuit of the present invention are evident when comparing Fig. 7 and Fig. 8. In Fig. 7 shows that approximately 120 microseconds pass between the initial start-up of the crystal and the time at which it reaches a truly stable oscillation point, as in the case of a conventional type of crystal oscillator circuit that uses noise for start-up. In contrast, Fig. 8 a time span of approximately 45 microseconds between the start of the boost circuit and the establishment of a stable oscillation or reference frequency, which in this example corresponds to a nearly 3-fold reduction. As in Fig. 7 and Fig. 8, the boost circuit of the present disclosure further consumes Fig. 8 consumes less power during the boot-up period, resulting in an improvement in reducing power consumption.

[0025] The present disclosure further includes a method for inducing oscillations in a crystal oscillator structure. Fig. 9 is, in particular, a flowchart illustrating such a method 150.

[0026] While the method is illustrated and described below as a series of acts or events, the illustrated ordering of such acts or events is not to be considered limiting. For example, such acts may be performed in a different order and / or concurrently with other acts or events than those shown and / or described herein. Further, not all of the illustrated acts may be required to practice one or more aspects or embodiments of this disclosure. Further, one or more of the illustrated acts may be performed in one or more separate acts and / or stages.

[0027] At 152 of Fig. 9, an act of activating a boost circuit to generate a frequency output signal occurs. The generated frequency output signal varies from an initial frequency to a final frequency, thereby defining a range of frequencies. The method begins at 154 by applying the frequency output signal to the crystal oscillator structure, wherein a resonant frequency of the crystal oscillator structure is within the frequency range defined by the boost circuit. At 155, the boost circuit is deactivated after the resonant frequency has been established in the crystal oscillator structure. In one embodiment, the boost circuit may be deactivated by turning off the power supply to the circuit, interrupting its output to the crystal oscillator structure, or driving its timer after the resonant frequency has been reached and is stable.

[0028] Fig. 10 is a flowchart illustrating the generation of the frequency output signal in more detail according to one embodiment. The act 152 of Fig. 9 may include activating a current ramp circuit to generate a current ramp signal at 156 that includes a current that varies between an initial current and a final current. In one embodiment, the current ramp signal includes a current that varies in a substantially linear manner between the initial current and the final current, but the method is not so limited. At 158 ​​of Fig. 10, the method includes supplying the current ramp signal to a current controlled oscillator circuit to generate the frequency output signal based on the current ramp signal using the oscillator circuit.

[0029] With respect to the action 158, generating the frequency output signal with the current ramp signal using the oscillator circuit in Fig.11 at 160 with the charging of a capacitance element using the current ramp signal and the discharging of the capacitance element each time a voltage in the capacitance element reaches a threshold voltage during charging at 162. The continued charging and discharging of the capacitance element using the current ramp signal results in a substantially triangular voltage waveform across the capacitance and a rectangular waveform after the SR flip-flops reach a frequency that varies in a manner corresponding to the current ramp signal varying between the initial current and the final current. Generating the frequency output signal further includes, at 164, using the voltage in the capacitance element to drive comparators to generate a square wave signal having a frequency that varies within a frequency range.The resulting frequency output signal is the excitation signal used by the boost circuit to build the resonant frequency of the crystal structure.

[0030] With particular regard to the various functions performed by the components or structures (assemblies, devices, circuits, systems, etc.) described above, the terms used to describe such components (including a reference to a "means") are intended to correspond to any component or structure that performs the specified function of the described component (e.g., that is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the implementations of the invention illustrated herein as examples. Moreover, although a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired or advantageous for any particular application.Furthermore, the terms “including”, “includes”, “having”, “comprising”, “having” or “with” or variants thereof, when used in the detailed description on the one hand and in the claims on the other, are to be understood as inclusive, similar to the term “comprising”.

Claims

[1] Oscillation circuit comprising: a crystal oscillator structure; and a boost circuit configured to induce oscillation in the crystal oscillator structure, wherein the boost circuit is configured to excite the crystal oscillator structure with an excitation signal having a frequency varying from an initial frequency to a final frequency, the initial frequency and the final frequency defining a frequency band, and wherein a resonance frequency of the crystal oscillator structure is located within the frequency band, wherein the boost circuit comprises: a current ramp circuit configured to generate a current that varies between an initial current and a final current; and an oscillator circuit coupled to the current ramp circuit and configured to generate an oscillator signal having a frequency that varies based on a variation of the current, wherein the frequency of the oscillator signal varies the frequency from the initial frequency to the final frequency according to the initial current or the final current, respectively, wherein the current varying between the initial current and the final current increases in a substantially linear manner. [2] Oscillation circuit comprising: a crystal oscillator structure; and a boost circuit configured to induce oscillation in the crystal oscillator structure, wherein the boost circuit is configured to excite the crystal oscillator structure with an excitation signal having a frequency varying from an initial frequency to a final frequency, the initial frequency and the final frequency defining a frequency band, and wherein a resonance frequency of the crystal oscillator structure is located within the frequency band, wherein the boost circuit comprises: a current ramp circuit configured to generate a current that varies between an initial current and a final current; and an oscillator circuit coupled to the current ramp circuit and configured to generate an oscillator signal having a frequency that varies based on a variation of the current, wherein the frequency of the oscillator signal varies the frequency from the initial frequency to the final frequency according to the initial current or the final current, respectively, wherein the oscillator circuit comprises: a capacitance element connected between the current ramp circuit and a reference potential, the capacitance element being connected to the current ramp circuit at a first node; and a switch connected in parallel with the capacitance element; wherein the current from the current ramp circuit charges the capacitance element and causes a voltage in the capacitance element at the first node to increase in a generally linear manner and thereby resembles a triangular-type waveform at the capacitance element. [3] An oscillation circuit according to claim 1 or 2, wherein the initial frequency is greater than zero Hertz. [4] Oscillation circuit according to one of claims 1-3, wherein the current ramp circuit comprises: a ramp generator circuit configured to generate a voltage ramp signal that varies from an initial voltage to a final voltage; and a voltage-to-current converter circuit configured to convert the voltage ramp signal into a current ramp signal, the current ramp signal comprising the current varying between the initial current and the final current, the initial current and the final current corresponding to the initial voltage and the final voltage, respectively. [5] The oscillation circuit of claim 2, wherein the current ramp signal from the current ramp circuit increases in a substantially linear manner, wherein an increase in the current ramp signal causes an increase in a capacitance charging rate and thus causes an increase in a frequency of the excitation signal. [6] A method for inducing oscillation in a crystal oscillator structure, comprising: activating a boost circuit to generate a frequency output signal whose frequency varies from an initial frequency to a final frequency, thereby defining a frequency range; and Applying the frequency output signal to the crystal oscillator structure, wherein a resonance frequency of the crystal oscillator structure lies in the frequency range defined by the boost circuit, wherein the boost circuit comprises a current ramp circuit, and wherein activating the boost circuit comprises activating the current ramp circuit to generate a current ramp signal comprising a current varying between an initial current and a final current, wherein activating the boost circuit further comprises: Supplying the current ramp signal to an oscillator circuit; and Generating the frequency output signal based on the current ramp signal using the oscillator circuit, wherein generating the frequency output signal comprises: Charging a capacitance element using the current ramp signal; Discharging the capacitance element each time a voltage in the capacitance element reaches a threshold voltage during charging, wherein sustained charging and discharging of the capacitance element using the current ramp signal results in a generally triangular voltage waveform across the capacitance element having a frequency that varies between the initial current and the final current in a manner corresponding to the current ramp signal. [7] The method of claim 6, wherein the current ramp signal comprises a current that varies in a substantially linear manner between the initial current and the final current. [8] The method of claim 6, wherein generating the frequency output signal further comprises converting the generally triangular voltage waveform into a generally rectangular waveform having the frequency varying in a manner corresponding to the current ramp signal. [9] The method of any one of claims 6 to 8, wherein the current ramp circuit comprises a voltage ramp circuit and a voltage-to-current converter, and wherein activating the current ramp circuit to generate a current ramp signal comprises: activating the voltage ramp circuit to generate a voltage ramp signal; and Input the voltage ramp signal into the voltage-to-current converter to generate the current ramp signal. [10] The method of any one of claims 6 to 9, further comprising deactivating the boost circuit after applying the frequency output signal to the crystal oscillator structure. [11] Oscillation circuit comprising: a vibration system; and a boost circuit configured to induce oscillation in the oscillating system, wherein the boost circuit is configured to excite the oscillation system with an excitation signal having a frequency varying from an initial frequency to a final frequency, the initial frequency and the final frequency defining a frequency band, and where a resonance frequency of the oscillation system is located within the frequency band, wherein the boost circuit comprises: a ramp circuit configured to generate a quantity that varies between an initial quantity and a final quantity; and an oscillator circuit coupled to the ramp circuit and configured to generate an oscillator signal having a frequency that varies based on a variation of the quantity, wherein the frequency of the oscillator signal varies the frequency from the initial frequency to the final frequency according to the initial quantity or the final quantity, respectively, wherein the oscillator circuit comprises: a capacitance element connected between the ramp circuit and a reference potential, the capacitance element being connected to the ramp circuit at a first node; and a switch connected in parallel with the capacitance element; and wherein the current from the ramp circuit charges the capacitance element and causes a voltage in the capacitance element at the first node to increase in a generally linear manner and thereby resembles a triangular-type waveform. [12] The oscillation circuit of claim 11, wherein the oscillation system comprises a crystal oscillator structure, a MEMS oscillator, or an electromechanical oscillator. [13] An oscillating circuit according to claim 11, wherein the quantity is a current, a voltage or a digital word. [14] An oscillation circuit according to claim 11 or 13, wherein the quantity varying between the initial quantity and the final quantity varies in a substantially linear manner.

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