Oscillator circuit and current compensation circuit for oscillator

Abstract

A current compensation circuit includes a current generating circuit and a current generating circuit. A first node of the current generating circuit is coupled to an input signal. A second node of the current generating circuit is coupled to a process-dependent current. The current generating circuit provides a compensation current based on the input signal and the process-dependent current. A signal generator is used to couple a supply voltage to the first node to provide the input signal. The signal level of the input signal changes in response to variations in the supply voltage. A power supply node of an oscillator receives the supply current to drive the oscillator. The current generating circuit draws the compensation current from the power supply node to compensate for variations in the supply current caused by variations in the supply voltage.

Description

[Technical Field]

[0001] This disclosure relates to oscillating circuits, and more particularly to a current compensation circuit for an oscillator, and an oscillating circuit with high power supply fluctuation immunity. [Previous Technology]

[0002] A system-on-chip (SoC) is an integrated circuit (IC) that integrates the components of an entire electronic system onto a single platform. Power supplies drive numerous functional blocks tightly integrated on the same chip. SoCs can reduce designs that typically require multiple chips to a single processor, thereby reducing energy waste and saving space in large systems. However, the high operating frequency of SoCs causes power supplies to drive rapidly varying loads, generating noise in the power supply bus. This noise reduces the power supply rejection ratio (PSRR) and propagates within the chip, resulting in jitter, which reduces the dynamic range of sensitive functional blocks (such as phase-locked loops, PLLs). In SoC designs at advanced technology nodes, the degradation of PSRR is more severe due to the reduction in supply voltage. Therefore, there is a need in the art for an improvement to reduce the adverse effects of power supply variation. [Summary of the Invention]

[0003] The embodiments disclosed herein provide a current compensation circuit for an oscillator, and an oscillator circuit with high power supply variation immunity.

[0004] Certain embodiments of this disclosure include a current compensation circuit for an oscillator. The current compensation circuit includes a current generating circuit and a current generating circuit. The current generating circuit has a first node and a second node. The first node is coupled to an input signal. The second node is coupled to a process-dependent current. The current generating circuit provides a compensation current based on the input signal and the process-dependent current. A signal generator is coupled to the first node to couple a supply voltage to the first node to provide the input signal. The signal level of the input signal varies with changes in the supply voltage. The oscillator's power supply node receives a supply current to drive the oscillator. The current generating circuit draws the compensation current from the oscillator's power supply node to compensate for variations in the supply current caused by changes in the supply voltage.

[0005] Certain embodiments of this disclosure include an oscillation circuit. The oscillation circuit includes a current generator, an oscillator, and a current compensation circuit. The current generator is powered by a supply voltage to output a supply current. The oscillator has a power supply node for receiving the supply current. The oscillator generates an oscillation signal based on a drive current. A first portion of the supply current flows into the oscillator from its power supply node as the drive current. The current compensation circuit is coupled to the oscillator's power supply node and generates a first portion of a compensation current based on the supply voltage and a reference signal, and a second portion of the compensation current based on a first process-dependent current. The signal level of the reference signal is independent of variations in the supply voltage, and the first portion of the compensation current varies with these variations. The current compensation circuit draws the compensation current from the oscillator's power supply node to compensate for variations in the supply current caused by variations in the supply voltage.

[0006] The current compensation scheme provided in this disclosure enables the oscillation circuit to generate an oscillation signal with a stable (or approximately fixed) frequency under power supply fluctuations. The current compensation scheme provided in this disclosure improves the oscillation circuit's immunity to power supply noise. Furthermore, the oscillation circuit can be used to implement a phase-locked loop (PLL) with less jitter and phase noise. The current compensation scheme provided in this disclosure improves the power supply rejection ratio (PSRR) without increasing the voltage margin of the PLL.

[0007] The various embodiments disclosed herein can be clearly understood by reading the accompanying drawings. It should be noted that, according to standard practice in the art, the various features in the drawings are not necessarily drawn to scale. In fact, the size of certain features may be arbitrarily enlarged or reduced for clear description. FIG1 is a schematic diagram of an exemplary oscillating circuit according to some embodiments of the present disclosure. FIG2 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG3 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG4 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG5 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG6 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG7 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG8 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG9 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG10 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. FIG11 is an embodiment of the oscillating circuit shown in FIG1 according to some embodiments of the present disclosure. Figure 12 is an embodiment of the oscillation circuit shown in Figure 1 according to certain embodiments of the present disclosure.

Implementation Method

[0008] The following disclosure provides various embodiments or examples that can be used to implement different features of this disclosure. Specific examples of elements and configurations described below are used to simplify this disclosure. It is understood that these descriptions are merely illustrative and are not intended to limit the scope of this disclosure. For example, element symbols and / or reference numerals may be reused in multiple embodiments. Such reuse is for the purpose of brevity and clarity and does not in itself represent a relationship between the different embodiments and / or configurations discussed.

[0009] Furthermore, it is understood that if a component is described as being "connected to" or "coupled to" another component, then the two components may be directly connected or coupled, or there may be other intervening components between them.

[0010] To enhance the ability to suppress power supply ripple, phase-locked loops (PLLs) can utilize high-impedance paths to reduce fluctuations in the supply current injected into the current-controlled oscillator (DCO). For example, a cascode circuit consisting of two transistors connected in series can be provided between the power supply and the DCO to reduce ripple in the supply current. However, in some manufacturing processes, the transistors used in the cascode circuit exhibit relatively low output resistance. Connecting the cascode circuit between the power supply and the DCO is insufficient to provide good jitter performance.

[0011] One approach is to add a gain boosting stage at the output of the cascaded circuit, thereby increasing the output impedance as seen from the output of the cascaded circuit. However, one or more transistors in the gain boosting stage will be in series with the transistors in the cascaded circuit, resulting in an increased voltage headroom. This approach is not suitable for circuit designs at advanced technology nodes.

[0012] This disclosure provides exemplary current compensation circuits, each of which generates a compensation current by emulating / simulating the effects of process, voltage, and / or temperature variations on the supply current (which is injected into the oscillator's supply node). The current compensation circuit can draw compensation current from the supply node to compensate for variations in the supply current. For example, the compensation current may be sourced from the supply current and may be equivalent to a portion of the supply current that changes with process, voltage, and / or temperature variations. Another portion of the supply current that is unaffected (or almost unaffected) by process, voltage, and / or temperature variations can flow through the supply node into the oscillator as a drive current, which is used to control the oscillation frequency of the oscillator. Therefore, the oscillation frequency may be unaffected or almost unaffected by power supply variations.

[0013] This disclosure also provides an exemplary oscillator circuit with high power supply variability immunity. Each oscillator circuit can be applied in a phase-locked loop to reduce phase noise and jitter. Further explanation follows.

[0014] FIG1 is a schematic diagram of an exemplary oscillation circuit according to certain embodiments of the present disclosure. The oscillation circuit 100 can be used to implement a phase-locked loop with high power supply noise immunity. However, this is not intended to limit the scope of the present disclosure. Those skilled in the art will understand that the oscillation circuit 100 can be applied to other circuits or devices without departing from the scope of the present disclosure. Furthermore, the oscillator in the oscillation circuit 100 can be implemented as a current-controlled oscillator, wherein the oscillation frequency is controlled by a control current injected into the current-controlled oscillator. This example is for illustrative purposes and is not intended to limit the scope of the present disclosure. The current compensation scheme provided in the present disclosure can be applied to other types of oscillators (such as voltage-controlled oscillators or hybrid controlled oscillators) without departing from the scope of the present disclosure.

[0015] The oscillation circuit 100 may include (but is not limited to) a current generator 102, an oscillator 104, and a current compensation circuit 110. The current generator 102 is powered by a supply voltage VCC to output a supply current IS. The oscillator 104 may generate an oscillation signal CK OSC based on a control current injected into the oscillator 104. For example, the oscillator 104 has a supply node N OSC for receiving the supply current IS. The supply current IS may flow into the supply node N OSC to drive the oscillator 104. The drive current ID from the supply current IS may serve as the control current for the oscillator 104. For example, the frequency of the oscillation signal CK OSC may be controlled by the drive current ID.

[0016] The current compensation circuit 110 is coupled to the power supply node N OSC to draw current IC from the power supply node N OSC, thereby compensating for the effects of power supply noise on the supply current IS. For example, a change in the supply voltage VCC may cause a change in the supply current IS. The current IC can be a compensation current generated by simulating / analogizing the effects of power supply noise on the supply current IS. The drive current ID can be maintained at a constant or substantially constant level under power supply fluctuations. Therefore, the frequency of the oscillation signal CK OSC can be maintained at a constant or substantially constant level under power supply fluctuations.

[0017] For example (but not limited thereto), the current generator 102 may be implemented using a transistor MB biased by voltage VB, and the oscillator 104 may be implemented using a ring oscillator. The combination of oscillator 104 and current generator 102 can be considered as a voltage-controlled oscillator. In the example shown in Figure 1, oscillator 104 may comprise N inverters A1 to AN connected in series, where N is an integer greater than 1. Note that current generator 102 and / or oscillator 104 may be implemented using other circuit structures without departing from the scope of this disclosure.

[0018] When the supply voltage VCC rises due to power supply noise, the supply current IS also increases accordingly. The current compensation circuit 110 can generate a current IC (e.g., a compensation current) that reflects the effect of power supply noise on the supply current IS. The current IC can be a part of the supply current IS, flowing from the power supply node N OSC to the current compensation circuit 110. Another part of the supply current IS (the supply current IS flowing from the power supply node N OSC to the oscillator 104) can serve as the drive current ID. Note that the drive current ID is the result of subtracting the current IC from the supply current IS, and therefore can be kept at a constant or approximately constant level. By simulating / analogizing the effect of power supply noise on the supply current IS, the current compensation circuit 110 can reduce / eliminate the effect of power supply noise on the frequency stability of the oscillator 104.

[0019] In some embodiments, process and / or temperature variations in the current generator 102 and oscillator 104 may cause the supply current IS to respond differently to power supply noise. The current compensation circuit 110 may further mimic / simulate the effects of process and / or temperature variations to generate a current IC for noise compensation.

[0020] For example, consider a scenario where both the first and second circuits are implemented using the same structure comprised of a current generator 102 and an oscillator 104. When subjected to the same power supply noise or voltage fluctuations, the first and second circuits may exhibit different current responses due to process variations. Furthermore / or, the first / second circuits may exhibit different current responses when subjected to the same power supply noise or voltage fluctuations at different temperatures. In other words, the supply current fluctuations caused by power supply noise may differ due to process and / or temperature variations. The current compensation scheme provided in this disclosure can compensate for supply current fluctuations caused by process, voltage, and / or temperature variations.

[0021] FIG2 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. The current compensation circuit 110 includes (but is not limited to) a signal generator 120 and a current generation circuit 130. The signal generator 120 can be used to couple the supply voltage VCC to node NM1 of the current generation circuit 130 to provide an input signal SIN. The signal level of the input signal SIN can vary with the supply voltage VCC. That is, the input signal SIN can be related to voltage variations. In some examples, the input signal SIN can be a current signal that indicates the effect of variations in the supply voltage VCC on the supply current IS. In some examples, the input signal SIN can be a voltage signal that carries information about variations in the supply voltage VCC (or information about the noise components of the supply voltage VCC).

[0022] Nodes NM1 and NM2 of the current generation circuit 130 can be coupled to the input signal SIN and the process-dependent current IPT, respectively. The current generation circuit 130 can provide a compensation current (i.e., current IC) based on the input signal SIN and the process-dependent current IPT. Note that current IC can flow from the power supply node NOSC to compensate for variations in the supply current IS caused by process, voltage, and / or temperature variations.

[0023] The process-dependent current IPT can be related to process variations. For example, if the current compensation scheme provided in this disclosure is not applied to the oscillator 104, the supply current IS will vary in response to transistor process variations. To compensate for process variations, the current generation circuit 130 can provide a process-dependent current IPT by simulating / parameterizing the effect of process variations on the supply current IS. In some embodiments, the process-dependent current IPT may also be temperature-dependent. The process-dependent current IPT can be controlled to flow into or out of the current generation circuit 130 to compensate for process and temperature variations.

[0024] During operation, the supply current IS can be supplied to the power supply node N OSC to drive the oscillator 104. The signal generator 120 can provide an input signal S IN, which can vary in response to changes in the supply voltage VCC. A process-dependent current I PT, which is related to process and / or temperature variations, can flow through node N M2. The current generation circuit 130 can draw a current IC from the power supply node N OSC based on the input signal S IN and the process-dependent current I PT, thereby compensating for the variation in the supply current IS caused by changes in the supply voltage VCC. Note that the variation in the supply current IS caused by changes in the supply voltage VCC may vary due to changes in the process and / or temperature. By means of the current IC (which is related not only to the effect of power supply noise on the supply current IS, but also to the effect of changes in the process and / or temperature on the supply current IS), the current generation circuit 130 can compensate for the variation in the supply current IS caused by process, voltage, and / or temperature variations. Oscillator 104 can generate an oscillation signal CK OSC based on a drive current ID with a constant (or approximately constant) level.

[0025] By means of the current compensation scheme provided in this disclosure, the oscillation circuit can generate an oscillation signal with a stable frequency (or a substantially fixed frequency) under power supply fluctuations. The current compensation scheme provided in this disclosure can improve the oscillation circuit's immunity to power supply noise. In addition, the oscillation circuit can be used to implement a phase-locked loop that reduces jitter and phase noise.

[0026] To facilitate understanding of the contents of this disclosure, certain embodiments are given below to further illustrate the current compensation scheme provided by this disclosure. Those skilled in the art should understand that other embodiments employing the circuit structure shown in Figure 1 or Figure 2 fall within the scope of this disclosure.

[0027] FIG3 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. The oscillation circuit 300 may include a current generator 302, an oscillator 304, and a current compensation circuit 310. The current generator 302 and the oscillator 304 may be implemented as the current generator 102 and oscillator 104 shown in FIG1, respectively. Both the current generator 302 and the oscillator 304 can be represented by the current source symbol. In addition, the current compensation circuit 310 may be an embodiment of the current compensation circuit 110 shown in FIG2. The current compensation circuit 310 may include a signal generator 320 and a current generation circuit 330, which may be embodiments of the signal generator 120 and the current generation circuit 130 shown in FIG2, respectively.

[0028] In this embodiment, the input signal SIN shown in FIG2 can be an input current IIN flowing into node NM1. For example, current generation circuit 330 can be used to provide node voltage VN at node NM1. The voltage level of node voltage VN is independent (or nearly independent) of the variation of supply voltage VCC. Signal generator 320 has a power supply node NCG coupled to supply voltage VCC. Signal generator 320 can provide input current IIN based on the voltage difference between supply voltage VCC and node voltage VN. Input current IIN flows into node NM1 as an embodiment of the input signal SIN shown in FIG2.

[0029] The signal generator 320 can be implemented using a current source to provide the input current IIN. In the example shown in Figure 3, the signal generator 320 can be implemented using a resistive current source, which includes a resistive element R1 coupled between the power supply node NCG and the node NM1. The magnitude of the input current IIN can be equal to (or approximately equal to) the voltage difference between the supply voltage VCC and the node voltage VN divided by the resistance value of the resistive element R1.

[0030] The current generation circuit 330 may include (but is not limited to) a current mirror 332 and a current generator 336. The current mirror 332 is coupled to the signal generator 320 via node N M1 and has a node NC1 coupled to the power supply node N OSC. The current mirror 332 is used to provide a node voltage VN at node N M1, draw a first portion of the input current I IN from node N M1 (i.e., current I M1), and mirror a first portion of the input current I IN to provide current IC. Current IC can flow from node NC1 into the current mirror 332.

[0031] For example (but not limited thereto), the current mirror 332 may include an amplifier 334 and transistors M41 and M42. The amplifier 334 has an input terminal TI1, an input terminal TI2, and an output terminal TO. The input terminal TI1 is coupled to a reference voltage VREF. The input terminal TI2 is coupled to node NM1 to provide a node voltage VN at node NM1 based on the reference voltage VREF. The reference voltage VREF may be insensitive to process, voltage, and temperature (PVT) variations, or may be unaffected by PVT variations. For example, the reference voltage VREF may be provided by a bandgap voltage reference. Furthermore, the node voltage VN may be equal to (or approximately equal to) the reference voltage VREF. In the example shown in Figure 3, the amplifier 334 may be implemented using an operational amplifier with a fairly large (or nearly infinite) gain, thereby forming a virtual short circuit in which the voltages of the inverting and non-inverting terminals are equal to or approximately equal to each other.

[0032] The control terminals of transistors M41 and M42 are both coupled to the output terminal TO. The first connection terminal of transistor M41 is coupled to node NM1, and current IM1 flows into transistor M41 from the first connection terminal. The first connection terminal of transistor M42 is coupled to node NC1, and current IC flows into transistor M42 from the first connection terminal. Furthermore, the second connection terminals of both transistors M41 and M42 can be coupled to a reference voltage VSS, such as ground voltage.

[0033] Furthermore, the current generator 336 is coupled to the supply voltage VCC via node NM2 and has a node NC2 coupled to node NM1. The current generator 336 can draw a second portion (i.e., current IM2) of the input current IIN from node NM1 based on a process-dependent current IPT. The current generator 336 may include (but is not limited to) a current mirror 338 and a resistive element R2. The current mirror 338 can be used to mirror the process-dependent current IPT to draw current IM2 (i.e., the second portion of the input current IIN) from node NM2. Current IM2 can be considered as a process-dependent current.

[0034] Both process-dependent currents IPT and IM2 can be correlated with the effect of process variations on the supply current IS. For example (but not limited to this disclosure), the current generator 302 or oscillator 304 can be a MOS-based circuit, which is a circuit developed using a metal-oxide-semiconductor field-effect transistor (MOSFET). The process-dependent current IPT can flow through the transistor of the current mirror 338, and therefore can be correlated with the current response of the transistor to process variations. The current IM2 generated in response to the process-dependent current IPT can also be correlated with the current response of the transistor to process variations. Note that the transistor of the current mirror 338 can be temperature-dependent. The process-dependent currents IPT and IM2 can also be correlated with the current response of the transistor to temperature variations.

[0035] In the example shown in Figure 3, the current mirror 338 may include transistors M31 and M32. The first connection terminal of transistor M31 is coupled to the control terminal of transistor M31 to receive a process-dependent current IPT. The control terminal of transistor M32 is coupled to the control terminal of transistor M31. The first connection terminal of transistor M32 is coupled to node NC2 to receive current IM2. That is, the current IM2 flowing from node NM1 can flow into transistor M32 from the first connection terminal of transistor M32. Furthermore, the second connection terminals of both transistors M31 and M32 are coupled to a reference voltage VSS. Note that both transistors M31 and M32 can be implemented using an n-channel transistor. If the oscillator 304 (or current generator 302) is NMOS (n-channel metal-oxide-semiconductor field-effect transistor) dominant, then the current IM2 can be related to the effects of process variations in the oscillator 304 (or current generator 302).

[0036] One end of resistive element R2 is coupled to the supply voltage VCC via node N M2, and the other end of resistive element R2 is coupled to the first connection terminal of transistor M 31. A process-dependent current I PT flows through the transistor (e.g., transistor M 31) of current mirror 338 and resistive element R2. Note that the resistance value of resistive element R2 can vary with temperature. Controlling the process-dependent current I PT to flow to (or out of) resistive element R2 can achieve better temperature compensation. For example, resistive element R2 can reduce or prevent overcompensation due to temperature variations.

[0037] During operation, current generator 302 outputs a supply current IS to power supply node N OSC based on the supply voltage VCC. Signal generator 320 can provide an input current I IN, which varies with the supply voltage VCC. The input current I IN can be divided into different parts at node N M1, which has a constant or approximately constant voltage (i.e., node voltage VN).

[0038] For example, the voltage difference across resistive element R1 causes the input current IIN to flow into node NM1. The voltage difference across resistive element R2 causes a process-dependent current IPT to flow into node NM2. Since the process-dependent current IPT flows through resistive element R2 and transistor M31, the process-dependent current IPT can be process- and temperature-dependent. Current mirror 338 can guide the process-dependent current IPT to transistor M31 and mirror the process-dependent current IPT to provide current IM2, which is a part of the input current IIN and flows into transistor M32. Another part of the input current IIN flows into transistor M41 as current IM1, which can be related to the effects of PVT variations.

[0039] Furthermore, the current mirror 332 can mirror the current I M1 to provide the current IC (i.e., compensation current). The current IC can flow out from the power supply node N OSC to compensate for fluctuations in the supply current IS. The oscillator 304 can generate an oscillation signal CK OSC with a stable (or approximately fixed) frequency based on the drive current ID.

[0040] Please note that since the process-dependent current IPT can be correlated with the current response of the transistor to process variations, the oscillator circuit 300 can achieve a high power supply rejection ratio at different process corners. Furthermore, the oscillator circuit 300 can have a low temperature coefficient due to the temperature response of the process-dependent current IPT. For example, when the supply current IS increases in response to a rise in temperature, the process-dependent current IPT flowing through the resistive element R2 and the transistor M31 can decrease. The current IM2 can decrease as the process-dependent current IPT decreases, and the current IM1 can increase as the current IM2 decreases, resulting in an increase in the compensation current IC. Therefore, the drive current ID can be maintained at a constant (or approximately constant) level. In other words, the oscillator circuit 300 can have a low temperature coefficient.

[0041] The circuit structure shown in Figure 3 is for illustrative purposes and is not intended to limit the scope of this disclosure. In some embodiments, the node voltage VN may be provided by other circuitry or devices that can generate a voltage unaffected by variations in the supply voltage VCC. In some embodiments, the signal generator 320 may be implemented using other circuitry, each of which can output a current that varies with the supply voltage VCC. In some embodiments, other circuitry / devices capable of generating temperature-dependent current may be used instead of the resistive element R2.

[0042] FIG4 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. The oscillation circuit 400 may include the current generator 302 and oscillator 304 shown in FIG3, and may further include a current compensation circuit 410. Except for the current generator 436 included in the current generation circuit 430, the structure of the current compensation circuit 410 is similar to / the same as the structure of the current compensation circuit 310 shown in FIG3.

[0043] Current generator 436 may include current mirror 438, resistive element R3, and current mirror 338 as shown in FIG. 3. Current mirror 438 is coupled to current mirror 338 via node N M3. Current mirror 438 is coupled to node N M2 and can mirror a process-dependent current I PT to provide a relay current (i.e., current I M3) flowing through node N M3. Current mirror 338 is coupled to current mirror 438 via node N M3 to mirror current I M3 to draw current I M2 from node N M1. Note that current I M3 may be related to the effect of process variations on the supply current IS. For example, current generator 302 or oscillator 304 may be a metal-oxide-semiconductor-based circuit. The process-dependent current I PT can flow through the transistor of current mirror 438, so both the process-dependent current I PT and current I M3 may be related to the current response of the transistor to process variations.

[0044] In the example shown in Figure 4, the current mirror 438 may include transistors M33 and M34. The control terminals of each transistor M33 and M34 are coupled to the first connection terminal of transistor M33. The first connection terminals of each transistor M33 and M34 are coupled to the supply voltage VCC. The second connection terminals of each transistor M33 and M34 are coupled to the resistive element R3 and node NM3, respectively. Note that both transistors M33 and M34 can be implemented as p-channel transistors. If the oscillator 304 (or current generator 302) is PMOS (p-channel metal-oxide-semiconductor field-effect transistor) dominant, then the process-dependent current IPT can be related to the effects of process variations in the oscillator 304 (or current generator 302).

[0045] One end of resistive element R3 is coupled to the second connection terminal of transistor M33, and the other end of resistive element R3 is coupled to the reference voltage VSS. A process-dependent current IPT flows through the transistor (e.g., transistor M33) of current mirror 438 and resistive element R3. Note that the resistance of resistive element R3 can vary with temperature. Controlling the process-dependent current IPT to flow into (or out of) resistive element R3 can achieve better temperature compensation. For example, resistive element R3 can reduce or prevent overcompensation due to temperature variations.

[0046] Since those skilled in the art should be able to understand the operational details of the oscillation circuit 400 shown in Figure 4 after reading the above description of Figures 1 to 3, further explanation will not be repeated here.

[0047] FIG5 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. The oscillation circuit 500 may include the current generator 302 and oscillator 304 shown in FIG3, and may further include a current compensation circuit 510. Except for the current generator 536 included in the current generating circuit 530, the structure of the oscillation circuit 500 is similar to / the same as the structure of the oscillation circuit 300 shown in FIG3.

[0048] In this embodiment, the control terminal and the first connection terminal of transistor M31 are both coupled to the supply voltage VCC. Current mirror 338 can mirror a process-dependent current IPT to provide current IM2. Through current compensation circuit 510, oscillation circuit 500 can achieve a high power supply rejection ratio at different process angles. Since those skilled in the art should understand the operational details of the oscillation circuit 500 shown in FIG5 after reading the above description of FIG1 to FIG4, further explanation is not required here.

[0049] FIG6 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. The oscillation circuit 600 may include the current generator 302 and oscillator 304 shown in FIG3, and may further include a current compensation circuit 610. Except for the current generator 636 included in the current generation circuit 630, the structure of the oscillation circuit 600 is similar to / the same as the structure of the oscillation circuit 400 shown in FIG4.

[0050] In this embodiment, the second connection terminal of transistor M33 is coupled to a reference voltage VSS. Current mirror 438 can mirror a process-dependent current IPT to provide current IM3. With the current compensation circuit 610, the oscillation circuit 600 can achieve a high power supply rejection ratio at different process angles. Since those skilled in the art should understand the operational details of the oscillation circuit 600 shown in FIG6 after reading the above description of FIG1 to FIG5, further explanation is not required here.

[0051] FIG7 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. Except for the current compensation circuit 710, the structure of the oscillation circuit 700 is similar to / identical to the structure of the oscillation circuit 300 shown in FIG3. In this embodiment, the input current IIN injected into node N M1 can be used as the current IM1 input to transistor M 41. With the current compensation circuit 710, the oscillation circuit 700 can achieve a high power supply rejection ratio. Since those skilled in the art should understand the operational details of the oscillation circuit 700 shown in FIG7 after reading the above description of FIG1 to FIG6, further description will not be repeated here.

[0052] FIG8 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. Except for the current compensation circuit 810, the structure of the oscillation circuit 800 is similar to / identical to the structure of the oscillation circuit 300 shown in FIG3. In this embodiment, the input signal SIN shown in FIG2 can be a voltage signal applied to node NM1. For example, the signal generator 820 can provide the input voltage VIN by capacitively coupling the supply voltage VCC to node NM1. The input voltage VIN can be an embodiment of the input signal SIN shown in FIG2.

[0053] The signal generator 820 can be implemented using a voltage source (which provides the input voltage VIN). In the example shown in Figure 8, the signal generator 820 may include a capacitive element C1, which can serve as a voltage source coupled between the power supply node NCG and node NM1. The input voltage VIN may carry information about the variation of the supply voltage VCC (or the alternating current (AC) component of the supply voltage VCC).

[0054] The current generating circuit 830 may include (but is not limited to) a current source 834, a transistor M81, and a transistor M82. In this embodiment, the current source 834 may be associated with the current generator 302. For example, the current source 834 may be coupled to the supply voltage VCC via node NM2 and used to provide a process-dependent current IPT, which may be related to the effect of process variations on the supply current IS.

[0055] Furthermore, the connection terminal of transistor M81 is coupled to the control terminal of transistor M81, and is also coupled to current source 834 to receive process-dependent current IPT. The connection terminal of transistor M82 is coupled to node NC1. The control terminal of transistor M82 is coupled to node NM1 and electrically connected to the control terminal of transistor M81. In the example shown in FIG8, the control terminal of transistor M82 can be electrically connected to the control terminal of transistor M81 via resistive element R4.

[0056] In operation, the current generation circuit 830 can act as a current mirror to mirror a process-dependent current IPT to provide a first portion (denoted as current ICP) of the compensation current IC. A first component (e.g., a direct current (DC) component) of the node voltage VN can be established at node NM1 in response to the process-dependent current IPT. Furthermore, the power supply noise or voltage ripple presented by the supply voltage VCC can be capacitively coupled to node NM1 to generate an input voltage VIN, which can serve as a second component (e.g., an AC component) of the node voltage VN. A second portion (denoted as current ICV) of the current IC can flow into transistor M82 in response to the second component of the node voltage VN. Therefore, the current IC can be correlated with the effects of PVT variations. The current compensation circuit 810 can draw current IC from the power supply node NOSC to compensate for variations in the supply current IS. The oscillator 304 can generate an oscillation signal CKOSC with a stable (or approximately fixed) frequency based on the drive current ID.

[0057] The oscillation circuit 800 can achieve a high power supply rejection ratio at different process angles by means of the current compensation circuit 810. Note that the circuit structure shown in Figure 8 is for illustrative purposes and is not intended to limit the scope of this disclosure. In some embodiments, the first component of the node voltage VN may be generated by other circuitry (which can provide a process-dependent current IPT). In some embodiments, the resistive element R4 may be omitted.

[0058] FIG9 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. Except for the current generating circuit 930, the structure of the oscillation circuit 900 is similar / identical to the structure of the oscillation circuit 800 shown in FIG8. In this embodiment, the current generating circuit 930 includes (but is not limited to) a current mirror 932 and a current generator 336 shown in FIG3. The current mirror 932 may include the resistive element R4 shown in FIG8 and transistors M81 and M82, and a current source 934 for providing a reference current IREF. The current level of the reference current IREF may be unaffected by variations in the supply voltage VCC, or may be insensitive to variations in the supply voltage VCC.

[0059] The current mirror 932 can be used to mirror a first portion of the reference current IREF (i.e., current IP1) to provide a first portion of the compensation current IC (represented by current IC1). Current IP1 can be related to process and / or temperature variations. For example, current generator 336 is coupled to the current mirror 932 via node NC2 and is used to draw a second portion of the reference current IREF (i.e., current IP2) from node NC2 based on a process-dependent current IPT. Both the process-dependent current IPT and current IP2 can be related to process and / or temperature variations. Therefore, current IP1 (i.e., the result of subtracting current IP2 from the reference current IREF) can be related to process and / or temperature variations.

[0060] In operation, current mirror 932 mirrors current I P1 to provide a first portion of the compensation current IC (i.e., current IC1 related to process and / or temperature variations). Supply noise or voltage ripple presented by the supply voltage VCC can be capacitively coupled to node N M1, thereby generating a second portion of the compensation current IC (represented by current IC2), which flows into transistor M 82. Current IC2 is related to voltage variations. Therefore, the current IC flowing into node N C1 can be related to the effects of PVT variations. Current compensation circuit 910 can draw current IC from supply node N OSC to compensate for variations in the supply current IS. Oscillator 304 can generate an oscillation signal CK OSC with a stable (or approximately fixed) frequency based on the drive current ID.

[0061] Through the current compensation circuit 910, the oscillation circuit 800 can achieve a high power supply rejection ratio and a low temperature coefficient at different process angles. Since those skilled in the art should be able to understand the operational details of the oscillation circuit 900 shown in Figure 9 after reading the above description of Figures 1 to 8, further explanation will not be repeated here.

[0062] FIG10 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. Except that the current compensation circuit 1010 utilizes the current generator 436 shown in FIG4 to compensate for process and temperature variations, the structure of the oscillation circuit 1000 is similar / identical to the structure of the oscillation circuit 900 shown in FIG9. In this embodiment, the current generation circuit 1030 in the current compensation circuit 1010 includes the current mirror 932 shown in FIG9 and the current generator 436 shown in FIG4. In some embodiments, the resistive element R3 may be omitted. Since those skilled in the art should understand the operational details of the oscillation circuit 1000 shown in FIG10 after reading the above description of FIG1 to FIG9, further details will not be repeated here.

[0063] FIG11 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. Except for the current compensation circuit 1110, the structure of the oscillation circuit 1100 is similar to / identical to the structure of the oscillation circuit 900 shown in FIG9. In this embodiment, the current compensation circuit 1110 includes a current generating circuit 1130 and a signal generator 820 shown in FIG8.

[0064] The current generating circuit 1130 includes (but is not limited to) a current generator 1136 and a current mirror 932 as shown in FIG. 9. In the example shown in FIG. 11, the current generator 1136 includes a current mirror 438 as shown in FIG. 4 and a resistive element R3. The current mirror 438 is coupled to node NC2 and is used to mirror a process-dependent current IPT to provide a current IP3 flowing into node NC2. The current IP3 may be related to the effect of process and / or temperature variations on the supply current IS. The current mirror 932 may provide a first portion of the compensation current IC (which is related to process and / or temperature variations) by mirroring the current IP4 (i.e., the sum of the reference current IREF and the current IP3). The current mirror 932 may also provide a second portion of the compensation current IC in response to power supply noise capacitively coupled to node NM1. Therefore, the current IC flowing into node NC1 may be related to the effect of PVT variations.

[0065] Through the current compensation circuit 1110, the oscillation circuit 1000 can achieve a high power supply rejection ratio and a low temperature coefficient at different process angles. Since those skilled in the art should understand the operational details of the oscillation circuit 1100 shown in Figure 11 after reading the above description of Figures 1 to 10, further explanation will not be repeated here.

[0066] FIG12 is an embodiment of the oscillation circuit 100 shown in FIG1 according to certain embodiments of the present disclosure. Except for the current generating circuit 1230, the structure of the oscillation circuit 1200 is similar / identical to the structure of the oscillation circuit 800 shown in FIG8. In this embodiment, node N M2 of the current generating circuit 1230 is coupled to the power supply node N OSC to determine the current IC. The current generating circuit 1230 may include (but is not limited to) a transistor M 121 and a resistive element R5. The control terminal of the transistor M 121 is coupled to node N M1, the first connection terminal of the transistor M 121 is coupled to the power supply node N OSC via node N M2, and the second connection terminal of the transistor M 121 is coupled to the reference voltage VSS. The resistive element R5 is used to couple the first connection terminal of the transistor M 121 to the control terminal of the transistor M 121.

[0067] During operation, when the supply voltage VCC is at a constant level, the resistive element R5 coupled between the first connection terminal and the control terminal of transistor M121 enables / causes a process-dependent current IPT to flow into transistor M121 via node NM2. The process-dependent current IPT can be related to the effect of process variations on the supply current IS. Furthermore, when supply voltage VCC experiences power supply noise (or voltage ripple), signal generator 820 can capacitively couple the power supply noise (or voltage ripple) to node NM1, thereby generating an input voltage VIN, and current compensation circuit 1210 can draw current IC from power supply node NOSC to compensate for variations in the supply current IS. Oscillator 304 can generate an oscillation signal CKOSC with a stable (or approximately fixed) frequency based on the drive current ID. In the example shown in Figure 12, the current IC includes process-dependent currents IPT and IP0, where current IP0 flows into node NM2 of transistor M121 in response to input voltage VIN.

[0068] Please note that at least a portion of the compensation current provided by the disclosed current compensation scheme can be generated based on the supply voltage and a reference signal. At least a portion of the compensation current can correspond to the effect of power supply noise or voltage fluctuations on the supply current. The signal level of the reference signal is independent of the supply voltage fluctuations.

[0069] Referring again to Figure 2, the current compensation circuit 110 can be configured to generate at least a portion of the current IC based on the supply voltage VCC and the reference signal SREF. The signal level of the reference signal SREF is independent of the variation in the supply voltage VCC, and at least a portion of the current IC varies in response to the variation in the supply voltage VCC. For example (but not limited thereto), the reference signal SREF can be a reference voltage unaffected by the variation in the supply voltage VCC. In another example, the reference signal SREF can be a reference current unaffected by the variation in the supply voltage VCC. Furthermore, the current compensation circuit 110 can be configured to generate another portion of the current IC based on a process-dependent current (e.g., a process-dependent current IPT).

[0070] For example, referring again to Figure 3, the reference signal SREF shown in Figure 2 can be implemented using the node voltage VN coupled to node NC2. Signal generator 320 and current mirror 332 can be part of current generator 316. Current generator 316 can be configured to generate an input current IIN based on the supply voltage VCC and the node voltage VN, and draw current IC from the power supply node NOSC based on the input current IIN and a process-dependent current (i.e., current IM2) applied to node MN1. Furthermore, current generator 336 is used to generate a process-dependent current IPT and provide current IM2 based on the process-dependent current IPT. The combination of input current IIN and current IM2 (e.g., input current IIN minus current IM2) can serve as a compensation current generated by current compensation circuit 310. Current compensation circuit 310 can draw compensation current (i.e., current IC) from the power supply node NOSC based on the combination of input current IIN and current IM2.

[0071] Referring again to Figure 8, in another example, the reference signal SREF shown in Figure 2 can be implemented by a reference voltage VSS, wherein the voltage level of the reference voltage VSS is unaffected by variations in the supply voltage VCC. The capacitive element C1 and transistor M82 can be part of a current generator 816. The current generator 816 can be used to generate an input current (i.e., current ICV) based on the supply voltage VCC and the reference voltage VSS, and draw current IC from the supply node NOSC based on this input current and a first component (e.g., a DC component) of the node voltage VN at node NM1. Alternatively, the resistive element R4, current source 834, and transistor M81 can be part of a current generator 836. The current generator 836 can be used to generate a process-dependent current IPT and provide a first component (e.g., a DC component) of the node voltage VN based on the process-dependent current IPT. The combination of current ICP (i.e., a portion of the current IC flowing into transistor M82 in response to the first component (such as the DC component) of node voltage VN) and current ICV (i.e., a portion of the current IC flowing into transistor M82 in response to the second component (such as the AC component) of node voltage VN) can serve as the compensation current (i.e., current IC) provided by current compensation circuit 810.

[0072] Referring again to Figure 9, in another example, the reference signal S REF shown in Figure 2 can be implemented using a reference voltage VSS. The signal generator 820 and the current mirror 932 can be part of a current generator 916. The current generator 916 can generate a current IC1 based on the result of subtracting the current I P2 (i.e., the process-dependent current) from the reference current I REF. The current generator 916 can also generate a current IC2 based on the supply voltage VCC and the node voltage VN.

[0073] The circuit structures described above are for illustrative purposes and are not intended to limit the scope of this disclosure. For example, in some embodiments, the current compensation circuit 110 shown in FIG2 may be implemented to include a first current generator and a second current generator. The first current generator may generate an input current (e.g., the input current IIN shown in FIG3 or the current ICV shown in FIG8) based on the supply voltage VCC and the reference signal SREF (e.g., the node voltage VN shown in FIG3 or the reference voltage VSS shown in FIG8), and may draw current IC from the power supply node NOSC based on the input current and the electrical signal applied to node NM1 (e.g., the current IM2 shown in FIG3, or the DC component of the node voltage VN shown in FIG8). The first current generator and / or the second current generator may be implemented using other circuit structures without departing from the scope of this disclosure.

[0074] Furthermore, referring again to FIG12, the reference signal SREF shown in FIG2 can be implemented using a reference voltage VSS (which has a voltage level unaffected by variations in the supply voltage VCC). A capacitive element C1 is used to couple the supply voltage VCC to the control terminal of transistor M121, enabling / causing the first portion of the compensation current IC (i.e., current IP0) ​​to flow into transistor M121. A resistive element R5 is used to couple the first connection terminal of transistor M121 to the control terminal of transistor M121, enabling / causing the second portion of the compensation current IC (i.e., process-dependent current PT) to flow into transistor M121.

[0075] Since those skilled in the art should be able to understand the operational details of the current compensation circuit configured to generate a first part of compensation current based on the supply voltage and reference signal and a second part of compensation current based on process-dependent current after reading the above description of Figures 1 to 12, further explanation will not be repeated here.

[0076] The current compensation scheme provided in this disclosure enables the oscillation circuit to generate an oscillation signal with a stable (or approximately fixed) frequency under power supply fluctuations. The current compensation scheme provided in this disclosure improves the oscillation circuit's immunity to power supply noise. Furthermore, the oscillation circuit can be used to implement a phase-locked loop (PLL) with less jitter and phase noise. The current compensation scheme provided in this disclosure improves the power supply rejection ratio (PSRR) without increasing the voltage margin of the PLL.

[0077] The term "approximately" as used in this disclosure is used to describe and indicate minor variations. When these terms are used in conjunction with an event or situation, they can cover examples of an event or situation occurring precisely and examples of an event or situation being very close to occurring. For example, when the term "approximately" is used with a given value or range, it generally means ±10%, ±5%, ±1%, or ±0.5% of that given value or range. In this disclosure, a numerical range is expressed as from one endpoint to another or between two endpoints. Unless otherwise stated, the numerical ranges described in this disclosure may include endpoints. Furthermore, when multiple values ​​or characteristics are mentioned as "approximately" the same, it can cover situations where these values ​​are all within ±10%, ±5%, ±1%, or ±0.5% of the average of these values.

[0078] The foregoing description briefly outlines the features of certain embodiments of this disclosure, enabling those skilled in the art to gain a more comprehensive understanding of the various forms of this disclosure. Those skilled in the art will understand that they can readily use this disclosure as a basis to design or modify other processes and structures to achieve the same objectives and / or advantages as the embodiments described herein. Those skilled in the art should understand that these equivalent embodiments remain within the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure.

Claims

1. A current compensation circuit for an oscillator, comprising: a current generating circuit having a first node and a second node different from the first node, the current generating circuit being configured to receive an input signal via the first node, receive a process-dependent current via the second node, and provide a compensation current based on the input signal and the process-dependent current; and a signal generator coupled to the first node for coupling a supply voltage to the first node to provide the input signal, wherein the signal level of the input signal varies with changes in the supply voltage, and the input signal is transmitted from the signal generator to the current generating circuit via the first node; wherein a power supply node of the oscillator is configured to receive a supply current to drive the oscillator, and the current generating circuit is configured to draw the compensation current from the power supply node of the oscillator to compensate for changes in the supply current caused by changes in the supply voltage.

2. The current compensation circuit as claimed in claim 1, wherein the current generating circuit is used to provide a node voltage at the first node, the node voltage being independent of variations in the supply voltage; the signal generator is used to provide an input current based on the voltage difference between the supply voltage and the node voltage, and the input current flows into the first node as the input signal.

3. The current compensation circuit as claimed in claim 2, wherein the power supply node of the signal generator is coupled to the supply voltage; the signal generator includes a resistive element coupled between the first node and the power supply node of the signal generator.

4. The current compensation circuit as claimed in claim 2, wherein the current generating circuit comprises: a first current mirror coupled to the first node and the power supply node of the oscillator for providing the node voltage at the first node, drawing a first portion of the input current from the first node, and mirroring the first portion of the input current to provide the compensation current; and a current generator coupled to the first node and the second node for drawing a second portion of the input current from the first node based on the process-dependent current.

5. The current compensation circuit as claimed in claim 4, wherein the first current mirror comprises: an amplifier, wherein a first input terminal of the amplifier is coupled to a reference voltage; and a second input terminal of the amplifier is coupled to the first node and is used to provide a node voltage at the first node according to the reference voltage; A first transistor, wherein the control terminal of the first transistor is coupled to the output terminal of the amplifier, the connection terminal of the first transistor is coupled to the first node, and a first portion of the input current flows into the first transistor from the connection terminal of the first transistor; And a second transistor, wherein the control terminal of the second transistor is coupled to the output terminal of the amplifier, the connection terminal of the second transistor is coupled to the power supply node of the oscillator, and the compensation current flows into the second transistor from the connection terminal of the second transistor.

6. The current compensation circuit as described in claim 5, wherein the node voltage is equal to the reference voltage.

7. The current compensation circuit as claimed in claim 4, wherein the current generator includes: a second current mirror for mirroring the process-dependent current to draw a second portion of the input current from the first node, wherein the process-dependent current flows through a transistor of the second current mirror.

8. The current compensation circuit as claimed in claim 7, wherein the current generator further includes a resistive element coupled to the transistor, and the process-dependent current flows through the transistor and the resistive element.

9. The current compensation circuit as claimed in claim 4, wherein the current generator comprises: a second current mirror for mirroring a relay current to draw a second portion of the input current from the first node; a third current mirror coupled to the second current mirror for mirroring the process-dependent current to provide the relay current; and a resistive element coupled to the third current mirror, wherein the process-dependent current flows through a transistor of the third current mirror and the resistive element.

10. The current compensation circuit as claimed in claim 1, wherein the signal generator is configured to capacitively couple the supply voltage to the first node to provide an input voltage at the first node; the input voltage serves as the input signal.

11. The current compensation circuit as claimed in claim 10, wherein the current generating circuit includes: a current source coupled to the second node for providing the process-dependent current; A first transistor, wherein the connection terminal of the first transistor is coupled to the control terminal of the first transistor and coupled to the current source to receive the process-dependent current; And a second transistor, wherein the connection terminal of the second transistor is coupled to the power supply node of the oscillator, and the control terminal of the second transistor is coupled to the first node and electrically connected to the control terminal of the first transistor.

12. The current compensation circuit as claimed in claim 10, wherein the current generating circuit comprises: a current source for providing a reference current, wherein the current level of the reference current is independent of variations in the supply voltage; a first transistor, wherein a connection terminal of the first transistor is coupled to a control terminal of the first transistor and coupled to the current source to receive a first portion of the reference current; A second transistor, wherein the connection terminal of the second transistor is coupled to the power supply node of the oscillator to receive the compensation current, and the control terminal of the second transistor is coupled to the first node and electrically connected to the control terminal of the first transistor; And a current generator, coupled to the second node, for drawing a second portion of the reference current from the current source based on the process-dependent current.

13. The current compensation circuit as claimed in claim 10, wherein the second node is coupled to the power supply node of the oscillator to determine the compensation current, and the current generation circuit comprises: a transistor, wherein a control terminal of the transistor is coupled to the first node, a first connection terminal of the transistor is coupled to the power supply node of the oscillator via the second node, and a second connection terminal of the transistor is coupled to a reference voltage; a first portion of the compensation current flows through the second node due to the input voltage provided by the signal generator; and a resistive element for coupling the first connection terminal to the second connection terminal, such that a second portion of the compensation current flows through the second node, wherein the second portion of the compensation current is the process-dependent current.

14. An oscillation circuit comprising: a current generator powered by a supply voltage to output a supply current; an oscillator having a power supply node for receiving the supply current, the oscillator being configured to generate an oscillation signal based on a drive current, wherein a first portion of the supply current flows into the oscillator from the power supply node of the oscillator as the drive current; and a current compensation circuit coupled to the power supply node of the oscillator for generating a first portion of a compensation current based on the supply voltage and a reference signal, and generating a second portion of the compensation current based on a first process-dependent current, wherein the signal level of the reference signal is independent of variations in the supply voltage, and the first portion of the compensation current varies due to variations in the supply voltage; the current compensation circuit drawing the compensation current from the power supply node of the oscillator to compensate for variations in the supply current caused by variations in the supply voltage; both the first portion and the second portion of the compensation current flow into the current compensation circuit from the power supply node of the oscillator.

15. The oscillation circuit as claimed in claim 14, wherein the current compensation circuit comprises: a first current generator coupled to a power supply node of the oscillator and having a first node, the first current generator being configured to generate an input current based on the supply voltage and the reference signal, and to draw the compensation current from the power supply node of the oscillator based on the input current and an electrical signal applied to the first node; and a second current generator coupled to the first node being configured to generate the first process-dependent current, and to provide the electrical signal to the first node based on the first process-dependent current.

16. The oscillating circuit as claimed in claim 15, wherein the electrical signal provided by the second current generator is a second process-dependent current, and the first current generator comprises: a current mirror coupled to the first node and the power supply node of the oscillator for providing a node voltage at the first node, drawing a first portion of the input current from the first node, and mirroring the first portion of the input current to provide the compensation current, wherein the node voltage of the first node serves as the reference signal, and the voltage level of the node voltage is independent of variations in the supply voltage; and a current source coupled to the first node and having a power supply node coupled to the supply voltage, the current source being used to provide the input current based on the voltage difference between the supply voltage and the node voltage.

17. The oscillating circuit as claimed in claim 16, wherein the second current generator comprises: a current mirror for mirroring the first process-dependent current to provide the second process-dependent current, wherein the first process-dependent current flows through a transistor of the current mirror.

18. The oscillating circuit as claimed in claim 15, wherein the reference signal is a reference voltage whose voltage level is independent of variations in the supply voltage; the electrical signal provided by the second current generator is a first component of a node voltage of the first node; the first current generator includes: a capacitive element for capacitively coupling the supply voltage to the first node to provide a second component of the node voltage at the first node; and a first transistor, wherein a first connection terminal of the first transistor is coupled to a power supply node of the oscillator to receive the compensation current, a control terminal of the first transistor is coupled to the first node, and a second connection terminal of the first transistor is coupled to the reference voltage; wherein a first portion of the compensation current flows into the first transistor due to the first component of the node voltage; and a second portion of the compensation current flows into the first transistor due to the second component of the node voltage as the input current.

19. The oscillating circuit as claimed in claim 18, wherein the second current generator comprises: a resistive element, wherein a first terminal of the resistive element is coupled to the first node; and a current source for providing the first process-dependent current; And a second transistor, wherein the connection terminal of the second transistor is coupled to the current source to receive the first process-dependent current; The control terminal of the second transistor is coupled to the connection terminal of the second transistor and to the second terminal of the resistive element to provide the first component of the node voltage to the first node.

20. The oscillation circuit as claimed in claim 15, wherein the reference signal is a reference voltage whose voltage level is independent of variations in the supply voltage; the current compensation circuit comprises: a transistor, wherein a first connection of the transistor is coupled to a power supply node of the oscillator, and a second connection of the transistor is coupled to the reference voltage; a capacitive element for coupling the supply voltage to a control terminal of the transistor, such that a first portion of the compensation current flows into the transistor; and a resistive element for coupling the first connection to the control terminal, such that a second portion of the compensation current flows into the transistor, wherein the second portion of the compensation current serves as the first process-dependent current.

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