Voltage-controlled oscillator circuit

Abstract

Embodiments herein disclose an inductor-capacitor voltage controlled oscillator (LC-VCO) circuit. The LC-VCO circuit includes: an LC tank circuit including a center tap inductor connected in parallel with a capacitor bank without a varactor, where the LC tank circuit resonates to generate an oscillation voltage; and a control circuit connected to a varistor capacitance circuit, where the varistor capacitance circuit includes a varistor based on a voltage controlled transistor in series with at least one capacitor, the varistor capacitance circuit is connected in parallel with the LC tank circuit and connected to a negative transconductance circuit. The control circuit includes an error amplifier and a conversion circuit, and is configured to generate an output control voltage based on an input phase-locked loop (PLL) control voltage that controls a capacitance value of the varistor capacitance circuit through the variable resistor.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to semiconductor integrated circuits, and more specifically, to voltage-controlled oscillator (VCO) circuits. Background Technology

[0002] Typically, inductor-capacitor voltage-controlled oscillators (LC-VCOs) have a high quality factor that produces good phase noise. However, good phase noise also results in a narrow frequency range. To increase the frequency range of LC-VCOs, existing solutions use multiple VCOs, which requires additional area and power.

[0003] Conventional LC-VCOs include a varactor diode. The varactor diode has a monotonic, continuous voltage-capacitance dependence and can be located in a negative feedback continuous-time loop (such as a phase-locked loop (PLL)). However, the controllable range of the capacitance is less than 50% of the total value of the varactor diode. The frequency range of an LC-VCO depends on the ratio of the controllable tank capacitance to the total tank capacitance, and is therefore primarily limited by the varactor diode. Therefore, it is desirable to provide a wide frequency range in an LC-VCO while maintaining competitive area and power compared to conventional designs.

[0004] In the prior art, transformers are designed as adjustable inductors with strict phase matching constraints to replace varactor diodes; however, transformers occupy a large area in LC-VCOs.

[0005] Figure 1 A conventional LC-VCO 100 according to the prior art is shown. The LC-VCO 100 includes an LC tank circuit 107, which includes a center-tapped inductor 103 connected in parallel with a capacitor bank 102. Transistors M1 and M2 form a negative-gm (transconductance) circuit 104 to compensate for losses in the LC tank circuit. The capacitor bank 102 has capacitors digitally controlled for initial frequency calibration. C1 and C2 refer to MOS varactor diodes (connected to the drains of M1 and M2 via capacitors C3 and C4, respectively), and are controlled by a voltage... Controlled by a phase-locked loop (PLL). The voltage regulator generates the supply voltage for the LC-VCO. The MOS varactor diodes C1 and C2 are voltage-controlled variable capacitors. The frequency range of an LC-VCO depends on the ratio of the controllable tank capacitance to the total tank capacitance, and is primarily limited by the varactor diodes. For example, in a varactor diode with a total capacitance of 50 fF, the controllable component is only 24 fF. In other words, instead of a variable capacitor varying from 0 to 50 fF, an additional 25 fF component is unusable. A disadvantage of this varactor diode is that less than 50% of the total capacitance is controllable.

[0006] Therefore, there is a need in this field for solutions that can overcome the aforementioned drawbacks. Summary of the Invention

[0007] The main objective of the embodiments described herein is to disclose an inductor-capacitor voltage-controlled oscillator (LC-VCO).

[0008] Another objective of the embodiments described herein is to increase the frequency range of an LC-VCO by replacing the varactor diode with an identical functional element having a higher ratio of controllable capacitance to total capacitance.

[0009] Another objective of the embodiments herein is to disclose a voltage-controlled oscillator circuit with a negative feedback continuous-time loop.

[0010] Another objective of the embodiments described herein is to map the phase-locked loop control voltage to the capacitance value of the rheostat capacitor block in the voltage-controlled oscillator circuit.

[0011] By replacing traditional varactor diodes with similar or identical functional components that have a higher ratio of controllable capacitance to total capacitance, the LC-VCO embodiments described herein can achieve an increased frequency range. Furthermore, the VCO circuit embodiments can have a negative feedback continuous-time loop. The phase-locked loop control voltage can be mapped to the capacitance value of the varactor diode capacitor block in the VCO circuit.

[0012] In one embodiment, a voltage-controlled oscillator (VCO) circuit includes an inductor-capacitor (LC) tank circuit, the LC tank circuit including a center-tapped inductor connected in parallel with a capacitor bank without a varactor diode. The LC tank circuit resonates to generate an oscillating voltage at a specific frequency. The VCO circuit includes control circuitry connected to a varistor-capacitor circuit. The varistor-capacitor circuit includes a voltage-controlled transistor-based variable resistor connected in series with at least one capacitor, the varistor-capacitor circuit being connected in parallel with the LC tank circuit and connected to a negative transconductance circuit. The control circuitry includes an error amplifier and a conversion circuitry, and is configured to generate an output control voltage based on an input PLL control voltage, wherein the output control voltage controls the capacitance value of the varistor-capacitor circuit via the variable resistor.

[0013] This embodiment provides a method for controlling a voltage-controlled oscillator (VCO) circuit. The method includes: generating an equivalent voltage corresponding to a varistor capacitor from a switching current using a voltage generation circuit of a control circuit. The method further includes: mapping a phase-locked loop (PLL) control voltage to the capacitance of the varistor capacitor circuit via a voltage-controlled transistor in the varistor capacitor circuit using the control circuit, which includes an error amplifier. The control circuit forces the value of the equivalent voltage to be equal to the value of the PLL control voltage. The equivalent voltage is used to map the PLL control voltage to the capacitance value of the varistor capacitor circuit. Attached Figure Description

[0014] Embodiments of the invention are illustrated in the accompanying drawings, throughout which the same reference numerals indicate corresponding portions in the various figures. The embodiments of the invention will be better understood by referring to the following description with reference to the accompanying drawings shown below. Embodiments of the invention are illustrated by way of example in the accompanying drawings, wherein: Figure 1 A conventional LC-VCO according to the prior art is shown; Figure 2A A voltage-controlled oscillator circuit having functional elements for controlling a voltage-controlled oscillator according to an embodiment disclosed herein is shown; Figure 2B and Figure 2C An illustration of an embodiment disclosed herein is shown. and equivalent capacitance Example curves illustrating the relationship; Figure 3A A schematic equivalent diagram of an LC-VCO having a variable resistor for controlling the capacitance of the LC-VCO is shown according to an embodiment disclosed herein; Figure 3B An example of a parallel equivalent of a varistor capacitor block 202 according to an embodiment disclosed herein is shown; Figure 4A A hierarchical block diagram of an LC-VCO according to an embodiment disclosed herein is shown; Figure 4B A block diagram of an LC-VCO according to an embodiment disclosed herein is shown to illustrate a block diagram of the control block (404); Figure 4C A detailed block diagram of an LC-VCO according to an embodiment disclosed herein is shown; Figure 5 A schematic example of a voltage-controlled oscillator according to embodiments disclosed herein is shown; Figure 6 A flowchart of a method for controlling a voltage-controlled oscillator according to an embodiment disclosed herein is shown. Detailed Implementation

[0015] The embodiments herein, along with their various features and advantageous details, are explained more fully with reference to the non-limiting embodiments illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques have been omitted to avoid unnecessarily obscuring the embodiments herein. The examples used herein are intended only to help understand how the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Therefore, the examples should not be construed as limiting the scope of the embodiments herein.

[0016] For purposes of interpreting this specification, definitions (as defined herein) will be used, and where appropriate, terms used in the singular will also include the plural, and vice versa. It should be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Unless otherwise stated, the terms “comprising,” “having,” and “including” should be interpreted as open-ended terms.

[0017] The words / phrases “exemplary,” “example,” “illustration,” “in instance,” “etc.,” “e.g.,” “i.e.,” are used herein only to mean “served as an example, instance, or illustration.” Any embodiment or implementation of the subject matter described herein using the words / phrases “exemplary,” “example,” “illustration,” “in instance,” “etc.,” “e.g.,” “i.e.,” should not necessarily be construed as superior to or having an advantage over other embodiments.

[0018] Embodiments herein may be described and illustrated in the form of blocks that implement the described (one or more) functions. These blocks (which may be referred to herein as managers, units, modules, hardware components, etc.) are physically implemented by analog and / or digital circuitry (such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuitry, passive electronic components, active electronic components, optical components, hardwired circuitry, etc.) and optionally driven by firmware. These circuits may, for example, be implemented in one or more semiconductor chips or on a substrate support such as a printed circuit board. The circuitry constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware for performing certain functions of the block and a processor for performing other functions of the block. Each block of an embodiment may be physically separated into two or more interacting and discrete blocks without departing from the scope of this disclosure. Similarly, blocks of an embodiment may be physically combined into more complex blocks without departing from the scope of this disclosure.

[0019] It should be noted that the elements in the accompanying drawings are shown for descriptive and facilitative purposes and may not necessarily be drawn to scale. For example, flowcharts / sequence diagrams illustrate methods in the form of operations required to understand the aspects of the embodiments disclosed herein. Furthermore, regarding the construction of the apparatus, one or more components of the apparatus may be represented by conventional symbols in the accompanying drawings, and the drawings may show only specific details relevant to understanding the embodiments, so as not to obscure details that would be obvious to those skilled in the art through the description herein. Similarly, regarding the system, one or more components / modules constituting the system may be represented by conventional symbols in the accompanying drawings, and the drawings may show only specific details relevant to understanding the embodiments, so as not to obscure details that would be obvious to those skilled in the art through the description herein.

[0020] The accompanying drawings are provided to aid in the easy understanding of the various technical features, and it should be understood that the embodiments presented herein are not limited to the drawings. Therefore, this disclosure should be construed as extending to any modifications, equivalents, and substitutions, in addition to those specifically listed in the drawings and corresponding description. The use of terms such as first, second, third, etc., to describe components / elements / operations is for the purposes of this description and should not be construed as sequential ordering / placement / occurrence unless otherwise stated.

[0021] In short, the embodiments described herein can implement a voltage-controlled oscillator (VCO) by mapping a phase-locked loop control voltage (input control voltage) to an output control voltage (which in turn controls the equivalent capacitance within the VCO). Now refer to... Figures 2A to 6 An embodiment is shown, wherein similar reference numerals consistently denote corresponding features throughout all figures.

[0022] Figure 2A A voltage-controlled oscillator (VCO) circuit 200 with functional elements for controlling the VCO is shown. The functional element is a varistor-capacitor circuit (“block”) 202. The varistor-capacitor block 202 can be based on the concept of the equivalent capacitance observed from the source at a given frequency, and the equivalent capacitance varies. Other circuit components 102, 130, 104, 107, C5, and C6 (corresponding to capacitors C3 and C4) can be used in conjunction with those described above. Figure 1 The descriptions are the same or similar.

[0023] Figure 2B and Figure 2C An illustration of R according to an embodiment disclosed herein is shown. S and equivalent capacitance C EQ Example curves showing the relationship.

[0024] For example, consider source drive and resistor R S ( Figure 3A The equivalent resistance shown is connected in series with a 25fF capacitor, and the frequency ω0 = 6.28 × 24 GHz (where 6.28 equals 2π). Figure 2B As shown, when R S As the current scans from 0 to 2KΩ, the imaginary part of the source current changes with R. S It decreases continuously as it increases.

[0025]

[0026] Therefore, the equivalent capacitance "observed from the source" (C) EQ (The capacitance observed from the drains of transistors M1 and M2) is .

[0027] Due to the equivalent capacitance and RS The value is inversely proportional to the equivalent capacitance C, therefore the equivalent capacitance C EQ With R S The value increases and then decreases continuously, such as Figure 2C As shown.

[0028] In the embodiments described herein, the equivalent capacitance of the LC-VCO circuit can be altered using the quality factor. At the resonant frequency, the series impedance of the LC circuit is minimum, and the parallel impedance is maximum. Because resonance occurs at a specific frequency for a given inductance and capacitance value, the resonant frequency can be used for tuning and filtering the LC-VCO. Considering the series-parallel transformation of the RLC network, the equivalent parallel capacitance C... P (See) Figure 3B The following formula is given:

[0029] Equivalent parallel resistance R P (See) Figure 3B The following formula is given:

[0030] Since the inherent losses are the same at the resonant frequency, the quality factors of the two networks are the same. Therefore: and

[0031]

[0032] As can be seen from the above formula, reducing the quality factor can reduce the effective capacitance (C) observed in the LC tank circuit. P ).exist R S When =0 and Q=∞, the value of C is... P =C M , where C P This is the total LC tank capacitance when capacitors are connected in series. On the other hand, when Q=0 and R S When C = ∞, P It becomes 0. This is achieved by changing the value between 0 and ∞. R S The value of C P The value (effective capacitance observed from an LC tank circuit) can be between 0 and C. P Changes between them.

[0033] Changing the resistance value (the effective capacitance observed in an LC tank circuit) can be the basis for designing a variable capacitor at the resonant frequency.

[0034] In the embodiments described herein, the effective capacitance can be altered using the equivalent loss resistance. This is achieved by using a series-to-parallel transformation at the network's resonant frequency, resulting in an equivalent parallel resistance R. P It is given by the following formula:

[0035] The above formula uses the form In the case of, The minimum value is generated at Q=1; this occurs when Q=1.

[0036]

[0037] Therefore, R is generated at Q=1. P The minimum value of R, and the LC-VCO gain will be the lowest. When Q=1, R P for .

[0038] R P The minimum value is not R S The minimum bound, but C S The minimum bound of the maximum value is because R S The lower the value, the higher Q, resulting in a larger R. P Value. With the value of ω0 fixed, the constraint can be... C S At its maximum value. C S The maximum value and R S The range of possible values ​​together determines the tuning range. Therefore, by changing... R S The value of can change the capacitance.

[0039] In the embodiments described herein, it was observed that: by changing R S The value of C P The value can be 0 or... C S Changes between. For those close to C S C P Values, Q and R P Maximum. For C close to 0 P Values, Q and R P Minimum. In R P At the minimum value, the LC-VCO gain is lowest, which may be undesirable.

[0040] Figure 3AA schematic equivalent diagram of an LC-VCO 200 with a variable resistor for controlling the capacitance of an LC-VCO according to an embodiment disclosed herein is shown. Transistors M1 and M2 form a negative-gm circuit 104 to compensate for losses in the LC tank circuit. Capacitor bank 102 includes a capacitor that can be digitally controlled for initial frequency calibration. Varistor capacitor block 202 includes capacitor C. M and variable resistors R S C M and R S The equivalent value of the combined capacitance can be obtained from the variable resistor. R S Control. Variable resistor R S Together with a capacitor, they are called varistor capacitors. The assembly having a variable resistor for controlling the capacitance is hereby called a varistor capacitor. Capacitor C M This can include, but is not limited to, metallic capacitors. A capacitor can have any capacitance value, which can be changed using a variable resistor.

[0041] In the embodiments described herein, as observed, by changing R S The capacitance value can be between 0 and... C S The difference is changed by using a control voltage (V) CTRL To change the variable resistor R S The value of can change the C observed by the LC-VCO tank circuit. M The value of . Figure 3B An example of a parallel equivalent of a varistor capacitor block (202) according to an embodiment disclosed herein is shown. Parallel resistor R P It reaches its minimum value near Q=1. It should be noted that... R P The minimum value is the worst for LC-VCO gain.

[0042] Figure 4A A hierarchical block diagram of the LC-VCO 200 according to an embodiment disclosed herein is shown. Figure 5 yes Figure 4A A sample circuit diagram of the LC-VCO 200. (Reference) Figure 4A and Figure 5 The varistor-capacitor block 202 includes a MOS transistor device M. 3_N It can be used as a variable resistor in an LC-VCO. MOS device M 3_NIt can have a large range constraint to utilize the capacitance of the varistor capacitor block 202. (For example, a pair of capacitors C) M The entire range of the control voltage V from the PLL 411 (external to the LC-VCO 200 or included in the LC-VCO 200). CTRL (These can be interchangeably referred to as "input control voltage V") CTRL ) cannot be directly used to control MOS devices M 3_N Therefore, the LC-VCO 200 includes a control circuit (“block”) 404. The control block 404 controls the voltage V. CTRL The value is mapped to the control voltage V of the varistor capacitor block 202. CTRL_MAP "To control the equivalent capacitance of the varistor capacitor block 202. (Voltage V)" CTRL_MAP (In this document, it can be interchangeably referred to as the output control voltage of control circuit 404.) In other words, the output control voltage V CTRL_MAP Based on the input control voltage V from PLL 411 CTRL , where V CTRL_MAP The equivalent capacitance of the varistor capacitor block 202 is controlled (the equivalent capacitance is V). CTRL_MAP The function, and V CTRL_MAP Mapping to V CTRL ).

[0043] In the embodiments described herein, the MOS device is a variable resistor based on a voltage-controlled transistor (therefore, it can be interchangeably referred to as a "MOS transistor M"). 3_N ”). MOS device M 3_N Connected in series with at least one capacitor (e.g., left capacitor C) M And right capacitor C M That is, the left capacitor C M And right capacitor C M One end is connected to the drain of transistor M1 and the drain of transistor M2 respectively, and the left capacitor C M And right capacitor C M The opposite ends are respectively connected to transistor M 3_N (drain or source of the MOS device). 3_N and capacitor C M It is connected in parallel with the LC tank circuit 107. MOS device M 3_N and capacitor C M It is also connected to the negative transconductance circuit 104.

[0044] In the embodiments described herein, control block 404 is connected to MOS device M. 3_NThe gate input. Control block 404 includes an error amplifier 408 and a conversion circuit (“block”) 406 (e.g., performing voltage conversion and capacitor-to-voltage conversion). As described above, control block 404 can map the phase-locked loop control voltage to the capacitance value of varistor-capacitor block 202 via the MOS device in varistor-capacitor block 202.

[0045] Figure 4B An example block diagram of an LC-VCO 200 according to an embodiment disclosed herein is shown, wherein a block diagram of control block 404 is shown. Conversion block 406 includes a copy 410 of a varistor-capacitor block and a capacitor-to-voltage conversion circuit (“block”) 412. Conversion block 406 can generate a copy of the varistor capacitor in the copy 410 of the varistor-capacitor block. Conversion block 406 can generate an equivalent voltage Vc in the capacitor-to-voltage conversion block 412 for mapping the phase-locked loop control voltage to the capacitance of the varistor-capacitor block 202. CTRL_FB The error amplifier 408 can map the control voltage V of the varistor-capacitor block by using the equivalent voltage as a negative feedback input. CTRL_MAP Control voltage V CTRL This can be provided as a positive input to the error amplifier 408. The output of the error amplifier 408 is the control voltage V of the varistor-capacitor block. CTRL_MAP The control voltage V of the varistor-capacitor block CTRL_MAP It can be used to change the equivalent capacitance of the varistor capacitor block 202.

[0046] In the embodiments described herein, a copy 410 of the varistor capacitor block is generated by taking a phase-locked loop control voltage as input.

[0047] Figure 4C Detailed example block diagrams of an LC-VCO according to embodiments disclosed herein are shown. Reference will be made below. Figure 5 Example circuit discussion Figure 4C Copy 410 of the varistor capacitor block includes capacitor C. M and variable resistor R S MOS device M 3_N It can be used as a variable resistor. A MOS device can be a voltage-controlled transistor-based variable resistor. A MOS device can be used with at least one capacitor C. M Series connection. The copy 410 of the varistor-capacitor block may also include a switching element. The switching element may include, but is not limited to, having an input clock frequency F. VCO Inverter.

[0048] In the embodiments described herein, a copy 410 of the varistor capacitor block can generate a first current value. The first current value can be, but is not limited to, the switching current I. CVF and average current IAVG Switching elements with an input clock frequency F VCO An inverter with self-capacitance and parasitic capacitance can generate an average current. Capacitor C M Switching current can be generated together with switching elements. This is because an LC-VCO can operate only at the resonant frequency (i.e., the VCO frequency F). VCO The capacitance value can be detected only at the VCO frequency F. VCO C was sensed at the location M The capacitance value.

[0049] In the embodiments described herein, the capacitor-to-voltage conversion block 412 may include a first current mirror block 414. The first current mirror block 414 may mirror a first current value generated by a copy 410 of the varistor-capacitor block. The current through the first current mirror block 414 is generated by I... F express: .

[0050] In the embodiments described herein, the capacitor-to-voltage conversion block 412 may include an average current generation block 416. The average current generation block 416 may include a second switching element. The second switching element may be, but is not limited to, having an input clock frequency F. VCO The circuit consists of an inverter and a pair of current mirror circuits. The average current generating block 416 generates an average current. The generated average current is mirrored several times by the pair of current mirror circuits in the average current generating block 416. The value of the average current is equal to and opposite to the average current generated by the first current mirror block 414. The average current generated in the average current mirror block can be –I. AVG .

[0051] In the embodiments described herein, the total current I at node N is... SW It has a first current value from the first current mirror block 414 and an average current from the average current generation block 416. Since the average current from the average current generation block 416 is opposite to the first current value, the total current I at node N is... SW The total current at the location is:

[0052] Subtracting the average current from the first current value yields the capacitance C. M The switching current. The total current flowing through node N is I. CVF That is, consisting of a switching element and a capacitor C. M The switching current generated by the load.

[0053] In embodiments herein, the capacitor-to-voltage conversion block 412 may include a voltage generation circuit (“block”) 418. The voltage generation block 418 may draw voltage from the switching current I of a copy of the varistor-capacitor block 410.CVF Generation and varistor capacitor C M The corresponding equivalent voltage. Voltage generation block 418 may include a gain resistor R. GAIN Connect to voltage source V dd Current source I SHIFT and resistance R SHIFT The total current (i.e., the switching current) can flow from node N to voltage generation block 418. Therefore, the switching current can flow through R. GAIN Flowing through R GAIN The net current is I CVF = C M VF VCO The voltage generation block 418 can use voltages from I... CVF and R GAIN The mapping function generates the equivalent voltage.

[0054] In the embodiments described herein, the voltage generation block 418 forces the equivalent voltage value to be equal to the phase-locked loop control voltage. The equivalent voltage is provided to the error amplifier 408 to generate the control voltage V of the mapped varistor-capacitor block. CTRL_MAP The equivalent voltage is used to map the phase-locked loop control voltage to the capacitance of the varistor capacitor block 202. Since the value of the equivalent voltage is forced to be equal to the phase-locked loop control voltage, V... CTRL = V CTRL_FB .

[0055]

[0056] This is the maximum signal transfer function.

[0057] Because of V SHIFT With I CVF The change is very small; therefore, this is the minimum signal transfer function.

[0058]

[0059] Regarding ΔC M The obtained transfer function is derived from the control voltage V CTRL The small-signal transfer function is derived from the varistor capacitor in the LC-VCO. This transfer function maps the phase-locked loop control voltage to the equivalent voltage generated by control block 404. The resulting transfer function is a programmable offset from the switching current, where the switching current changes the capacitance ΔC. M The value of . The error amplifier 408 uses the transfer function to generate the control voltage V of the mapped varistor-capacitor block 202. CTRL_MAP It is used to change the capacitance ΔC M The value of V. Therefore, by changing V CTRL The value of capacitor CM The value also changes.

[0060] Figure 5 A schematic example of a voltage-controlled oscillator 200 according to an embodiment disclosed herein is shown. The upper portion of the LC tank path can be the same as described above. Therefore, transistor M 1_N and M 2_N A negative-gm circuit 104 is formed to compensate for losses in the LC tank circuit. The capacitor bank 102 includes capacitors that can be digitally controlled for initial frequency calibration. An inductor-capacitor (LC) tank circuit 107, including a center-tapped inductor, is connected in parallel with the capacitor bank 102 without a varactor diode. The LC tank circuit resonates to generate an oscillating voltage at a specific frequency. The supply voltage of the LC_VCO is labeled V. LDO It is generated by a voltage regulator. Because the frequency range of the LC-VCO depends on the ratio of the controllable tank circuit capacitance to the total tank circuit capacitance, it is controlled by the varistor capacitor block 202.

[0061] In the embodiments described herein, the varistor capacitor block 202 includes a MOS device M that functions as a variable resistor in an LC-VCO. 3_N MOS device M 3_N With a large range constraint, the capacitance C of the varistor capacitor block 202 can be utilized. M The entire range. Control voltage V from PLL 411. CTRL It cannot be directly used to control MOS devices M 3_N Therefore, the LC-VCO includes a control block 404. Control block 404 controls the voltage V. CTRL The value is mapped to the control voltage V of the varistor-capacitor block. CTRL_MAP Value, to control the MOS device M 3_N This controls the equivalent capacitance of the varistor capacitor block 202. In other words, the output control voltage V... CTRL_MAP Based on the input control voltage V from PLL 411 CTRL , where V CTRL_MAP The equivalent capacitance of the varistor capacitor block 202 is controlled (the equivalent capacitance is V). CTRL_MAP The function, and V CTRL_MAP Mapping to V CTRL ).

[0062] In the embodiments described herein, control block 404 includes a switching block 406 and an error amplifier 408. Switching block 406 includes a copy 410 of a varistor-capacitor block, wherein the copy includes a voltage-controlled transistor M'. 3_N (corresponding to transistor M) 3_N ) and multiple capacitors C' M (All correspond to the capacitors in the varistor-capacitor circuit 202) Control block 404 includes a first current mirror block 414 and an average current generation block 416. Transistor M in the first current mirror block 414... 4_P_CVF and M 5_P_CVF It is a current mirror pair. Similarly, the transistor (M) in the average current generation block 416 6_P_A M 7_P_A ) and (M 8_N_A M 9_N_A () is a current mirror pair. Transistor M 5_P_CVF M 7_P_A and M 9_N_A It is a current-controlled current source. Current flows through M. 4_P_CVF The current is:

[0063] C M VF VCO It is based on the input clock frequency F VCO And the capacitive load is C M The switching current driven by the inverter, C SELF VF VCO It is based on the input clock frequency F VCO And it only has the average current driven by an inverter with self-capacitive load and parasitic capacitance. Because the LC-VCO only operates at the resonant frequency (i.e., the VCO frequency F). VCO The capacitance value is detected at point ), so the capacitance C is... M The value is only at VCO frequency F VCO The location was sensed. In the embodiments described herein, a current mirror pair (M) is added to the average current generation block 416. 6_P_A M 7_P_A ) and (M 8_N_A M 9_N_A This is to subtract the average current term related to short-circuit current, self-load capacitance, and parasitic capacitance current. Therefore, through M... 5_P_CVF Inflow V CTRL_FB The current at the node is: .

[0064] Through M 9_N_A Inflow V CTRL_FB The current at the node is: I AVG .

[0065] From V CTRL_FB The node current flows to (capacitor-to-voltage converter 412) R GAIN The net current is I CVF = C M VF VCO .

[0066] Switching current I CVF For establishing from the control voltage V CTRL The mapping function to the variable capacitor is very important.

[0067] The equivalent voltage obtained from control block 404 is forced to be equal to the control voltage, i.e., the phase-locked loop control voltage.

[0068]

[0069] Error amplifier 408 uses a transfer function to generate a control voltage (V) for the mapped varistor-capacitor block 202 (i.e., V). CTRL_MAP ), where the control voltage (V) (i.e., V) CTRL_MAP Used to change the capacitance value ΔC M Therefore, by changing V CTRL The value of capacitor C M The value also changes accordingly.

[0070] The obtained transfer function is derived from the control voltage V CTRL The small-signal transfer function of the varistor and capacitor in the LC-VCO. The mapping of the phase-locked loop control voltage makes the voltage-controlled oscillator satisfy the following constraints: such as, the LC-VCO is linear and time-invariant, non-inverting, monotonic, and uses V CTRL The variable frequency, and has infinite or near-infinite resolution by checking the ratio of the controllable capacitor to the total capacitance.

[0071] In one example scenario, when testing the LC-VCO, its performance showed a 20% higher frequency range achieved with a single LC-VCO over a wide frequency range. The maximum achievable frequency is 6% higher than that of a conventional LC-VCO. For example, this voltage-controlled oscillator circuit enables the design of a 28GHz LC-VCO for high-speed serializers / deserializers (SerDes) with less design effort. A 20% area reduction is achieved compared to a dual LC-VCO solution.

[0072] Voltage-controlled oscillator (VCO) circuits can support protocols with multiple data rates. LC-VCOs exhibit lower deterministic jitter and power supply-induced jitter. Due to their improved power supply rejection ratio (PSRR), they also offer better performance compared to VCOs. CTRL Compared to shift control, it exhibits lower phase shift and UPDN mismatch. The Kvco range of the LC-VCO can be programmed over a 10-fold range. This wide Kvco range provides variation for PLL bandwidth control to optimize jitter and stability margins.

[0073] Figure 6A method 600 for controlling a voltage-controlled oscillator (VCO) according to an embodiment disclosed herein is shown. This method can be applied to control the aforementioned LC-VCO 200 or similar circuit. In operation 602, a first current value is generated by a copy 410 of the varistor-capacitor block. The first current value includes a switching current and an average current. The switching current is generated by a first switching element under the capacitance of a varistor capacitor loaded onto the varistor-capacitor block (e.g., 202). The average current is generated by the first switching element under its self-loaded capacitance. In operation 604, the first current value is mirrored by a first current mirror block (e.g., 414). In operation 606, an average current is generated by a pair of current mirror circuits in an average current generation block (e.g., 416). The average current is generated by a second switching element under its self-loaded capacitance. The generated average current is the opposite of the value of the average current passing through the first current mirror block.

[0074] In operation 608, the switching current at node (e.g., N) is obtained from the first current value by subtracting the average current from the first current value. In operation 610, an equivalent voltage corresponding to the varistor capacitor is generated from the switching current by a voltage generation block (e.g., 418) of a control block (e.g., 404). In operation 612, the phase-locked loop control voltage is mapped to the capacitance of the varistor capacitor block by an error amplifier (e.g., 408) through a voltage-controlled transistor in the varistor capacitor block. The value of the equivalent voltage is forced to be equal to the phase-locked loop control voltage by the control block. The equivalent voltage is used to map the phase-locked loop control voltage to the capacitance value of the varistor capacitor block. Some or all of the various actions in method 600 may be performed in the presented order, in a different order, or simultaneously (if possible). Furthermore, in some embodiments, [the following may be omitted]. Figure 6 Some of the actions listed in the document.

[0075] The method can be implemented in at least one embodiment by a software program written in, for example, the Hardware Description Language for High-Speed ​​Integrated Circuits (VHDL) or another programming language, or by running one or more VHDLs on at least one hardware device. The device may also include, for example, hardware devices (e.g., ASICs), or a combination of hardware and software devices (e.g., ASICs and FPGAs), or at least one microprocessor and at least one memory having software modules located therein. The method embodiments described herein can be implemented partly in hardware and partly in software. Alternatively, embodiments can be implemented on different hardware devices (e.g., using multiple CPUs).

[0076] The foregoing description of specific embodiments will fully reveal the general nature of the embodiments herein, enabling others to readily modify and / or adapt these specific embodiments for various applications by applying existing knowledge without departing from the overall concept. Therefore, such modifications and adaptations should and are intended to be understood as being within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology used herein is for descriptive purposes and not for limitation. Therefore, although embodiments and examples have been described herein, those skilled in the art will recognize that the embodiments and examples disclosed herein can be practiced in a modified manner within the scope of the embodiments described herein.

Claims

1. A voltage-controlled oscillator circuit, the voltage-controlled oscillator circuit comprising: An inductor-capacitor tank circuit, the inductor-capacitor tank circuit including a center-tapped inductor connected in parallel with a capacitor bank without varactor diodes, wherein the inductor-capacitor tank circuit resonates to generate an oscillating voltage at a specific frequency; and A control circuit is connected to a varistor-capacitor circuit, wherein the varistor-capacitor circuit includes a voltage-controlled transistor-based variable resistor connected in series with at least one capacitor, the varistor-capacitor circuit is connected in parallel with the inductor-capacitor tank circuit, and is connected to the negative transconductance circuit. The control circuit includes an error amplifier and a conversion circuit, and is configured to generate an output control voltage based on the input phase-locked loop control voltage. The output control voltage controls the capacitance value of the varistor-capacitor circuit through the voltage-controlled transistor-based variable resistor.

2. The voltage-controlled oscillator circuit according to claim 1, wherein, The conversion circuit generates: A copy of the capacitor in the varistor-capacitor circuit; and The output voltage serves as the equivalent voltage of the capacitor used to map the phase-locked loop control voltage to the capacitor of the varistor-capacitor circuit.

3. The voltage-controlled oscillator circuit according to claim 2, wherein, The conversion circuit includes: A copy of the varistor-capacitor circuit; and A capacitor-to-voltage conversion circuit, wherein the capacitor-to-voltage conversion circuit includes: A first current mirror circuit is configured to mirror a first current value generated by a copy of the varistor-capacitor circuit, wherein the first current value includes a switching current and an average current. An average current generation circuit, configured to generate the average current, wherein the average current is subtracted from the first current value to obtain the switching current reflecting the capacitor; and A voltage generation circuit configured to generate an equivalent voltage corresponding to the varistor capacitor from the switching current of a copy of the varistor capacitor circuit. Wherein, the voltage generation circuit forces the value of the equivalent voltage to be equal to the phase-locked loop control voltage, and The equivalent voltage is used to map the phase-locked loop control voltage to the capacitance of the varistor-capacitor circuit.

4. The voltage-controlled oscillator circuit according to claim 3, wherein, The copy of the varistor-capacitor circuit includes a first switching element that drives the copy of the varistor-capacitor circuit to generate the average current and the switching current.

5. The voltage-controlled oscillator circuit according to claim 3, wherein, The average current generation circuit includes a second switching element.

6. The voltage-controlled oscillator circuit according to claim 1, wherein, The negative transconductance circuit is configured to compensate for the losses of the inductor-capacitor tank circuit.

7. The voltage-controlled oscillator circuit according to claim 1, wherein, The voltage-controlled oscillator circuit is at least one of a system-on-a-chip circuit and a semiconductor integrated circuit chip circuit.

8. A method for controlling a voltage-controlled oscillator, the method comprising: The voltage generation circuit of the control circuit generates an equivalent voltage from the switching current that corresponds to the varistor and capacitor of the voltage-controlled oscillator; as well as The error amplifier maps the input control voltage to the capacitance of the varistor-capacitor circuit via the voltage-controlled transistor in the varistor-capacitor circuit. The equivalent voltage is forced to equal the input control voltage by the control circuit, and the equivalent voltage is used to map the input control voltage to the capacitance value of the varistor-capacitor circuit.

9. The method according to claim 8, further comprising: The first current value is generated by a copy of the varistor-capacitor circuit; The average current is generated by the average current generation circuit; The switching current is obtained by subtracting the average current from the first current value.

10. The method according to claim 9, further comprising: The mirror image is generated by a copy of the varistor-capacitor circuit, wherein the first current value includes the switching current and the average current.

11. The method according to claim 8, wherein, The switching current includes a programmable offset component added to the switching current to change the capacitance value of the varistor-capacitor circuit.

12. The method according to claim 8, wherein, The input control voltage is a phase-locked loop control voltage.

13. A voltage-controlled oscillator circuit, the voltage-controlled oscillator circuit comprising: An inductor-capacitor tank circuit, the inductor-capacitor tank circuit including a center-tapped inductor connected in parallel with a capacitor bank without varactor diodes, wherein the inductor-capacitor tank circuit resonates to generate an oscillating voltage; and A control circuit is connected to a varistor-capacitor circuit, wherein the varistor-capacitor circuit includes a voltage-controlled transistor-based variable resistor connected in series with at least one capacitor, the varistor-capacitor circuit is connected in parallel with the inductor-capacitor tank circuit, and is also connected in parallel with the negative transconductance circuit. The control circuit includes an error amplifier and a conversion circuit, and is configured to generate an output control voltage based on an input control voltage. The output control voltage controls the capacitance value of the varistor-capacitor circuit through the voltage-controlled transistor-based variable resistor.

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