Ring oscillator

Abstract

Ring Oscillator This description concerns a control circuit (120) for the output signal (Out100) of a ring oscillator (110) at a given frequency, comprising: - a first transistor (T121) of a first type adapted to receive a control voltage (Vctrl120) at its control terminal and adapted to supply a first control current (I121) at a given frequency at a first conduction terminal; - a second transistor (T122) of a second type, different from the first type, adapted to receive said control voltage (Vctrl120) at its control terminal, and adapted to supply a second current (I122) at a second conduction terminal of said first transistor (T121). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Ring oscillator technical field

[0001] This description relates generally to electronic systems and devices, and more particularly to control circuits for electronic systems and devices. More specifically, this description relates to a ring oscillator and its frequency control circuit. Previous technique

[0002] There are a multitude of circuits for generating signals, and in particular for generating periodic signals.

[0003] Ring oscillators are well-known circuits for generating periodic signals, which are often used to generate clock signals.

[0004] It would be desirable to be able to improve, at least in part, certain aspects of known signal generation circuits, and in particular, certain aspects of known control circuits of signal generation circuits. Summary of the invention

[0005] There is a need for a frequency control circuit for a signal supplied by a more precise ring oscillator.

[0006] There is a need for a method of controlling the frequency of a signal supplied by a more precise ring oscillator.

[0007] There is a need for a more precise ring oscillator.

[0008] One embodiment overcomes all or part of the drawbacks of known frequency control circuits of a ring oscillator.

[0009] One embodiment overcomes all or part of the drawbacks of known frequency control methods of a ring oscillator.

[0010] One embodiment overcomes all or part of the disadvantages of ring oscillators.

[0011] One embodiment provides for the addition, to the control current supplied by said control circuit, of a current inversely proportional to a control voltage of the frequency of the control circuit.

[0012] One embodiment provides a frequency control circuit for an output signal of a ring oscillator comprising: - a first transistor of a first type adapted to receive a control voltage on its control terminal and adapted to provide a first frequency control current on a first conduction terminal; - a second transistor of a second type, different from the first type, adapted to receive said control voltage on its control terminal, and adapted to supply a second current to a second conduction terminal of said first transistor.

[0013] Another embodiment provides a method for controlling the frequency of an output signal of a ring oscillator using a circuit comprising: - a first transistor of a first type adapted to receive a control voltage on its control terminal and adapted to provide a first frequency control current on a first conduction terminal; - a second transistor of a second type, different from the first type, adapted to receive said control voltage on its control terminal, and adapted to supply a second current to a second conduction terminal of said first transistor.

[0014] According to one embodiment, said first and second transistors are MOS transistors.

[0015] According to one embodiment: - said first transistor is an NMOS type transistor; and - said second transistor is a PMOS type transistor.

[0016] According to one embodiment, said first and second transistors are bipolar transistors.

[0017] According to one embodiment: - said first transistor is an NPN type transistor; and - said second transistor is a PNP type transistor.

[0018] According to one embodiment, said second transistor is adapted to supply said second current via a current mirror.

[0019] According to one embodiment, said second conduction terminal of said first transistor is connected to a resistor.

[0020] Another embodiment provides for a ring oscillator comprising a circuit described above.

[0021] Another embodiment provides for an electronic device comprising an oscillator described above.

[0022] According to one embodiment, the device is a phase-locked loop.

[0023] Another embodiment provides for an electronic system comprising a device described previously.

[0024] According to one embodiment, the system is a controller, a microcontroller, a processor, or a microprocessor. Brief description of the drawings

[0025] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0026] [Fig.1] represents an embodiment of a ring oscillator and its frequency control circuit;

[0027] [Fig.2] represents curves illustrating the operation of the control circuit of [Fig.1];

[0028] Figure 3 represents an electronic device using the embodiment of the [Fig. 1] ; and

[0029] [Fig.4] represents an electronic system using the embodiment of [Fig.1]. Description of the implementation methods

[0030] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0031] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0032] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0033] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0034] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0035] The embodiments described below relate to the adjustment of a frequency control signal for a ring oscillator. More particularly, these embodiments utilize the addition of a current inversely proportional to a control voltage across one terminal of a transistor providing a frequency control current. These embodiments are described with reference to Figures 1 and 2.

[0036] Furthermore, the embodiments described below are particularly well suited for use in a phase-locked loop (PLL), by An example is a phase-locked loop used in a microcontroller. These applications are described in more detail in relation to Figures 3 and 4.

[0037] Furthermore, the embodiments described above are particularly suitable for use in any type of industrial market where the use of a ring oscillator is required. More specifically, such a ring oscillator may be intended for: - the automotive industry, for example in the field of automotive electrification or in the field of Advanced Driver Assistance Systems (ADAS); - the industrial industry, for example in the field of green energy, in the field of infrastructure electrification, the Internet of Things (IoT) and Smart Homes, where electricity and energy consumption and data exchange are key elements; - the personal electronics industry, for example in the field of mobile telephony and the Internet of Things (IoT), as well as in the field of broadband interfaces; and - the communications equipment, computer and peripherals industry, for example in the field of infrastructure and data centers, and in the field of low Earth Orbit (LEO) satellites.

[0038] Fig. 1 represents an embodiment of an electronic circuit 100 for generating a periodic signal.

[0039] According to one embodiment, the circuit 100 is a ring oscillator (RO) accompanied by its output signal frequency control circuit. In other words, the circuit 100 comprises: - a ring oscillator 110; and - a control circuit 120 for the frequency of an output signal OutlOO of the ring oscillator 110.

[0040] In one embodiment, the ring oscillator 110 is adapted to provide the output signal OutlOO. This OutlOO signal is a periodic signal, for example, a signal that can serve as a clock signal. In one embodiment, the frequency of the OutlOO signal is set, fixed, changed, or controlled via a control current 1121 supplied by the control circuit 120.

[0041] According to one example, the ring oscillator 110 comprises at least two differential input and output amplifiers Ampl 11 and Ampl 112. The outputs of amplifier Ampl 11 are connected, preferably connected, to the inputs of amplifier Ampl 12. The outputs of amplifier Ampl 12 are connected, preferably connected, to the inputs of amplifier Ampl 11. According to one example, Amplifiers Ampl 11 and Ampl 112 are suitable for use with a supply voltage Vdd100. As an example, amplifiers Ampl 11 and Ampl 12 are suitable for receiving the control current 1121 at their control terminals. Other ring oscillator structures can be used here and are within the scope of those skilled in the art. In particular, any ring oscillator capable of receiving frequency-based current control is compatible with the control circuit 120.

[0042] According to one embodiment, the control circuit 120 comprises a transistor T121 of a first type and a resistor R120. A first conduction terminal of transistor T121 is adapted to supply the control current 1121, and a second conduction terminal of transistor T121 is connected, preferably connected, to a first terminal of resistor R120. A second conduction terminal of resistor R120 is connected, preferably connected, to a node adapted to supply a reference voltage GND100, for example, ground. A control terminal of transistor T121 is adapted to receive a control voltage Vctrll20.

[0043] According to one embodiment, the control circuit 120 further comprises a current source CS 120 and a second-type transistor T122. A reference terminal of the current source CS 120 is connected, preferably connected, to the node providing the reference voltage GND100. An output terminal of the current source CS 120 is connected, preferably connected, to a first conduction terminal of the transistor T122. A second conduction terminal of the transistor T122 is connected to the midpoint between the transistor T121 and the resistor R120 via a transmission means detailed below and provides a current 1122. A control terminal of the transistor T122 is adapted to receive the control voltage Vctrll20.

[0044] According to one embodiment, transistors T121 and T122 are transistors of the same technology but of different types. In other words, transistor T121 is of a first type and transistor T122 is of a second type different from the first type. More specifically, transistors T121 and T122 react in opposite ways to the control voltage Vctrll20. Even more specifically, transistor T121 becomes increasingly conductive as a function of a first variation in the control voltage Vctrll20, while for the same variation, transistor T122 becomes less and less conductive, and vice versa.

[0045] According to one embodiment, the control circuit 120 further comprises a current transmission means 1122, or current copying means, delivered by transistor T122 to the midpoint between transistor T121 and resistor R120. In one example, this means is a current mirror assembly, or current mirror, comprising two transistors T123 and T124. In one example, a first conduction terminal of transistor T123 is connected, preferably connected, to the second The conduction terminal of transistor T122 and the control terminals of transistors T123 and T124 are connected. One conduction terminal of transistor T124 is preferably connected to the midpoint between transistor T121 and resistor R120. The second conduction terminals of transistors T123 and T124 are preferably connected to the terminal supplying the supply voltage VddlOO.

[0046] According to a first embodiment, transistors T121 and T122, and, in one example, transistors T123 and T124, are all metal-oxide-semiconductor field-effect transistors (MOSFETs). Furthermore, transistor T121 is an N-channel MOS transistor. In addition, transistor T122 is a P-channel MOS transistor. In one example, transistors T123 and T124 are PMOS transistors.

[0047] According to a second embodiment, transistors T121 and T122, as well as, by way of example, transistors T123 and T124, are all bipolar transistors. Furthermore, transistor T121 is an NPN transistor, and transistor T122 is a PNP transistor. By way of example, transistors T123 and T124 are PNP transistors.

[0048] According to one embodiment, a method for controlling the frequency of the output signal OutlOO of the ring oscillator 110 is as follows. A control voltage is applied to the control circuit 120; this voltage makes transistor T121 conductive and transistor T122 non-conductive, or vice versa, and more particularly, increases the value of the current 1121 supplied by transistor T121 and reduces the value of the current 1122 supplied by transistor T122, or vice versa.

[0049] Fig. 2 is a graph comprising curves illustrating the operation of the circuit 100 described in relation to Fig. 1.

[0050] The graph in [Fig.2] includes, more specifically: - a curve 201 illustrating a simulation of the evolution of the frequency of an output signal of a circuit similar to circuit 100 of [Fig.1] but not including transistor T122, current source CS 120 and current transmission means, as a function of the value of the control voltage Vctrll20, in the case where circuit 100 has a gain of 125 degrees and a fast implementation; - a curve 202 illustrating the evolution of the frequency of the output signal OutlOO of circuit 100 of [Fig.1] as a function of the value of the control voltage Vctrll20, in the case where circuit 100 has a gain of 125 degrees and is implemented quickly; and - a curve 203 illustrating the evolution of the frequency of the output signal OutlOO of the circuit 100 of [Fig.l] as a function of the value of the control voltage Vctrll20, in the case where the circuit 100 has a gain of -40 degrees and a slow implementation.

[0051] Also represented in [Fig.2] are a maximum frequency Fmax, a minimum frequency Fmin, and a minimum voltage Vmin.

[0052] The advantage of adding current 1122, that is, of using transistor 1122, current source CS 120, and the transmission means, is that it allows circuit 100 to provide an output signal with a frequency between the frequencies Fmin and Fmax as soon as the control voltage Vctrll20 is greater than the voltage Vmin, when the circuit gain is adapted for a case of rapid implementation at a high temperature. It should be noted that this result is not achieved when current 1122 is not added.

[0053] Fig. 3 represents schematically and in block form an embodiment of an electronic device 300 using the circuit 100 described in relation to Fig. 1.

[0054] According to one example, the electronic device 300 is a phase-locked loop (PLL). According to a particular example, the device 300 is a phase-locked loop adapted to receive, at its input, a signal at a first frequency Fin300 and to provide, at its output, a signal at a second frequency Fout300 which is a multiple of the first frequency Fin300.

[0055] For this purpose, device 300 may include: - an input circuit 301 (PFD + Constance Prost-Loop); - a 302 (RC filter) filtering circuit; - a circuit 303 (RO) of the type of circuit 100 described in relation to [Fig.1]; and - a circuit 304.

[0056] The circuit 301 is adapted to receive the input signal of frequency Fin300. According to one example, the circuit 301 includes a phase-frequency detector (PFD), and a charge pump (CP).

[0057] The circuit 302 (RC filtering) is adapted to receive an output signal from the circuit 301, and to provide, at the output, a control voltage Vctrl300 to the circuit 303. According to an example, the circuit 302 is an RC type filtering circuit, that is to say of the resistance-capacitor type.

[0058] Circuit 303 (RO) is of the type of circuit 100 described in relation to [Fig. 1]. Circuit 303 is adapted to receive the control voltage Vctrl300 from circuit 302 and to provide the output signal at frequency Fout300.

[0059] Circuit 304 is a feedback circuit adapted to receive the output signal of frequency Fout300 and to supply it as input to circuit 301.

[0060] Other applications of the circuit 100 described in relation to [Fig.1] are within the reach of a person skilled in the art.

[0061] Fig. 4 represents schematically and in block form an embodiment of an electronic system 400 using the circuit 300 described in relation to Fig. 3.

[0062] According to one example, system 400 is a complex electronic system, such as a controller, a microcontroller, a processor, or a microprocessor. According to a particular example, system 400 is a microcontroller.

[0063] According to one example, system 400 comprises: - one or more 401 (DIGITAL) digital circuits; - at least one 402 power management unit (PMU); - one or more 403 analog-to-digital conversion (ADC) circuits; - one or more 404 digital-to-analog conversion (DAC) circuits; - one or more phase-locked loops 405 (PLL); and - at least one 407 reset circuit (Reset).

[0064] Other applications of the device 300 described in relation to [Fig.3] are within the reach of a person skilled in the art.

[0065] Various embodiments and variations have been described. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0066] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. A frequency control circuit (120) of an output signal (OutlOO) of a ring oscillator (110) comprising: - a first transistor (T 121) of a first type adapted to receive a control voltage (Vctrll20) on its control terminal and adapted to supply a first control current (I121) of frequency on a first conduction terminal; - a second transistor (T 122) of a second type, different from the first type, adapted to receive said control voltage (Vctrll20) on its control terminal, and adapted to supply a second current (I122) to a second conduction terminal of said first transistor (T 121).

2. Circuit according to claim 1, wherein said first and second transistors (T121, T122) are MOS transistors.

3. Circuit according to claim 2, wherein: - said first transistor (T 121) is an NMOS type transistor; and - said second transistor (T 122) is a PMOS type transistor.

4. Circuit according to claim 1, wherein said first and second transistors (T121, T122) are bipolar transistors.

5. Circuit according to claim 4, wherein: - said first transistor (T 121) is an NPN type transistor; and - said second transistor (T 122) is a PNP type transistor.

6. Circuit according to any one of claims 1, 3 to 5, wherein said second transistor (T122) is adapted to supply said second current via a current mirror.

7. Circuit according to any one of claims 1, 3 to 6, wherein said second conduction terminal of said first transistor (T 121) is connected to a resistor (R 120).

8. Ring oscillator (100) comprising a circuit according to any one of claims 1, 3 to 7.

9. Electronic device (300) comprising an oscillator according to claim 8.

10. Device according to claim 9, being a phase-locked loop.

11. Electronic system (400) comprising a device according to claim 9 or 10.

12.

13. System according to claim 11, being a controller, a microcontroller, a processor, or a microprocessor. Method for controlling the frequency of an output signal of a ring oscillator using a circuit comprising: - a first transistor (T 121) of a first type adapted to receive a control voltage (Vctrll20) on its control terminal and adapted to provide a first control current (1121) of frequency on a first conduction terminal; - a second transistor (T 122) of a second type, different from the first type, adapted to receive said control voltage (Vctrll20) on its control terminal, and adapted to supply a second current (1122) to a second conduction terminal of said first transistor (T 121).

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