Electronic control device

Abstract

The invention relates to an electronic control device (200) comprising: a first input (201) for a control voltage (Vtune) of the voltage control device (200); a second input (202) for a reference control voltage (Vtune0) of the voltage control device (200); and an output (203), wherein the electronic control device (200) is configured to provide a bias current change ([delta] IB) to the voltage control device (200) via the output (203) in order to maintain a level of the control voltage (Vtune) within a specified range.

Description

Technical Field

[0001] The present disclosure relates to an electronic control device. In addition, the present disclosure relates to a method of operating an electronic control device. Background Art

[0002] Voltage controlled oscillators (LC-VCOs) are currently the most advanced in high performance PLLs due to their low phase noise properties. The frequency of the VCO is fine-tuned by the PLL acting on a voltage controlled capacitor. The input is called the control voltage Vtune. Sometimes, the VCO also integrates coarse tunability with a digital control capacitor to extend the operating range. Such digital control capacitors are calibrated before the PLL can start controlling and fine-tuning the frequency. Due to the limited range of control voltages used to correct frequency drift in the LC-VCO, the ability of applications running with a locked PLL to adapt to temperature drift or long-term continuous operation is often constrained without recalibrating the digital control capacitor (if it exists). In fact, temperature drift causes a change in the output frequency of the oscillator when the control voltage is kept constant in an open-loop configuration, while in a closed-loop configuration the loop attempts to offset the frequency change by adjusting the control voltage until the power supply (VDD) range of the PLL allows. Therefore, the tuning voltage eventually becomes a bottleneck, especially because the VDD space becomes lower for more advanced CMOS technology nodes, leaving less room for the loop to offset. Therefore, a strong temperature change that has locked the PLL can quickly cause the PLL to fall out of lock.

[0003] It is possible to use a second point injection in the oscillator to compensate for the drift via an additional varactor, but this results in additional parasitic effects in the LC tank, which may limit the tuning range, restrict the maximum operating frequency, increase the power or affect the overall noise.

[0004] Conventional bias current based compensation techniques use a combination of PTAT / CTAT (proportional to absolute temperature / complementary to absolute temperature) currents fed to the bias current node of the VCO to counteract temperature induced frequency drift. Such compensation relies solely on the temperature coefficient of the current. Therefore, the temperature, which can be considered as a second reference input (in addition to the tuning voltage), acts on the system in an open loop configuration. Any frequency error that may occur due to improper bias current adaptation can therefore only be compensated by the main loop of the PLL (via tuning voltage adaptation).

[0005] US 9 413 366 B2 discloses a device and a method for a phase locked loop with a temperature compensated calibration voltage.

[0006] US 8 803 616 B2 discloses temperature compensation and coarse tuning of group switches in a low phase noise VCO.

[0007] US 8 466 750 B2 discloses a VCO with temperature dependent biasing using an auxiliary varactor. Summary of the invention

[0008] A first aspect of the present disclosure is directed to an electronic control device, comprising:

[0009] - a first input for a control voltage of the voltage control device;

[0010] - a second input for a reference control voltage of the voltage control means; and

[0011] - output, where

[0012] - the electronic control means is configured to provide a bias current change to the voltage control means via the output in order to maintain the level of the control voltage within a specified range.

[0013] Another aspect of the present disclosure is directed to a method of operating an electronic control device, comprising the steps of:

[0014] - receiving a control voltage of a voltage control device and a reference control voltage; and

[0015] - A bias current change is provided to the voltage controlled device in such a way that the level of the control voltage remains within a specified range.

[0016] In this way, by means of the proposed electronic control device and the proposed method, the voltage-controlled device is at least partially controlled by means of the bias current. Advantageously, no additional control elements are required, which in fact achieves an effective temperature desensitization of the voltage-controlled device. It is not necessary to design the voltage-controlled device to incorporate the control characteristics by means of the electronic control device.

[0017] In one or more embodiments, the electronic control device is configured to minimize the difference between the control voltages.

[0018] In one or more embodiments, the control voltage is implemented in a first control loop of the voltage control device, wherein the electronic control device is implemented in an additional control loop of the voltage control device. In this way, a loop-based arrangement is implemented, which can be easily controlled.

[0019] In one or more embodiments, the control loops have different time constants, wherein the first control loop has a fast behavior to track changes affecting the frequency synthesizer, wherein the additional control loop has a slow behavior to follow temperature changes. In this context, "fast behavior" is typically in the microsecond range, and "slow behavior" is typically in the millisecond range or greater.

[0020] In one or more embodiments, the electronic control device is configured to correct temperature drift of the voltage control device by adapting the control voltage.

[0021] In one or more embodiments, the electronic control device is configured to maintain the dependency of the control voltage on the supply voltage. In this way, the specified operating characteristics of the electronic control device are supported.

[0022] In one or more embodiments, the electronic control device is configured to maintain the control voltage within a specified range relative to the supply voltage.

[0023] In one or more embodiments, the electronic control device is configured to control a frequency synthesizer based on an LC oscillator.

[0024] In one or more embodiments, the electronic control device comprises the following blocks functionally coupled in series with each other: differential amplifier, low pass filter, voltage-to-current (V2I) converter. With the help of the low pass filter, the control loop characteristics (eg with respect to time constant) can be appropriately designed.

[0025] In one or more embodiments, the electronic control device is configured to artificially generate additional VCO gain by measuring a tuning voltage shift, converting the voltage shift to a current, and feeding the resulting bias current change to a voltage controlled oscillator of the voltage control device.

[0026] In one or more embodiments, the electronic control device is configured to derive the required transconductance in the voltage-to-current converter given the bias current sensitivity of the VCO in order to implement temperature compensation / artificial VCO gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above discussion / overview is not intended to describe every embodiment or every implementation of the present disclosure. The drawings and the following detailed description also illustrate various embodiments. The aspects defined above and further aspects of the present disclosure are apparent from the examples of embodiments to be described below with reference to the drawings, which are illustrated with reference to the examples of embodiments. However, the present disclosure is not limited to the examples of embodiments.

[0028] All illustrations in the drawings are schematic. It should be noted that in different figures, similar or identical elements or features have the same reference numerals or have reference numerals that differ from the corresponding reference numerals only within the first digit. In order to avoid unnecessary repetitions, elements or features that have already been explained with respect to previously described embodiments will not be explained again at a later point in the description.

[0029] Various example embodiments may be more fully understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

[0030] Figure 1 A conventional control loop based frequency synthesizer is shown;

[0031] Figure 2is a diagram showing a control voltage for controlling a frequency depending on temperature;

[0032] Figure 3 It is shown Figure 1 Parameters of conventional systems in: temperature, frequency and control voltage diagrams;

[0033] Figure 4 is a diagram of an embodiment of the proposed electronic control device;

[0034] Figure 5 is a diagram showing a LC-VCO frequency characteristic curve with control voltage and bias current dependence;

[0035] Figure 6 It is shown Figure 4 Parameters of the proposed method: temperature, frequency and control voltage diagram; and

[0036] Figure 7 is a diagram of the flow of the proposed method.

[0037] Although the various embodiments discussed herein allow for modifications and alternative forms, aspects thereof have been shown by way of example in the accompanying drawings and will be described in detail. However, it should be understood that it is not intended to limit the present disclosure to the specific embodiments described. On the contrary, it is intended to cover all modifications, equivalents, and alternatives that fall within the scope of the present disclosure including the aspects defined in the claims. In addition, the term "example" as used throughout this application is intended to be illustrative only and not limiting. DETAILED DESCRIPTION

[0038] Aspects of the present disclosure are believed to be applicable to a variety of different types of devices, apparatuses, systems and methods involving voltage controlled devices formed as frequency synthesizers. Various aspects may be appreciated through the following discussion of non-limiting examples using an exemplary context, but are not necessarily limited thereto.

[0039] In the following description, various specific details are stated to describe the specific examples presented herein. However, it should be apparent to those skilled in the art that one or more other examples and / or variations of these examples may be practiced without all the specific details given below. In other examples, well-known features are not described in detail so as not to obscure the description of the examples herein. For ease of illustration, the same reference numerals may be used in different drawings to refer to additional instances of the same element or the same element. In addition, although various aspects and features may be described in individual figures in some cases, it should be understood that features from one figure or embodiment may be combined with features of another figure or embodiment, even if the combination is not explicitly shown or explicitly described as a combination.

[0040] Almost every system that relies on a clock signal will use a PLL at some point for frequency synthesis, skew suppression, jitter reduction, or clock recovery. In modern transceiver / receiver systems, a frequency synthesizer implemented as a phase-locked loop (PLL) with an LC-VCO for low noise is required, such as Figure 1 . We see a block diagram of a conventional voltage control device 100 formed as a frequency synthesizer with a main control loop. The frequency synthesizer comprises a phase frequency detector 10 which receives a reference clock signal f ref The signal "up", "down" is provided to the downstream charge pump 20. The charge pump 20 provides the output signal to the loop filter 30, which integrates the input charge from the charge pump 20 and controls the voltage V tune The voltage controlled oscillator 40 (LC-VCO) has a bias current source 41. The voltage controlled oscillator 40 includes variable capacitors (varactors) 42a, 42b which are controlled via a control voltage V tune Being controlled.

[0041] Furthermore, the voltage-controlled oscillator 40 comprises inductors 43a, 43b, transistors 45a, 45b and parasitic resistors 44a, 44b interconnected in a manner known per se. At the output of the voltage-controlled oscillator 40, a voltage having a frequency f is provided. VCO The signal is supplied to the frequency divider element 50, which will have a divided frequency f VCO The signal of is supplied to the second input of the phase frequency detector 10. In this way, the frequency synthesizer is controlled by the main loop with the above components including the charge pump 20 (so-called PLL II type arrangement). Due to the temperature variation and temperature dependence of the components of the LC-VCO, for a given fixed control voltage, the frequency f VCO Will vary depending on temperature.

[0042] Figure 2 An example of a typical LC-VCO frequency tuning curve is depicted, where varactors 42a, 42b are used to control the frequency f of the frequency synthesizer. VCO In general, any type of MOS varactor 42a, 42b may be used, which may only affect the polarity of the frequency gain, which is then taken into account when connecting other blocks of the frequency synthesizer. Due to the progress towards large SoCs in more advanced technology nodes, the on-chip temperature gradients are becoming larger and larger, resulting in a significant amount of temperature induced frequency variation, which is beyond the limit that the control loop of the frequency synthesizer can compensate due to the tuning voltage range limitations. In the worst case scenario, this may produce an unlocked frequency synthesizer, meaning that the self-heating effect is so high that line L (the constant frequency line) is at odds with the frequency synthesizer. Figure 2 There is no longer any intersection between the frequency curves shown in .

[0043] This effect becomes more apparent in the time domain, e.g. Figure 3 Depicted in Figure 3 The assumed time-temperature distribution is shown in (a) of FIG. 1 . For simplicity, the system does not experience any temperature change during startup. At a certain point in time, the system starts to heat up, which causes the VCO output frequency to decrease (e.g. Figure 3 (b)), and the frequency synthesizer adjusts the control voltage V tune To correct for system heating. Figure 3 (b) shows the frequency f for low heating (dashed curve) and high heating (solid curve) VCO For noise reasons, the LC-VCO does have a low VCO gain K VCO , which means that this correction process of the frequency synthesizer only works within a specific temperature range.

[0044] In contrast, Figure 3 (c) shows the transient tuning voltage response of the frequency synthesizer control loop, while Figure 2 shows the control voltage V in the locked mode as the temperature changes and the frequency of the voltage controlled oscillator 40 drifts away from the original calibration temperature (a static voltage shift is required to maintain the locked condition). tune What happens. Eventually, the voltage rail and the charge pump 20 can no longer operate. Therefore, the frequency synthesizer goes out of lock and the application needs to recalibrate the VCO band. If, like in modern advanced technology nodes, the control voltage V tune The smaller the range of , the stronger the effect becomes.

[0045] Since recalibration of the coarse tuning capacitor (if present) in the voltage controlled oscillator 40 during on-line operation is in most cases not possible (as this would produce frequency jumps when switching the capacitor on and off), it is proposed to implement an additional loop-based circuit to compensate for the temperature-induced frequency shift.

[0046] Figure 4 An exemplary voltage-controlled device 100 implemented as a frequency synthesizer is presented, which has a cross-coupled voltage-controlled oscillator 40 and a proposed electronic control device 200, which is based on a bias current adaptation technique implemented with a V2I converter (voltage-to-current converter) 230. With the proposed bias current adaptation technique, it is possible to use the bias current I B (VCO bias current) is used as a second tuning point to control the oscillator frequency via a secondary slow loop inside the frequency synthesizer. As is known, the cross-coupled LC-VCO does have a bias current dependent output frequency f VCOand how the compensation circuit parameters can be calculated in this context. Therefore, no further details are provided in this regard. At the output 48 of the voltage controlled oscillator 40, a voltage having a frequency f is provided. VCO The signal is supplied to the frequency divider element 50, which will have a divided frequency f VCO The signal is provided to a second input of the phase frequency detector 10.

[0047] The two control loops have different time constants, wherein the first control loop has a fast behavior, typically in the microsecond range, wherein the additional control loop has a slow behavior relative to the first loop in order to follow temperature variations (e.g. having a time constant of milliseconds to seconds). In practice, the voltage-controlled frequency synthesizer is controlled by the first control loop and additionally at least partly by means of the proposed electronic control device 200.

[0048] The proposed bias current adaptation technique with the aid of the V2I converter 230 is not limited to analog PLLs (similar to Figure 1 ), but it can also be applied to digital PLLs, where the control voltage Vtune is replaced by a digitized control word, and the voltage-controlled capacitors are replaced by discrete capacitor arrays digitally controlled by the control word.

[0049] The electronic control device 200 comprises three main building blocks or stages. The first stage is a differential amplifier 210 which converts the control voltage V supplied at the first input 201 of the electronic control device 200 and at the second input 47 of the voltage controlled oscillator 40 and dynamically adjusted by the main control loop of the frequency synthesizer. tune For a specific temperature T 0 A reference control voltage V that (eg, initially) calibrates the output frequency of the voltage controlled oscillator 40 tune0 For comparison. Reference control voltage V tune0 It can be regarded as the reference input to the electronic control device 200. In an ideal state, if everything is in a steady state, the control voltage V tune will perfectly converge to the reference control voltage V supplied at the second input 202 of the electronic control device 200 tune0 Downstream of the differential amplifier 210 is a low pass filter 220 which slows down the second control loop being implemented by means of the electronic control device 200. This additional time constant has several reasons.

[0050] First, the second closed control loop should be robust against process variations. In addition, fast tuning voltage changes that are not temperature induced will not be reflected in the VCO bias current I BThe electronic control unit 200 should be as transparent as possible, which means that it should ideally not change the open-loop and closed-loop characteristics of the PLL. Finally, the V2I converter 230 is responsible for converting the temperature-induced tuning voltage change ΔV tune The corresponding bias current change ΔI supplied at the output 203 of the electronic control device 200 and at the first input 46 of the voltage controlled oscillator 40 is converted into B The transconductance G of the V2I converter is calculated as m The possibilities are well known.

[0051] In practice, the electronic control device 200 is configured to control the voltage V tune and V tune0 Minimize the difference between .

[0052] Dynamically adjust the bias current I B The capability of actually prompts the creation of a second control branch for the voltage controlled oscillator 40, which produces a three-dimensional VCO frequency characteristic curve, such as Figure 5 As shown in the example, Figure 5 The LC-VCO frequency characteristic curve with the dependence of tuning voltage and bias current on temperature is shown. The proposed electronic control device 200 utilizes the temperature-induced tuning voltage shift ΔV tune and converts it into a proportional bias current change ΔI B The basic idea is to artificially generate additional VCO gain This can be measured by measuring the tuning voltage shift ΔV tune , converting it to current and feeding this current change to the LC-VCO. From a behavioral perspective, this requires a suitable transconductance G m A voltage-to-current (V2I) converter 230 is provided.

[0053] The required transconductance G of the voltage-to-current converter 230 for the fully temperature compensated voltage-controlled oscillator 40 is m Derived from the two-dimensional frequency curve of the VCO, such as Figure 2 First, we need to extract the maximum frequency shift caused by the VCO over the temperature range:

[0054]

[0055] Full temperature compensation of the voltage control device 100 is not necessary in most cases. Usually, it is sufficient to reduce the sensitivity of the VCO to temperature. Therefore, one can simply The voltage controlled oscillator 40 is set to a value corresponding to the particular temperature range that is desired to be covered without having to recalibrate the voltage controlled oscillator 40 .

[0056] Because a frequency synthesizer formed as a PLL does have a tuning voltage limitation, it should be considered that the tuning voltage can be around the reference voltage V tune0 To what extent the calibrated operating point at changes.

[0057]

[0058] Using equations (1) and (2), the temperature compensated VCO gain can be Calculated as

[0059]

[0060] According to the VCO bias current I resulting in a shifted frequency curve B The change of VCO frequency on bias current I B Using the VCO bias current sensitivity (assuming constant sign for all current sensitivity values) and equation (3), the required transconductance G in the voltage-to-current converter 230 can be derived m To implement the proposed temperature compensation / artificial VCO gain:

[0061]

[0062] Figure 6 The transient curve graphs shown in Figure 2 visually show the overall temperature desensitization of the frequency oscillator when exposed to low and high heating (see Figure 6 The operation in the case of (a)). If the output frequency f of the VCO VCO (See Figure 6 As can be seen from (b) above, the frequency synthesizer can no longer maintain lock without any precautions under strong heating (solid curve). This is due to the tuning voltage limitation of the system ( Figure 6 In contrast, at low heating ( Figure 6 Under the dashed curve in (c), the control voltage V tune The correction is sufficient to obtain locked frequency synthesizer.

[0063] Electronic control 200 provides a sink or source current from the bias current node of the VCO (eg Figure 6 (d)), thereby adjusting the output frequency of the oscillator ( Figure 6 The dotted curve in (b) does not reach the tuning voltage V tune Restrictions ( Figure 6 The dashed curve in (c) provides a locked PLL state.

[0064] In one embodiment, the electronic control device 200 may be configured to maintain the control voltage Vtune With the supply voltage V dd The interdependence.

[0065] In one embodiment, the electronic control device 200 may be configured to control the voltage V tune Relative to the supply voltage V dd Maintain within the specified range.

[0066] Figure 7 The sequence of the proposed method for operating the electronic control device 200 is shown.

[0067] In step 300, a control voltage V of the voltage control device 100 is received. tune and the reference control voltage V tune0 .

[0068] In step 310, the control voltage V tune The bias current is varied by ΔI in such a way that the level remains within the specified range. B Provided to the voltage control device 100.

[0069] The proposed temperature compensation device exploits the properties of a closed loop system in its secondary control loop. The higher the open loop gain of the amplifier used in the differential amplifier stage of the electronic control device 200, the higher the gain that must be achieved by the control voltage V tune The lower the residual error is, the lower the VCO output frequency is controlled to keep it stable.

[0070] The proposed electronic control device 200 can be easily added to an existing PLL without making any changes in the sensitive oscillator core (LC resonant tank). Temperature compensation is done in a closed-loop manner in the secondary slow control loop in order to make it robust against process variations, and at the same time this is not too intrusive from the point of view of the PLL topology, since this is only an additional element to the existing circuit. The original building blocks do not require a specific redesign, and the main loop characteristics are not affected.

[0071] The proposed electronic control device can be used, for example, as part of any LC-VCO based PLL that needs to operate uninterruptedly in the presence of temperature variations that may be too large to be handled by the oscillator tuning voltage alone. For this purpose, UWB ICs are good candidates, but several other ICs, especially in the field of wireless communications, can also benefit from the proposed control device.

[0072] In summary, a temperature desensitization technique for an RF LC-VCO based PLL is proposed by controlling the oscillator bias in a closed loop, which allows the PLL to remain locked over a large temperature range without the need to recalibrate the oscillator.

[0073] As another example, where a specification may refer to a "first" type of structure, a "second" type of structure, the adjectives "first" and "second" are not used to imply any description of the structures or provide any substantive meaning; rather, such adjectives are used merely in conjunction with the English antecedent to distinguish one such similarly named structure from another similarly named structure.

[0074] Based on the above discussion and illustration, it will be readily apparent to those skilled in the art that various modifications and changes may be made to the various embodiments without strictly following the exemplary embodiments and applications shown and described herein. For example, the method illustrated in the figure may involve steps performed in various orders, wherein one or more aspects of the embodiments herein are maintained, or may involve fewer or more steps.

[0075] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Moreover, elements described in connection with different embodiments may be combined. It should also be noted that the reference numerals in the claims should not be interpreted as limiting the scope of the claims.

[0076] It should be noted that the above embodiments have been described with reference to different subject matters. Specifically, some embodiments may have been described with reference to method claims, while other embodiments may have been described with reference to apparatus claims. However, those skilled in the art will appreciate from the above that, unless otherwise indicated, any combination of features relating to different subject matters, in addition to any combination of features belonging to one type of subject matter, in particular a combination of features of a method claim with features of an apparatus claim, is also deemed to be disclosed herein.

[0077] It must be noted that embodiments have been described with reference to different subject matters. Specifically, some embodiments have been described with reference to method claims, while other embodiments have been described with reference to apparatus claims. However, a person skilled in the art will appreciate from the foregoing and the following description that, unless otherwise stated, any combination of features relating to different subject matters, in particular the combination of features of method claims with features of apparatus claims, in addition to any combination of features belonging to one type of subject matter, is also deemed to be disclosed with the present application, in particular the combination of features of method claims with features of apparatus claims.

[0078] Reference numerals:

[0079] 10 Phase frequency detector

[0080] 20 Charge Pump

[0081] 30 Loop filter

[0082] 40 Voltage Controlled Oscillator (VCO)

[0083] 41 Bias current source

[0084] 42a, 42b I-MOS Varactor

[0085] 43a, 43b Inductors

[0086] 44a, 44b parasitic resistor

[0087] 45a, 45b transistors

[0088] 46 1st input

[0089] 47 2nd input

[0090] 48 Output

[0091] 50 Divider Components

[0092] 100 Pressure control device

[0093] 200 Electronic control unit

[0094] 201 1st input

[0095] 202 2nd input

[0096] 203 Output

[0097] 300, 310 Method steps

[0098] f ref Reference frequency

[0099] f VCO Oscillator frequency

[0100] L Line

[0101] ΔI B Bias current change

[0102] I B Bias Current

[0103] V dd Supply voltage

[0104] V tune Control voltage

[0105] V tune0 Reference control voltage.

Claims

1. An electronic control device (200), characterized in that: include: - a control voltage (V tune )'s first input (201); - a reference control voltage (V tune0 )'s second input (202); and - output (203), where The electronic control device (200) is configured to change the bias current (ΔI B ) is provided to the voltage control device (200) so as to adjust the control voltage (V tune ) levels are maintained within the specified range.

2. The electronic control device (200) according to claim 1, characterized in that: The electronic control device (200) is configured to make the control voltage (V tune 、V tune0 ) is minimized.

3. The electronic control device (200) according to claim 1 or 2, characterized in that: The control voltage is implemented in a first control loop of the voltage control device (100), wherein the electronic control device (200) is implemented in an additional control loop of the voltage control device (100).

4. The electronic control device (200) according to claim 3, characterized in that: The control loops have different time constants, wherein the first control loop has a fast behavior to track changes affecting the frequency synthesizer, wherein the additional control loop has a slow behavior in order to follow temperature variations.

5. The electronic control device (200) according to any of the preceding claims, characterized in that The electronic control device (200) is configured to adjust the control voltage (V tune ) to correct the temperature drift of the voltage control device (100).

6. An electronic control device (200) according to any one of the preceding claims, characterized in that The electronic control device (200) is configured to maintain the control voltage (V tune ) and the supply voltage (V dd )’s dependencies.

7. The electronic control device (200) according to claim 6, characterized in that: The electronic control device (200) is configured to tune ) relative to the supply voltage (V dd ) is maintained within the specified range.

8. An electronic control device (200) according to any one of the preceding claims, characterized in that The electronic control device (200) is configured to control a frequency synthesizer based on an LC oscillator.

9. An electronic control device (200) according to any one of the preceding claims, characterized in that The system includes the following blocks which are functionally coupled in series: a differential amplifier (210), a low-pass filter (220), and a voltage-to-current V2I converter (230).

10. A method for operating an electronic control device (200), characterized in that The following steps are involved: - receiving a control voltage (V tune ) and the reference control voltage (V tune0 );as well as - so that the control voltage (V tune ) level within the specified range. B ) is provided to the voltage control device (100).

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