Precision oscillator using imprecision components

Abstract

The present application relates to a precision oscillator using imprecise components and discloses a trimming component within an oscillator comprising: a trimmable current source (Figure 5, trimmable current source component 500) wherein the trimmable current source comprises a trimmable resistor (Figure 5, RDAC component 510) and a trimmable current component (Figure 5, trimmable current component 520); a comparator (FIG. 1, comparator 108) comprising a first input terminal coupled to a trimmable current source (FIG. 1, current source component 102) and a second input terminal coupled to a reference voltage source; a switch coupled to the first input terminal and a trimmable current source (Figure 1, switch 112 or switch 114); and a dressable capacitor (Fig. 1, capacitor component 104 or capacitor component 106) coupled to a switch, where the switch is coupled between the dressable capacitor and the dressable current source.

Description

[0001] This application is a divisional application of Chinese patent application 201811569465.3, whose application date is December 21, 2018 and whose name is “Precision Oscillator Using Imprecise Components”. Background Art

[0002] An oscillator is an electronic device that generates a periodic output signal (such as a sine wave, square wave, or triangle wave). In order to generate an oscillating output signal, an oscillator often converts a direct current (DC) received from a power supply into an alternating current (AC) signal. By utilizing the output signal of an oscillator, circuit designers can use oscillators for a variety of electronic systems, ranging from clock generation of control logic components (e.g., microprocessors), transmission of signals for transmitter devices, generation of audio sounds, and implementation of carrier synthesis in cellular technology. Depending on the application, oscillators can exhibit different topologies and performance parameters. As an example, a circuit designer can use a low-frequency oscillator (e.g., about 20 hertz (Hz)) in an audio synthesis application, while a radio frequency (RF) oscillator generates an output signal in a frequency range of about 100 kilohertz (kHz) to 100 gigahertz (GHz).

[0003] In certain applications that require a relatively high precision and stable output signal, circuit designers may prefer an external oscillator to an internal oscillator. Internal oscillators, also known as zero-pin oscillators, are generally less precise due to the device's sensitivity to noise and / or temperature variations. The imprecision disadvantages of internal oscillators may stem from manufacturing techniques and process variations. For example, manufacturers may use polysilicon materials to manufacture components within an internal oscillator, such as polysilicon resistor components. Unfortunately, due to the characteristics of polysilicon materials, polysilicon-based components may have a relatively high temperature coefficient (e.g., about 2500 parts per million (ppm) per degree Celsius (°C) for polysilicon resistor components) that affects the properties of the component as the operating temperature changes. Although manufacturers can use other types of components with lower temperature systems (such as silicide polysilicon resistor components (e.g., about 100ppm / °C-200ppm / °C)) or zero temperature coefficient of resistance (ZTCR) components (e.g., less than 50ppm / °C), the cost of preparing internal oscillators with more precise components generally tends to be more expensive. Therefore, being able to improve the accuracy of an internal oscillator without increasing the fabrication cost remains valuable in fabricating precision oscillators. Summary of the invention

[0004] A simplified overview of the disclosed subject matter is presented below to provide a basic understanding of some aspects of the subject matter disclosed herein. This overview is not an exhaustive introduction to the technology disclosed herein. This overview is not intended to identify key or important elements of the present invention, or to delineate the scope of the present invention. The sole purpose of this overview is to present some concepts in a simplified form as a prelude to a more detailed description discussed later.

[0005] In one embodiment, an oscillator includes: a trimmable current source, wherein the trimmable current source includes a trimmable resistor and a trimmable current component; a comparator, the comparator including a first input terminal coupled to the trimmable current source and a second input terminal coupled to a reference voltage source; a switch, the switch coupled to the first input terminal and the trimmable current source; and a trimmable capacitor, the trimmable capacitor coupled to the switch, wherein the switch is coupled between the trimmable capacitor and the trimmable current source.

[0006] In another embodiment, an oscillator includes: a trimmable current source, the trimmable current source being configured to: trim one or more resistance values ​​that affect a first portion of a capacitor charging current generated from the trimmable current source; and trim the first portion of the current to adjust a proportion of the first portion of the current in the capacitor charging current generated from the trimmable current source; a comparator, the comparator including a first input terminal coupled to the trimmable current source and a second input terminal coupled to a reference voltage source; and a trimmable capacitor, the trimmable capacitor being coupled to the first input terminal, wherein the trimmable capacitor is configured to implement capacitor switching that controls a charging time of the trimmable capacitor.

[0007] In yet another embodiment, a method includes: trimming, for a relaxation oscillator, one or more resistance values ​​that affect a first portion of a current of a capacitor charging current generated from a trimmable current source within the relaxation oscillator; trimming, for the relaxation oscillator, the first portion of the current to adjust a proportion of the first portion of the current in the capacitor charging current generated from the trimmable current source, wherein the capacitor charging current is a combination of the first portion of the current and a second portion of the current; and trimming, for the relaxation oscillator, a trimmable capacitor to implement capacitor switching that controls a charging time of the trimmable capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a detailed description of various examples, reference will now be made to the accompanying drawings, in which:

[0009] Figure 1 is a block diagram of an oscillator according to various embodiments.

[0010] Figure 2 Shown to provide corresponding to Figure 1 The waveform diagram of the operation of the oscillator is shown in the waveform diagram.

[0011] Figure 3 is a schematic diagram of another oscillator according to various embodiments.

[0012] Figure 4 Shown includes corresponding to Figure 3The waveform diagram of the operation of the oscillator is shown in the waveform diagram.

[0013] Figure 5 is a schematic diagram of an embodiment of a trimmable current source component configured to perform resistance value trimming and temperature slope trimming.

[0014] Figure 6 is a schematic diagram of an embodiment of a trimmable current source configured to perform temperature slope trimming to additionally tune a capacitor charging current Ic.

[0015] Figure 7 is a schematic diagram of another embodiment of a trimmable current source configured to perform temperature slope trimming to additionally tune the capacitor charging current Ic.

[0016] Figure 8 is a schematic diagram of an embodiment of a trimmable capacitor component.

[0017] Fig. 9 is a flow chart of an embodiment of a method for trimming multiple components within a precision oscillator to stabilize and achieve a target frequency.

[0018] Although certain embodiments will be described in conjunction with the illustrative embodiments shown herein, the present invention is not limited to those embodiments. On the contrary, all alternatives, modifications and equivalents are included in the spirit and scope of the present invention as defined by the claims. In the drawings that are not drawn to scale, the same reference numerals are used throughout the description and in the drawings for parts and elements having the same structure, and primed reference numerals are used for parts and elements whose function and construction are similar to those parts and elements having the same non-primed reference numerals. DETAILED DESCRIPTION

[0019] Certain terms have been used throughout this description and claims to refer to specific system components. As will be appreciated by those skilled in the art, different subjects may refer to components by different names. This document is not intended to distinguish components that have different names but the same functions. In this disclosure and claims, the terms "include" and "comprise" are used in an open manner, and should therefore be interpreted as meaning "including but not limited to ...". Also, the term "coupled" or "coupled" is intended to mean an indirect or direct wired or wireless connection. Therefore, if a first device is coupled to a second device, the connection may be by direct connection or by indirect connection via other devices and connections. Detailed description "based on" is intended to mean "based at least in part". Therefore, if X is based on Y, X can be a function of Y and any number of other factors. Unless explicitly defined, the terms "one", "an" and "the" are not intended to refer to singular entities, but to include general categories that can be used for specific examples of illustration. The use of the terms "one", "an" can therefore mean any number of at least one, including "one", "one or more", "at least one" and "one or more than one". The term "or" means any one of the alternatives and any combination of the alternatives including all of them, unless the alternatives are expressly indicated as mutually exclusive. The phrase "at least one of" when combined with a list of items means a single item from the list or any combination of the items in the list. The phrase does not require all of the listed items, unless expressly defined.

[0020] The above discussion is not meant to illustrate the principles and various embodiments of the present invention. Once the above disclosure is fully understood, multiple changes and modifications will become apparent to those skilled in the art. It is intended that the appended claims be interpreted as covering all such changes and modifications.

[0021] As used herein, the term "imprecision component" refers to a component having the following properties: a variation of greater than ±50% around a nominal process inflection point, a temperature coefficient variation of greater than 500ppm / °C, a nominal temperature coefficient of greater than 1000ppm / °C, or any combination thereof. Imprecision components within an oscillator can allow the accuracy of the oscillator to exceed ±1% over process, voltage, and temperature (PVT). An example of an imprecision component is a polysilicon resistor component, which can have a nominal temperature coefficient of approximately 2500ppm / °C, which can vary from 1500ppm / °C to 3300ppm / °C during the manufacturing process. Also used herein, the term "precision component" refers to a component having the following properties: a variation of less than ±20% around a nominal process inflection point, a temperature coefficient of less than 200ppm / °C, or both. Precision components within an oscillator can allow the accuracy of the oscillator to be equal to or less than ±1% over PVT. Examples of precision components are silicide polysilicon resistor components, which may have a temperature coefficient of approximately 100-200 ppm / °C, or zero temperature coefficient of resistance (ZTCR) components, which may have a temperature coefficient of less than approximately 50 ppm / °C.

[0022] Various example embodiments are disclosed herein to reduce operational variations of an internal oscillator that does not include precision components. In one or more embodiments, the internal oscillator is a relaxation oscillator that includes one or more comparators and at least one current source that charges a plurality of capacitors. The comparator is disposed to compare the capacitor voltage with one or more reference voltages to generate one or more periodic output signals. In order to manage the variability effects of including imprecise components such as polysilicon resistor components, the internal oscillator is capable of performing trimming operations for at least some of the imprecise components. As an example, the internal oscillator can perform trimming operations with a digital to analog circuit (DAC) such as a resistor DAC (RDAC), a current DAC (IDAC), and a capacitor DAC (CDAC). The internal oscillator includes an RDAC to trim and correct the resistance value of the polysilicon resistor component. In order to further improve accuracy, the IDAC performs temperature slope trimming to adjust a first portion of the current of the charging current supplied to the capacitor. Specifically, the temperature slope trimming can be based on correcting the resistor ratio of the polysilicon resistor component. After temperature slope trimming is completed, one or more CDACs may trim the charge capacitor to correct for any remaining variability or errors caused by process and / or temperature variations.

[0023] Figure 1 is a block diagram of an oscillator 100 according to various embodiments. Figure 1, oscillator 100 is a non-crystal based oscillator including a current source component 102, a capacitor component 104 and a capacitor component 106, a comparator 108 and a data (D) flip-flop 110. Capacitor component 104 and capacitor component 106 can be coupled to a non-inverting terminal of comparator 108 depending on whether switch 112 and switch 114 are in a closed position or an open position. To generate an input voltage signal Vc at the non-inverting terminal of comparator 108, current source component 102 is also coupled to the non-inverting input terminal of comparator 108 and charges capacitor component 104 or capacitor component 106 depending on the position of switch 112 and switch 114. Capacitor component 104 and capacitor component 106 are also connected to switch 116 and switch 118 to allow capacitor component 104 and capacitor component 106 to discharge by connecting them to a ground reference. Comparator 108 includes a supply reference voltage Vc coupled to the comparator 108. REF Reference power circuit ( Figure 1 The output of comparator 108 is coupled to the clock (CK) input of D flip-flop 110 to generate the output terminals of D flip-flop 110 labeled φ and The output signal φ represents the positive voltage half cycle of the output signal of the oscillator 100, and the output signal Represents the negative voltage half cycle of the output signal of the oscillator 100. Output signal Connected to the data input terminal of the D flip-flop 100 to form a feedback loop.

[0024] like Figure 1 As shown, the oscillator 100 is a relaxation oscillator, which performs current capacitor charging to generate a capacitor voltage Vc, and compares the capacitor voltage Vc with a reference voltage V REF Switches 112, 114, 116, and 118 are dependent on whether oscillator 110 generates a positive voltage half cycle (eg, a high output signal φ) or a negative half cycle (eg, a high output signal φ). ) is in an open or closed state as the output signal of the oscillator 100. When the oscillator 100 generates a positive voltage half cycle, the switches 112 and 118 are in a closed position, while the switches 114 and 116 are in an open position. During the positive voltage half cycle, the current source component 102 supplies current to the capacitor component 104 via the switch 112 to generate the capacitor voltage Vc. The capacitor voltage Vc continues to increase until the capacitor voltage Vc meets and / or exceeds the voltage V REF Closing switch 118 discharges any charge stored by capacitor component 106 by connecting the switch to the ground reference.

[0025] At the negative voltage half cycle, switch 114 and switch 116 are in the closed position, while switch 112 and switch 118 are in the open position. Current source component 102 provides current to capacitor component 106 to generate capacitor voltage Vc. Since capacitor component 106 is discharged during the positive voltage half cycle, capacitor component 106 initially provides a relatively low capacitor voltage Vc (e.g., 0 volts). When current source component 102 charges capacitor component 106 via switch 114, capacitor voltage Vc increases. At the same time, capacitor component 104 discharges any stored charge by closing switch 116 and connecting capacitor component 104 to the ground reference.

[0026] Figure 2 Shown to provide corresponding to Figure 1 200 of waveform graphs 202, 204, and 206 of the operation of the oscillator 100 shown in FIG. Figure 1 , waveform graph 202 plots the capacitor voltage Vc at the non-inverting terminal of capacitor 108 over a period of time; waveform graph 204 plots the output signal φ associated with a positive voltage half-cycle generated at D flip-flop 110 over the same period of time; and waveform graph 206 plots the output signal φ associated with a negative voltage half-cycle generated at D flip-flop 110 over the same period of time. Whenever the capacitor voltage Vc reaches and / or exceeds the reference voltage V REF When the voltage of , the comparator applies a pulse causing the D flip-flop 110 to change state.

[0027] As shown in waveform graph 202, capacitor voltage Vc has a repeating pattern similar to a sawtooth waveform or an asymmetrical triangular waveform. At sawtooth wave 208, switch 112 and switch 118 are in a closed position to generate a positive voltage half-cycle wave 216. The voltage increase of Vc at sawtooth wave 208 indicates that capacitor component 104 is charged by current source component 102. The slope of sawtooth wave 208, which indicates the charging rate of capacitor component 104, depends on the capacitor charging current Ic and the capacitance of capacitor component 104. As described above with reference to Figure 1 As discussed, when the current source component 102 charges the capacitor component 104 , the capacitor component 106 is discharged by closing the switch 118 and opening the switch 114 .

[0028] For the sawtooth wave 210, the switches 114 and 116 are in the closed position to generate the negative voltage half-cycle wave 220. The drop in voltage Vc shown in the sawtooth wave 210 corresponds to transitioning the switches 114 and 116 to the closed position and transitioning the switches 112 and 118 to the open position. Previously, the capacitor component 106 was discharged to a relatively low voltage (e.g., approximately 0 volts), causing the voltage Vc to drop at the beginning of the sawtooth wave 210. Once the switches 112, 114, 116, and 118 are in their updated positions, the current source component 102 then charges the capacitor component 106; thereby, increasing the voltage Vc supplied to the comparator 108. Charging the capacitor component 106 to increase the voltage Vc produces the negative voltage half-cycle wave 220. The slope of the sawtooth wave 210, which represents the charging rate of the capacitor component 106, depends on the capacitor charging current Ic and the capacitance of the capacitor component 106. As shown in waveform graphs 202, 204, and 206, sawtooth waves 208 and 210 continue to repeat in the same manner over the remaining time period to continue to generate output signals φ and φ.

[0029] A precision oscillator generally produces a relatively high precision and stable output signal, such as one that allows the output signal to be set to a precise and stable frequency. Figure 1 , the output signal φ of the oscillator 100 and the output signal The frequency of oscillator 100 may vary depending on the temperature coefficient of the resistance value associated with current source component 102. In particular, the output frequency of oscillator 100 is based on the capacitor charging current Ic supplied by current source component 102, the capacitance values ​​of capacitor components 104 and 106, and the reference voltage V supplied at the inverting terminal of comparator 108. REF Equation 1 presented below specifically defines the frequency value of the oscillator 100 as:

[0030]

[0031] In Equation 1, F out represents the output frequency of the oscillator 100, which is related to the output signal φ and the output signal Ic represents the capacitor charging current supplied by the current source component 102; C represents the charging capacitance value corresponding to one of the charging capacitor component 104 and the charging capacitor component 106; and V REF represents the reference voltage supplied at the inverting terminal of the comparator 108. The current source component 102 supplies a capacitor charging current Ic, which is proportional to the reference voltage V REF and the resistance value of the current source component 102 determine the capacitor charging current Ic. Equation 2 presented below defines the capacitor charging current Ic as:

[0032]

[0033] In Equation 2, Ic represents the capacitor charging current supplied by the current source component 102; V REF represents a reference voltage supplied at the inverting terminal of the comparator 108; and R represents a resistance value of the current source part 102. According to Equation 2, Equation 1 can be rewritten as shown in Equation 3.

[0034]

[0035] As shown in Equation 3, the output frequency of oscillator 100 is based on the resistance value of current source component 102 and the capacitance value of corresponding charging capacitor component 104 or charging capacitor component 106. Due to this dependence, the temperature coefficient of the resistance of current source component 102 may affect the temperature coefficient of the output frequency of oscillator 100.

[0036] In one or more embodiments, the current source component 102 may include one or more imprecision resistor components that cause the frequency or time period of the oscillator 100 to have relatively large variations. For example, the resistance value of the current source component 102 may be based on a polysilicon resistor component, which may depend on the operating temperature and temperature coefficient at the process inflection point of the device, potentially causing a resistance value variation of about ±30%, and causing a variation of about -60% to about +90% around the nominal process inflection point. The oscillator 100 may also be affected by variations from other components (such as capacitor components 104 and capacitor components 106 and comparator 108). As an example, capacitor 104 and / or capacitor 106 may have a capacitance variation of about ±20%, and comparator 108 may have a variation of about ±5% caused by comparator delay and other margins. Due to process variations from one or more imprecision components, the time period and frequency of the oscillator 100 may vary from about -80% to about +200% overall. In other words, oscillator 100 can have a minimum to maximum variation in output frequency of approximately 13 times.

[0037] To reduce the effects of process and temperature variations associated with fabricating current source component 102, current source component 102 and capacitor components 104 and 106 may be configured as trimmable components. In one or more implementations, current source component 102 is capable of performing resistor trimming that compensates for process variations of one or more imprecise resistor components (e.g., polysilicon resistor components). As an example, current source component 102 may correct a resistor defined as V by utilizing a trimmable resistor component (such as RDAC). REF / R, the first current part of the capacitor charging current Ic. Figure 5Further details on resistor trimming are provided in the following. In addition, the current source component 102 can implement temperature slope trimming to further tune the capacitor charging current Ic. The current source component 102 can utilize a trimmable current component (such as an IDAC) to implement a voltage defined as V PTAT / R, and the second current portion is generated according to a PTAT (proportional to absolute temperature) voltage to generate a target capacitor charging current Ic. Figure 6 More details on temperature slope trimming are provided. To further improve the precision (e.g., accurate and stable frequency) of oscillator 100, capacitor component 104 and capacitor component 106 can utilize capacitor trimmable components that perform capacitor trimming to tune the capacitance value. For example, each capacitor component 104 and capacitor component 106 can include a CDAC to adjust the capacitance value to obtain a target frequency of oscillator 100. Figure 7 More details are provided for capacitor trimming.

[0038] Figure 3 is a schematic diagram of another oscillator 300 according to various embodiments. Figure 1 Compared to the oscillator 100 shown in FIG. 1 , the oscillator 300 is a non-crystal-based relaxation oscillator including a current source component 102 that provides a charging current to a capacitor component 104 and a capacitor component 106. In other words, the oscillator 300 includes imprecise components that are sensitive to temperature and process variations. The oscillator 300 differs from the oscillator 100 in that the oscillator 300 includes two comparators 302 and 304 and a set-reset (SR) latch 306. Figure 3 As shown, the inverting terminals of comparator 302 and comparator 304 receive input voltage V REF The non-inverting terminals of the comparator 302 and the comparator 304 are each connected to one of the capacitor 104 and the capacitor 106, and are connected to the current source component 102 depending on whether the switch 112 and the switch 114 are open or closed. As an example, when the switch 112 is in the closed position and the switch 114 is in the open position, the non-inverting terminal of the comparator 302 is connected to the current source component 102 and the capacitor component 104. In another example, when the switch 114 is in the closed position and the switch 112 is in the open position, the non-inverting terminal of the comparator 304 is connected to the current source component 102 and the capacitor component 106. The output of the comparator 302 is connected to the reset input terminal of the SR latch 306, and the output of the comparator 304 is connected to the set input terminal of the SR latch 306. Based on the received input, the SR latch 306 generates the output signal φ and the output signal φ.

[0039] Figure 4A waveform graph 400 is shown including a waveform graph 402, a waveform graph 404, and a waveform graph 406 corresponding to the operation of the oscillator 300. The waveform graph 402 plots the output signal φ associated with a positive voltage half-cycle generated at the Q output terminal of the SR latch 306 over a period of time; the waveform graph 404 plots the output signal φ associated with the positive voltage half-cycle generated at the Q output terminal of the SR latch 306 over a period of time; The output signal associated with the negative voltage half cycle generated at the output terminal The waveform graph 406 plots the capacitor voltage X ( Figure 3 and waveform 408 and the capacitor voltage Y ( Figure 3 shown in ).

[0040] As shown in waveform graphs 402 and 404, capacitor voltage X starts at a relatively low voltage (eg, 0 volts) and capacitor voltage Y generates sawtooth waveform 416. When capacitor voltage Y meets and / or exceeds reference voltage V REF When , comparator 304 applies a pulse to SR latch 306 and causes SR latch 306 to change state. Subsequently, capacitor voltage X transitions to sawtooth wave 414, and capacitor voltage Y transitions to a relatively low voltage. Similar to capacitor voltage Y, when capacitor voltage X meets and / or exceeds reference voltage V REF , comparator 302 pulses SR latch 306 and causes SR latch 306 to change state. At sawtooth wave 414, switch 112 and switch 118 are in a closed position, and switch 114 and switch 116 are in an open position to generate a positive voltage half-cycle wave. At sawtooth wave 416, switch 112 and switch 118 are in an open position, and switch 114 and switch 116 are in a closed position to generate a negative voltage half-cycle wave.

[0041] Return to reference Figure 3In order to reduce the impact of process and temperature variations associated with preparing the current source component 102, the oscillator 300 is capable of performing trimming operations at the current source component 102 and the capacitor components 104 and 106. Instead of utilizing a single amplitude trimming circuit to trim the frequency of the oscillator 300 within an accuracy of ±1%, the oscillator 300 may implement a trimming circuit that trims multiple components within the oscillator 300. The current source component 102 includes a trimmable resistor component that can be trimmed to compensate for process variations of one or more imprecise resistor components (e.g., a polysilicon resistor component). In addition, the current source component 102 includes a trimmable current component that performs temperature slope trimming to further tune the capacitor charging current Ic by compensating for temperature coefficient variations. In order to improve the precision and stability of the oscillator 300, the capacitor component 104 and the capacitor component 106 may also include a trimmable capacitor component that tunes the capacitance value. Reference Figure 5-Figure 7 , where the different trimming operations are discussed in more detail.

[0042] Although Figure 1 and Figure 3 Specific embodiments of the oscillator 100 and the oscillator 300 are shown, but the disclosed trimming operation is not limited to Figure 1 and Figure 3 For example, various different types of electrical switches, such as field effect transistors (FETs), may be used to implement Figure 1 and Figure 3 114, switch 116, and switch 18 within. Examples of FETs include, but are not limited to, enhanced n-channel metal oxide semiconductor field effect (NMOS) transistors, other types of NMOS transistors, n-type junction gate field effect transistors (NJFETs), and bipolar junction transistors (BJTs) (e.g., NPN transistors). In addition, the relaxation oscillator may employ another flip-flop type component, a latch type component, or some other type of electrical circuit configured to store state information and generate a plurality of stable states, rather than utilizing a D flip-flop or an SR latch. Figure 1 and Figure 3 The use and discussion of are merely examples for ease of description and explanation.

[0043] Figure 5is a schematic diagram of an embodiment of a trimmable current source component 500 configured to perform resistance value trimming and temperature slope trimming. As previously discussed, the trimmable current source component 500 can be fabricated using fabrication and / or process techniques that create imprecise components with relatively large temperature coefficients (which in turn cause capacitor charging current Ic to vary based on temperature). To compensate for relatively large process variations and temperature coefficients, the trimmable current source component 500 can perform resistance value trimming using RDAC components 504 and RDAC components 510, and perform temperature slope trimming using a trimmable current component 520 as part of a bias circuit 519. In FIG. Figure 6 Temperature slope trimming with a trimmable current component 520 (such as an IDAC component that compensates for temperature coefficient variations) is discussed in more detail in . The RDAC component 504 and the RDAC component 510 may be trimmed together to obtain a target resistance value to account for process variations.

[0044] exist Figure 5 , RDAC component 504 has one end connected to the inverting terminal of amplifier 502 and an opposite end connected to the non-inverting terminal of amplifier 506. The end of RDAC component 504 connected to the inverting terminal of amplifier 502 is also connected to the source node of transistor 522. RDAC component 510 has one end connected to the inverting terminal of amplifier 508 and the source node of transistor 525. The opposite end of RDAC component 510 is connected to the ground reference. Constant voltage V CON represents the voltage supplied to the inverting terminal of the amplifier 508 , and also represents the voltage drop across the RDAC component 510 .

[0045] In one or more embodiments, RDAC component 504 and RDAC component 510 are imprecise components (e.g., polysilicon resistor components) with relatively large process variations. RDAC component 504 and RDAC component 510 are configured to adjust their resistance values ​​to offset the relatively large process variations associated with each component. In one or more embodiments, RDAC component 504 and RDAC component 510 may be polysilicon resistor components with process variations ranging from -60% to +90%. Figure 5 As shown, due to the first current portion I of the charging current Ic CON Equal to V CON / R RDAC , so any resistance change in the RDAC component 510 affects the generated first current portion I CON To compensate for the varying resistance value caused by process variations, the RDAC component 510 is trimmed to the resistance value R RDAC , correct the first current part I CONThe trimmable current source component 500 can trim the RDAC component 504 and the RDAC component 510 to a resistance value R within a desired accuracy range (eg, within 5%-6% accuracy) of a target resistance value at a specified temperature (eg, room temperature). RDAC As an example, due to process variations, when the target resistance value is set to 1.00 kilo-ohms, the RDAC component 510 may have a resistance value of 1.20 kilo-ohms at room temperature. The RDAC component 510 performs resistor trimming to reduce the actual resistance value R RDAC Reduced to less than or equal to 1.05 kOhm. Figure 5 The RDAC component 504 is also shown to implement similar resistor trimming to have a resistance value R RDAC Matched resistor values.

[0046] In order to determine whether the resistance values ​​of the RDAC components 504 and 510 have drifted away from the target resistance value R RDAC , the trimmable current source component 500 includes a trimming system 514 and a resistor trimming control 512. The trimming system 514 includes measuring a first current portion I at a specified temperature (eg, room temperature) CON To measure the first current portion I CON , the resistor trimming control 512 sets the switch 518 to a closed state to allow current to flow to the current measuring component 516. When the switch 518 is in the closed state, the transistor 532 converts the first portion of the current I CON The mirrored first partial current I CON The trim system 514 determines the offset between the measured resistance value and the target resistance value of the RDAC component 510 based on the measured current. The trim system 514 then converts the resistance offset into a resistor trim bit to supply to the resistor trim control 512. The resistor trim control 512 uses the resistor trim bit to adjust the resistance value of the RDAC component 510 to be closer to the target resistance value. The resistor trim control 512 also adjusts the resistance value of the RDAC component 504 to the target resistance value based on the measured current.

[0047] In one or more implementations, to adjust the resistance value, each of the RDAC component 504 and the RDAC component 510 may include a plurality of switches 528 that set which resistors 526 are connected in series to the fixed resistor 530. Figure 5 In the embodiment, each resistor 526 is set to have the same resistance value ΔR to change the fixed resistance value R FIXIn other embodiments, each resistor 526 may be set to a different resistance value (such as ΔR, Δ2R, and / or Δ4R) to increase the resistance of RDAC component 504 and RDAC component 510. Based on the resistor trimming bit, resistor trim control 512 sets switch 528 to an open position or a closed position. For example, resistor trim control 512 may receive an indication that only resistors with resistance value R FIX The fixed resistor 530 should be connected to the inverting terminal of the amplifier 508. In another example, the resistor trim control 512 may receive a resistor trim bit indicating that two of the resistors 526 should be connected in series to the fixed resistor 530 to get closer to the target resistance value.

[0048] Figure 6 is a schematic diagram of an embodiment of a trimmable current source 600 configured to perform temperature slope trimming to compensate for temperature variations associated with generating a capacitor charging current Ic. As previously mentioned in Equation 1, the frequency of the oscillator depends on the capacitor charging current Ic. Increasing the capacitor charging current Ic increases the frequency of the oscillator. In particular, referring to Figure 2 Increasing the capacitor charging current Ic increases the slope of sawtooth wave 208 and sawtooth wave 210, which allows the capacitor voltage Vc to equal and / or exceed the reference voltage V in a shorter time frame. REF Conversely, reducing the capacitor charging current Ic will reduce the frequency of the oscillator, which reduces the slope of sawtooth wave 208 and sawtooth wave 210. Once the trimmable current source 600 trims the RDAC component 504 and the RDAC component 510 to compensate for the process variation of the components, the trimmable current source 600 obtains V CON and V PTAT to reduce temperature variations and produce the target capacitor charging current Ic.

[0049] The capacitor charging current Ic is proportional to the current I CON and current I PTAT Equation 4 presented below defines the capacitor charging current Ic.

[0050]

[0051] In Equation 4, β represents the slope trimming coefficient; Ic represents the capacitor charging current supplied by the current source component 102; V CON represents the voltage received at the amplifier 508 and the voltage drop across the RDAC component 510; V PTAT represents the voltage drop across the RDAC component 504; and R RDACrepresents the trimmed resistance value of RDAC component 504 and RDAC component 510. With respect to β in Equation 4, when the slope trim code changes, β will also change in order to manipulate the overall slope of the frequency. Based on Equation 4, the capacitor charging current Ic is the current I PTAT and proportional to the current I CON The sum of .

[0052] From Equation 4, Equation 1 can be rewritten as shown in Equation 5 and Equation 6 to determine the frequency of the oscillator.

[0053]

[0054] In Equation 5 and Equation 6, F out represents the output frequency of the oscillator; Ic represents the capacitor charging current supplied by the current source component 102; V CON represents the constant voltage received at the amplifier 508 and the voltage drop across the RDAC component 510; V PTAT represents the voltage drop across the RDAC component 504; R RDAC represents the trimmed resistance value of the RDAC component 504 and the RDAC component 510; V REF represents a reference voltage supplied to the comparator; and C represents a corresponding charging capacitor component (e.g., Figure 1 and Figure 3 Based on Equation 6, V CON and V PTAT The ratio affects the output frequency of the oscillator.

[0055] The PTAT current can be easily obtained from the band gap and / or can be derived from the PTAT voltage obtained from the band gap. Figure 6 In this example, a single bandgap circuit is used to generate a constant voltage V CON and two voltages V BG and voltage V BE . Recall the constant voltage V CON is supplied to the non-inverting terminal of the amplifier 508. The voltage V BG is supplied to the non-inverting terminal of the amplifier 502, and the voltage V BE is supplied to the inverting terminal of the amplifier 506. The voltage V CON and voltage V BG has a constant voltage, and the voltage V BE It has a negative slope with temperature. Voltage V PTAT Equal to voltage V BG and voltage V BEThe accuracy of the bandgap voltage depends on the resistor ratio rather than the absolute resistance value, and thus, the resistors used in the bandgap design can be imprecise components (e.g., for R RDAC Component 504 and R RDAC The same type of resistor in component 510 is used without requiring a precision circuit with a precision resistor. Figure 6 As shown, a complementary to absolute temperature (CTAT) circuit that decreases in proportion to temperature is not used to generate the target capacitor charging current Ic.

[0056] The trimmable current source 600 utilizes the trimmable current component 520 to implement temperature slope trimming that reduces the temperature coefficient of the frequency of the oscillator. As an example, the trimmable current component 520 may be an IDAC that corrects the voltage V CON and voltage V PTAT The ratio of 200V to 200V is used to obtain the target capacitor charging current Ic which helps to achieve a precise and stable oscillator frequency. Figure 6 In the embodiment, the trimmable current component 520 is configured to modify the current I by digital control. CON In embodiments where the trimmable current code is used for the IDAC, the trimmable current source 600 can adjust the trimmable current code (eg, the IDAC code) to tune the IDAC to increase or decrease the proportional current I CON . Increase the current I CON The overall temperature slope of the oscillator frequency is reduced by a factor of CON The overall temperature slope of the oscillator frequency will increase in proportion to the Figure 6 As shown, in order to increase or decrease the current I CON , the trimmable current component 520 acts as a current mirror that enables one or more of the transistors 604 to obtain the desired first partial current I CON The switch 606 is used to enable the transistor 604 within the trimmable current component 520 by setting the switch to an open state or a closed state based on the trimmable current code.

[0057] Figure 7 FIG. 7 shows a trimmable current source 700 utilizing a trimmable current component 720 to implement temperature slope trimming that reduces the temperature coefficient of the frequency of the oscillator. Figure 6 , the trimmable current component 720 may be an IDAC, and the IDAC correction voltage V CON and voltage V PTAT ratio to obtain the target capacitor charging current Ic which helps to achieve a precise and stable oscillator frequency. Figure 6 The trimmable current component 720 is configured to modify the current I by digital control PTATIn embodiments where the trimmable current code is an IDAC, the trimmable current source 700 may adjust the trimmable current code (eg, the IDAC code) to tune the IDAC to increase or decrease the proportional current I PTAT . Increase the current I PTAT The overall temperature slope of the oscillator frequency is increased by a factor of 1. PTAT The ratio of will reduce the overall temperature slope of the oscillator frequency. Figure 7 As shown, in order to increase or decrease the current I PTAT The trimmable current component 720 acts as a current mirror that enables one or more of the transistors 704 to obtain the desired second partial current I PTAT The switch 606 is used to enable the transistor 704 within the trimmable current component 720 by setting the switch to an open state or a closed state based on the trimmable current code.

[0058] Figure 8 is a schematic diagram of an embodiment of a trimmable capacitor component 804 and a trimmable capacitor component 806. Figure 1 As an example, trimmable capacitor component 804 and trimmable capacitor component 806 correspond to or are a portion of capacitor component 104 and capacitor component 106, respectively. After performing temperature slope trimming, trimmable capacitor component 804 and trimmable capacitor component 806 may be used to correct the remaining amplitude error for achieving the target output frequency of the oscillator. Recall that Figure 6 In the embodiment, the trimmable current source 600 performs temperature slope trimming. When temperature slope trimming is performed to correct the temperature slope of the frequency of the oscillator, the first proportional current I CON The increase in the frequency amplitude of the oscillator tends to increase and reduce the first proportional current I CON The increase and decrease in frequency amplitude may cause a residual amplitude error in the frequency, which may be corrected using trimmable capacitor component 804 and trimmable capacitor component 806 .

[0059] In one or more implementations, each of the trimmable capacitor component 804 and the trimmable capacitor component 806 is a CDAC that trims the charge capacitor. Figure 8 As an example, the trimmable capacitor component 804 and the trimmable capacitor component 806 include two 10-bit split CDAC arrays, wherein the two 10-bit split CDAC arrays are identical to each other and utilize the same 10-bit trimming code to adjust the capacitor charging time. The trimmable capacitor component 804 and the trimmable capacitor component 806 are both configured to include a fixed capacitance C fix808 is connected in parallel with a capacitor 830 having a capacitance C. Capacitor 832 is connected in series to capacitor 808 and capacitor 830 and has a capacitance of 32C / 31. The two 10-bit split CDAC arrays include capacitor 810, capacitor 812, capacitor 814, capacitor 816, capacitor 818, capacitor 820, capacitor 822, capacitor 824, capacitor 826, and capacitor 828 having capacitances of 16C, 8C, 4C, 2C, C, 16C, 8C, 4C, 2C, and C, respectively. Other embodiments of the 10-bit split CDAC array may be configured to assign different capacitance values ​​to capacitor 810, capacitor 812, capacitor 814, capacitor 816, capacitor 818, capacitor 820, capacitor 822, capacitor 824, capacitor 826, and capacitor 828.

[0060] Figure 8 The trimmable capacitor component 804 and the trimmable capacitor component 806 are shown using a capacitor having a position b 9:0 The 10-bit trimming code implements capacitor switching of capacitor 810, capacitor 812, capacitor 814, capacitor 816, capacitor 818, capacitor 820, capacitor 822, capacitor 824, capacitor 826, and capacitor 828. Figure 8 As shown, capacitor 810, capacitor 812, capacitor 814, and capacitor 816 are the portion of the CDAC array corresponding to the most significant bit of the 10-bit trimming code, and capacitor 818, capacitor 820, capacitor 822, capacitor 824, and capacitor 826 are the portion of the CDAC array corresponding to the least significant bit of the 10-bit trimming code. Specifically, capacitor 810, capacitor 812, capacitor 814, and capacitor 816 represent the trimming bit b. 9:5 , and capacitors 818, 820, 822, 824, and 826 represent the trimming bits b of the 10-bit trimming code 4:0 The bottom plates of capacitor 810, capacitor 812, capacitor 814, capacitor 816, capacitor 818, capacitor 820, capacitor 822, capacitor 824, capacitor 826, and capacitor 828 may depend on their corresponding trimming positions. 9:0 Is it set to a specified logic value (e.g., logic value 1) and switched from ground to the reference voltage V REF As an example, if bit b9 of the 10-bit trim code is set to a logic value of 1, the bottom plate of capacitor 810 is connected to the reference voltage V REF Alternatively, if bit b9 of the 10-bit trim code is set to a logic value of 0, the bottom plate of capacitor 810 is connected to the ground reference.

[0061] During one half cycle (e.g., the positive voltage half cycle), capacitors 810, 812, 814, 816, 818, 820, 822, 824, 826, and 828 of one of the CDAC arrays will be grounded and discharged, while in the other CDAC array, the bottom plates of capacitors 810, 812, 814, 816, 818, 820, 822, 824, 826, and 828 are switched from ground (e.g., 0 volts) to a reference voltage V REF In the next half cycle (e.g., the negative voltage half cycle), the roles of the CDAC array will be reversed by switching the bottom plates of capacitors 810, 812, 814, 816, 818, 820, 822, 824, 826, and 828 from ground (e.g., 0 volts) to a reference voltage V REF , Figure 8 Node A and Node B are pre-charged to V REF Pre-charged to V REF A fraction of , in turn, controls the charging time of the trimmable capacitor component 804 and the trimmable capacitor component 806, the time period of the oscillator, and the frequency of the oscillator. Equation 7, presented below, defines the capacitor charging current Ic based on the 10-bit trimming code.

[0062]

[0063] In Equation 7, T represents the time period of the oscillator; Ic represents the capacitor charging current supplied by the current source component; V REF Represents the reference voltage supplied to the comparator; C fix represents the capacitance value of capacitor 808 in CDAC; C represents the capacitance value of capacitor 818 and capacitor 828; and b m represents the trimming bits of a 10-bit trimming code. Equation 7 can be modified accordingly based on the number of trimming bits.

[0064] Although Figure 8 A CDAC array utilizing a 10-bit trimming code is shown, but other embodiments may use other trimming code lengths depending on the trimming range. As an example, the oscillator may include one or more 8-bit CDAC arrays that provide a lower trimming resolution, rather than using one or more 10-bit segmented CDAC arrays. Within the 8-bit CDAC array, bit b 7:0Can be associated with varying capacitance values. In one embodiment, bit b0 to bit b7 can have capacitance values ​​of C, 2C, 4C, 8C, 16C, 32C, 64C, and 128C, respectively. The oscillator can use an 8-bit CDAC instead of a 10-bit split CDAC array, depending on the process technology of the trimmable capacitor component 804 and the trimmable capacitor component 806 and / or the amount of comparator delay.

[0065] Fig. 9 is a flow chart of an embodiment of a method 900 for trimming multiple components within a precision oscillator to stabilize and achieve a target frequency. Figure 1 and Figure 3 As an example, the method 900 may be implemented for the oscillator 100 and the oscillator 300. The method 900 may also be applied to other types of relaxation oscillators that utilize a current source to charge a capacitor and compare the capacitor voltage to a reference voltage. The method 900 begins at block 902 to trim one or more trimmable resistor components within a current source component to compensate for process variations of the trimmable resistor components. Figure 5 , the method 900 performs trimming to compensate for the varying resistance values ​​due to process variations using the RDAC component 504 and the RDAC component 510. The method 900 can determine whether the resistance values ​​of the RDAC component 504 and the RDAC component 510 are outside of a target range (e.g., within 5%-6% of the target resistance value). If so, the method 900 converts the resistance offset into a resistor trimming bit to adjust the resistance values ​​of the RDAC component 504 and the RDAC component 510 to be closer to the target resistance value.

[0066] Method 900 may then move to block 904 and perform temperature slope trimming within the current source component to compensate for the frequency temperature coefficient of the oscillator. Figure 6 In the method 900, the capacitor charging current Ic affects the frequency of the oscillator. CON and the second current portion I PTAT In other words, the method 900 can increase or decrease the constant current I CON to achieve the target frequency output of the oscillator. Method 900 may then proceed to block 906 and trim the residual amplitude error within one or more capacitor components. Fig. 9 As discussed, method 900 may implement block 906 using a CDAC that trims the charged capacitors. In one or more implementations, method 900 may trim the capacitance according to a 10-bit trim code that switches the bottom plates of capacitors within the CDAC array from ground (e.g., 0 volts) to a reference voltage V REF Other embodiments may utilize other trim code resolutions, such as 9-bit trim codes.

[0067] At least one embodiment is disclosed, and variations, combinations and / or modifications of the features of (multiple) embodiments and / or (multiple) embodiments made by a person of ordinary skill in the art are within the scope of the present disclosure. Alternative embodiments resulting from combining, integrating and / or omitting the features of (multiple) embodiments are also within the scope of the present disclosure. Where a numerical range or limitation is clearly stated, such a clear range or limitation may be understood to include iterative ranges or limitations of similar magnitude that fall within the clearly stated range or limitation (e.g., from about 1 to about 10 includes 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Unless otherwise stated, the use of the term "about" means ±10% of the subsequent number.

[0068] Although several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. This example is to be considered illustrative and not restrictive, and the invention is not limited to the details given herein. For example, various elements or components may be combined or integrated in another system, or certain features may be omitted or not implemented.

[0069] In addition, the techniques, systems, subsystems and methods described and shown as discrete or separate in various embodiments can be combined or integrated with other systems, modules, techniques or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled to each other or directly coupled to each other or communicating with each other can be indirectly coupled or communicated by electrical, mechanical or other means through some interfaces, devices or intermediate components.

Claims

1. An oscillator, comprising: Trimmable capacitors; a trimmable current source coupled to the trimmable capacitor, wherein the trimmable current source comprises: a first trimmable resistor and a second trimmable resistor, and wherein the first trimmable resistor and the second trimmable resistor each comprise: a fixed resistor; a plurality of resistors; and a first plurality of switches, each of the first plurality of switches being coupled to a respective one of the plurality of resistors; and a bias circuit coupled to the trim control, wherein the bias circuit includes a first portion of current coupled to the first trimmable resistor and a second portion of current coupled to the second trimmable resistor; a comparator coupled to the trimmable current source, the comparator including a comparator output; and a data storage element coupled to the comparator output, the data storage element comprising one of a flip-flop and a latch; The bias circuit comprises: A plurality of transistors and a second plurality of switches are coupled in parallel, and wherein each of the second plurality of switches is coupled to a respective drain of the plurality of transistors.

2. An oscillator according to claim 1, wherein: The comparator includes a negative input; and The negative input is coupled to a voltage reference.

3. The oscillator according to claim 1, wherein: The trimmable capacitor comprises: a first capacitor; a first plurality of capacitors coupled in parallel, the first plurality of capacitors coupled to the first capacitor; and A second plurality of capacitors are coupled in parallel, the second plurality of capacitors being coupled to the first capacitor.

4. The oscillator according to claim 1, wherein: The trimmable capacitor is coupled to the first switch and the second switch; The first switch is coupled to ground; and The second switch is coupled to the trimmable current source. 5 . The oscillator of claim 1 , wherein the trimmable current source comprises a trim control coupled to the first trimmable resistor and the second trimmable resistor.

6. The oscillator of claim 1, wherein the trimmable current source comprises a trimming system coupled to the bias circuit and the trimming control.

7. The oscillator of claim 6, wherein the trimming system comprises a current measurement component.

8. An oscillator, comprising: Trimmable capacitors; a trimmable current source coupled to the trimmable capacitor, wherein the trimmable current source comprises: a first trimmable resistor and a second trimmable resistor, and wherein the first trimmable resistor and the second trimmable resistor each include: a fixed resistor; a plurality of resistors; and a plurality of switches, each of the plurality of switches coupled to a respective one of the plurality of resistors; and a bias circuit coupled to the trim control, wherein the bias circuit includes a first portion of current coupled to the first trimmable resistor and a second portion of current coupled to the second trimmable resistor; a comparator coupled to the trimmable current source, the comparator including a comparator output; and a data storage element coupled to the comparator output, the data storage element comprising one of a flip-flop and a latch, wherein the trimmable current source comprises: a first amplifier coupled to a first transistor, the first transistor coupled to the second portion of current and the second trimmable resistor; a second amplifier coupled to a second transistor, the second transistor coupled to the second trimmable resistor; and A third amplifier is coupled to a third transistor, the third transistor being coupled to the first portion of current and the first trimmable resistor.

9. An oscillator according to claim 8, wherein: The comparator includes a negative input; and The negative input is coupled to a voltage reference.

10. The oscillator of claim 8, wherein the trimmable capacitor comprises: a first capacitor; a first plurality of capacitors coupled in parallel, the first plurality of capacitors coupled to the first capacitor; as well as A second plurality of capacitors are coupled in parallel, the second plurality of capacitors being coupled to the first capacitor.

11. The oscillator according to claim 8, wherein: The trimmable capacitor is coupled to the first switch and the second switch; The first switch is coupled to ground; and The second switch is coupled to the trimmable current source.

12. The oscillator of claim 8, wherein the trimmable current source comprises a trimming system coupled to the bias circuit and the trimming control.

13. The oscillator of claim 12, wherein the trimming system comprises a current measurement component.

14. An oscillator comprising a current source, the current source comprising: a bias circuit comprising a first current; a first trimmable resistor and a second trimmable resistor coupled to the bias circuit; a trimming system configured to measure the first current and determine an offset based on the first current; as well as a trim control coupled to the trimming system and to the first trimmable resistor and the second trimmable resistor, the trimming control configured to trim the first trimmable resistor based on the offset; wherein the first trimmable resistor and the second trimmable resistor each include: a fixed resistor; a plurality of resistors; and a first plurality of switches, each of the first plurality of switches being coupled to a corresponding one of the plurality of resistors; wherein the bias circuit is coupled to the trim control, further wherein the bias circuit includes the first current coupled to the first trimmable resistor and the second current coupled to the second trimmable resistor, and wherein the bias circuit further includes: a plurality of transistors coupled in parallel and a second plurality of switches, and wherein each of the second plurality of switches is coupled to a corresponding drain of the plurality of transistors.

15. The oscillator of claim 14, wherein the first current is configured to be adjusted by setting the second plurality of switches to an open or closed state in response to a code.

16. The oscillator of claim 14, wherein the second current is configured to be adjusted by setting the second plurality of switches to an open or closed state in response to a code.

17. The oscillator according to claim 14, further comprising: a first amplifier coupled to a first transistor, the first transistor coupled to the second current and the second trimmable resistor; a second amplifier coupled to a second transistor, the second transistor coupled to the second trimmable resistor; as well as A third amplifier is coupled to a third transistor, the third transistor being coupled to the first current and the first trimmable resistor.

18. The oscillator of claim 14, wherein the trimming system comprises a current measurement component configured to measure the first current at a first test pin in response to the trimming control closing a current mirror switch in the bias circuit.

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