Programmable resistors, bandgap reference sources and adjustment methods

Abstract

This disclosure provides a programmable resistor, a bandgap reference source, and an adjustment method. The programmable resistor includes: a first resistor; a first switch group connected in series with the first resistor to connect the first resistor to two programming ports for programming the resistance value of the first resistor; a second switch group connected in series with the first resistor to connect the first resistor to two sampling ports; and an inverter for controlling the connection or disconnection of the first and second switch groups. The first resistor is a variable resistor, and the first and second switch groups are not connected simultaneously. The programmable resistor of this disclosure has a simple structure and is easy to adjust. When introduced into a bandgap reference source circuit, it can achieve multiple low-cost adjustments after packaging.

Description

Technical Field

[0001] This disclosure relates to the field of analog integrated circuit technology, and in particular to a programmable resistor, a bandgap reference source, and a method for adjusting it. Background Technology

[0002] Analog circuits provide power to circuit systems and convert signals from the analog domain to the digital domain and vice versa, forming the foundation of circuit systems. Bandgap reference sources are crucial basic units in analog circuits. However, due to fluctuations in the process parameters of integrated circuit foundries, the output voltage of bandgap reference sources will have a certain deviation after tape-out, requiring adjustment.

[0003] Currently used laser trimming and resistor network trimming methods have drawbacks such as high cost, low precision, low integration, and difficulty in repeated trimming.

[0004] Meanwhile, in the field of analog integrated circuits, a 256-order digital potentiometer circuit structure is commonly used to adjust the resistance value of a variable resistor. However, to implement a 256-order digital potentiometer, 256 resistors with the same resistance value need to be integrated inside the potentiometer, and a set of 256-to-1 analog switches is also required, resulting in a large circuit area, complex circuitry, and high cost for the digital potentiometer. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the existing technical problems, this disclosure provides a programmable resistor, a bandgap reference source, and an adjustment method, which at least partially solve the above-mentioned technical problems.

[0007] (II) Technical Solution

[0008] This disclosure provides a programmable resistor, comprising: a first resistor; a first switch group connected in series with the first resistor for connecting the first resistor to two programming ports to program the resistance value of the first resistor; a second switch group connected in series with the first resistor for connecting the first resistor to two sampling ports; and an inverter for controlling the connection or disconnection of the first switch group and the second switch group; wherein the first resistor is a variable resistor, and the first switch group and the second switch group are not connected simultaneously.

[0009] Optionally, the variable resistor is non-volatile.

[0010] Optionally, the variable resistor can be a memristor, and the materials of the memristor include ferroelectric materials, phase change materials, and magnetic materials.

[0011] Optionally, the second switch group includes a first switch and a second switch, the first switch and the second switch being connected in series with a first resistor respectively; the programmable resistor further includes: a second resistor, connected in series with a sampling port, and connected in series with either the first switch or the second switch.

[0012] Another aspect of this disclosure provides a bandgap reference source, including: a programmable resistor as described in any embodiment of this disclosure; and a first transistor and a second transistor; wherein the emitter area of ​​the second transistor is an integer multiple of the emitter area of ​​the first transistor; the programmable resistor is connected in series with the base of the first transistor and in series with the base of the second transistor, respectively, for adjusting the output voltage of the bandgap reference source.

[0013] Optionally, both the first transistor and the second transistor are NPN transistors; the bandgap reference source further includes a temperature resistor and a bias resistor; wherein the emitter of the second transistor is connected to the temperature resistor, the temperature resistor is connected to the first end of the bias resistor, and the emitter of the first transistor is connected to the first end of the bias resistor.

[0014] Optionally, the bandgap reference source is used to provide a reference voltage signal for any one of the operational amplifier circuit, analog reference source circuit, analog-to-digital converter circuit, digital-to-analog converter circuit, and linear regulator circuit.

[0015] This disclosure also provides a method for adjusting a bandgap reference source as described in any embodiment of this disclosure, comprising: applying a selection signal to an inverter to control the connection of a first switch group and the disconnection of a second switch group; applying programming voltage signals to a third switch and a fourth switch in the first switch group through two programming ports to adjust the resistance value of a first resistor; applying a selection signal to an inverter to control the connection of the second switch group and the disconnection of the first switch group; sampling the first switch and the second switch through two sampling ports to determine the resistance value of the first resistor; and repeatedly adjusting and determining the resistance value of the first resistor to reduce the output voltage deviation of the bandgap reference source.

[0016] (III) Beneficial Effects

[0017] Compared with the prior art, the programmable resistor, bandgap reference source, and adjustment method provided in this disclosure have at least the following advantages:

[0018] (1) The programmable resistor disclosed herein requires only one resistive switching device, at most one resistor, four analog switches, and one inverter. The number of devices is greatly reduced, the circuit area of ​​the variable resistor is greatly reduced, and the cost is reduced.

[0019] (2) The bandgap reference source of this disclosure introduces a programmable resistor to offset the reference source voltage output deviation caused by the current amplification factor of the transistor and the fluctuation of the forward emission factor, thereby realizing the fine adjustment of the output voltage of the bandgap reference source. The programmable resistor occupies a very small circuit area, and the circuit is simple and low in cost. Attached Figure Description

[0020] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0021] Figure 1 A circuit diagram of a programmable resistor according to an embodiment of the present disclosure is shown schematically;

[0022] Figure 2 A circuit diagram of another programmable resistor according to an embodiment of the present disclosure is shown schematically;

[0023] Figure 3 A circuit diagram of a bandgap reference source according to an embodiment of the present disclosure is shown schematically;

[0024] Figure 4 The illustration schematically shows a method for adjusting a bandgap reference source according to an embodiment of the present disclosure. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0026] It should be noted that similar or identical parts are referred to by the same reference numerals in the accompanying drawings or description. The technical features of the various embodiments exemplified in the specification can be freely combined to form new solutions without conflict. Furthermore, each claim can stand alone as an embodiment, or the technical features in the various claims can be combined to form new embodiments. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated in a simplified or convenient manner. Moreover, elements or implementations not shown or described in the drawings are those known to those skilled in the art. Additionally, although this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints.

[0027] Unless there are technical obstacles or contradictions, the various embodiments described above in this disclosure can be freely combined to form other embodiments, all of which are within the protection scope of this disclosure.

[0028] Although this disclosure has been described in conjunction with the accompanying drawings, the embodiments disclosed in the drawings are intended to illustrate preferred embodiments of this disclosure and should not be construed as limiting the disclosure. The dimensions in the drawings are merely illustrative and should not be construed as limiting the disclosure.

[0029] While some embodiments of the general concept of this disclosure have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the general concept of this disclosure, the scope of which is defined by the claims and their equivalents.

[0030] Figure 1 A circuit diagram of a programmable resistor according to an embodiment of the present disclosure is shown schematically.

[0031] According to embodiments of this disclosure, such as Figure 1 As shown, a programmable resistor includes, for example: a first resistor A; a first switch group, connected in series with the first resistor A, for connecting the first resistor A to two programming ports Vp+ and Vp-, to program the resistance value of the first resistor A; a second switch group, connected in series with the first resistor A, for connecting the first resistor A to two sampling ports R+ and R-; and an inverter INV, for controlling the connection or disconnection of the first and second switch groups. The first resistor A is a variable resistor, and the first and second switch groups are not connected simultaneously. By controlling the connection or disconnection of the first and second switch groups through the inverter INV, the resistance value of the first resistor A can be programmed and adjusted, and the resistance value of the first resistor A can be determined when the programmable resistor is applied to other circuits such as a bandgap reference source.

[0032] According to embodiments of this disclosure, the variable resistor is non-volatile. The non-volatile nature of the variable resistor allows for one-time adjustment of its resistance value, and also supports fine-tuning after packaging. Compared to traditional 256-step digital potentiometers, the circuit area is significantly reduced, decreasing wafer costs during manufacturing. Simultaneously, the problem of resistance value consistency caused by multiple resistors is eliminated, and laser fine-tuning during manufacturing is unnecessary, further reducing production costs.

[0033] For example, a variable resistor is a memristor, and memristors are made of materials including ferroelectric materials, phase change materials, and magnetic materials. The resistance value of a memristor can be continuously adjusted without fixed order limitations. Theoretically, continuous resistance values ​​can be obtained within a certain range, greatly expanding the application range of programmable resistors.

[0034] For example, the second switch group includes a first switch S3 and a second switch S4, which are connected in series with a first resistor A. The first switch group includes a third switch S1 and a fourth switch S2, which are also connected in series with the first resistor A. The first terminal of the inverter INV is connected to the third switch S1 and the fourth switch S2 to control the connection or disconnection of the third switch S1 and the fourth switch S2. The second terminal of the inverter INV is connected to the first switch S3 and the second switch S4 to control the connection or disconnection of the first switch S3 and the second switch S4.

[0035] For example, the first resistor A has two operating states: a working state and a programming state, which can be selected via the Sel port. When the input signal of the Sel port activates the first switch S3 and the second switch S4, the signal from the inverter INV through the Sel port disconnects the third switch S1 and the fourth switch S2, and the programmable resistor is in the working state. When the signal from the inverter INV through the Sel port activates the third switch S1 and the fourth switch S2, the signal from the inverter INV through the Sel port disconnects the first switch S3 and the second switch S4. The resistance value of the first resistor A can be modified by applying a programming voltage across the Vp+ and Vp- terminals, and the programmable resistor is in the programming state.

[0036] Figure 2 A circuit diagram of another programmable resistor according to an embodiment of the present disclosure is shown schematically.

[0037] According to embodiments of this disclosure, in order to improve the stability of programmable resistors, such as Figure 2 As shown, the programmable resistor may further include, for example, a second resistor B, which is connected in series with a sampling port R+ and with a first switch S3. Alternatively, it may be connected in series with another sampling port R- and with a second switch S4.

[0038] For example, the second resistor B can be a thin film resistor, a complementary metal oxide semiconductor (CMOS) resistor, etc., with a fixed resistance value. It can be set according to the requirements of the application during manufacturing, such as 0Ω, 1KΩ, etc.

[0039] Figure 3 A circuit diagram of a bandgap reference source according to an embodiment of the present disclosure is shown schematically.

[0040] According to embodiments of this disclosure, such as Figure 3 As shown, the bandgap reference source includes, for example, a programmable resistor R as described in any embodiment of this disclosure. calAnd a first transistor Q1 and a second transistor Q2. The emitter area of ​​the second transistor Q2 is an integer multiple of the emitter area of ​​the first transistor Q1. Programmable resistor R cal These transistors are connected in series with the bases of the first transistor Q1 and the second transistor Q2, respectively, to adjust the output voltage of the bandgap reference source. A programmable resistor R is introduced. cal This allows the bandgap reference source to be adjusted after packaging, eliminating the need for a factory environment and further reducing costs. Simultaneously, it eliminates the need to adjust the programmable resistor R. cal Its physical form supports large-scale, high-density integration. Programmable resistor R cal It supports multiple adjustments, allowing the bandgap reference source performance to be readjusted according to the usage environment to obtain the optimal performance under the current environment.

[0041] For example, both the first and second transistors are NPN transistors. The bandgap reference source also includes a temperature resistor R. t and bias resistor R be Among them, the emitter of the second transistor Q2 is connected to the temperature resistance R. t Connected, temperature resistance R t With bias resistor R be The first terminal is connected to the first transistor Q1, and the emitter of the first transistor Q1 is connected to the bias resistor R. be The first end is connected.

[0042] For example, current is supplied to the first transistor Q1 and the second transistor Q2 through a first current source Is1 and a second current source Is2, respectively. The bases of the first transistor Q1 and the second transistor Q2 are directly connected without a programmable resistor R. cal Assume the emitter area ratio of the first transistor Q1 and the second transistor Q2 is 1:m. Based on Gilbert loop analysis, the flow rate through the temperature resistance R... t Current:

[0043]

[0044] Among them, V t Temperature resistance R t The voltage across the two ends. Therefore, the voltage output of the bandgap reference source:

[0045]

[0046] Among them, VB E1 For bias resistor R be The voltage across the terminals. However, transistors fabricated using actual CMOS technology exhibit non-ideal characteristics, primarily including a finite current amplification factor β and a non-ideal forward emitter factor n. f≠1. Therefore, the actual output voltage of the bandgap reference source can be expressed as:

[0047]

[0048] Among them, the non-ideal factors β and n f Fluctuations in manufacturing processes can cause variations in the reference source voltage output across different chips. Deviation analysis of these factors yields the following results:

[0049]

[0050] in,

[0051]

[0052]

[0053] Taking SMIC's (Semiconductor Manufacturing International Corporation) 180nm process as an example: A bandgap reference source is implemented using SMIC's 180nm CMOS process. The design parameters of the reference source are as follows: unit resistance R... u = 2.083KΩ, temperature resistance R t =2R u Bias resistor R be =9.75R u The ratio of the number of transistors is m = 8. The transistor process parameters are as follows: current amplification factor β = 19.847, process variation dβ = 2.977. Forward emitter factor n f =1.006, process fluctuation dn f =0.00503. Substituting into the above deviation analysis formula (4), the deviation of the reference source voltage output caused by process fluctuations can be obtained: dV bgr =13.2mV.

[0054] A programmable resistor R is added between the bases of the first transistor Q1 and the second transistor Q2. cal At that time, we can obtain:

[0055]

[0056] Similarly, by performing a deviation analysis, we obtain:

[0057]

[0058] The newly introduced term can be used to offset the fluctuations of the aforementioned two factors:

[0059]

[0060] Design value R of resistive switching device cal= 5.4KΩ, from which we can deduce that in order to compensate for the process parameters β and n f The deviation caused by fluctuations, and the adjustment range of the memristor resistance value: dR cal = 2.59KΩ, which is consistent with the dR obtained from the actual circuit simulation. cal =1.5KΩ, the result is similar.

[0061] It should be noted that the deviation analysis is not a linear superposition, but a statistical analysis.

[0062] For example, a bandgap reference source can be used to provide a reference voltage signal for any of the following: operational amplifier circuits, analog reference source circuits, analog-to-digital converter circuits, digital-to-analog converter circuits, and linear voltage regulator circuits.

[0063] Figure 4 The illustration schematically shows a method for adjusting a bandgap reference source according to an embodiment of the present disclosure.

[0064] According to embodiments of this disclosure, such as Figure 4 As shown, the adjustment method for the bandgap reference source includes, for example:

[0065] S410 applies a selection signal to the inverter to control the connection of the first switch group and to control the disconnection of the second switch group.

[0066] For example, the programmable resistor can be switched to programming mode via an external control signal Sel to control its resistance value. Vp+ is the positive terminal of the programming signal, and Vp- is the negative terminal. Applying a specific programming signal to the programmable resistor at these ports allows adjustment of its resistance value. R+ and R- are the signal ports of the programmable resistor, used to connect external sampling signals when applied as a resistor.

[0067] S420 applies programming voltage signals to the third and fourth switches in the first switch group through two programming ports to adjust the resistance value of the first resistor.

[0068] For example, when the Sel signal is set to a specific level, the third switch S1 and the fourth switch S2 are selected. The inverter INV ensures that the first switch S3 and the second switch S4 are in the off state. At this time, the programmable resistor enters the programming state. The first resistor A can be programmed by applying a programming voltage to the Vp+ and Vp- ports.

[0069] S430 applies a selection signal to the inverter to control the connection of the second switch group and to control the disconnection of the first switch group.

[0070] S440 samples the first switch and the second switch through two sampling ports to determine the resistance value of the first resistor.

[0071] For example, when the Sel signal is set to a specific level, the first switch S3 and the second switch S4 are selected. The inverter INV ensures that the third switch S1 and the fourth switch S2 are in the open state. The programmable resistor enters the working state and can sample the resistance value of the first resistor A through the R+ and R- ports and use it as a resistor.

[0072] S450, repeatedly adjust and determine the resistance value of the first resistor to reduce the output voltage deviation of the bandgap reference source.

[0073] In summary, this disclosure presents a programmable resistor and a bandgap reference source. By controlling the first and second switching groups with an inverter, the programmable resistor is switched between its programmed and operational states. This reduces the number of components, significantly decreasing the circuit area of ​​the variable resistor and lowering costs. Furthermore, by introducing a programmable resistor into the bandgap reference source, it can be easily and cost-effectively adjusted multiple times after packaging, greatly improving its applicability.

[0074] Details not covered in the method embodiment section are similar to those in the device embodiment section; please refer to the device embodiment section for further details, which will not be repeated here.

[0075] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to a specific order or hierarchy.

[0076] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted when they may cause confusion in understanding this disclosure. Furthermore, the shapes, sizes, and positional relationships of the components in the drawings do not reflect their actual size, scale, or actual positional relationships.

[0077] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, this disclosure is in a state of having fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of this disclosure.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified. The term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as "including" is used as a conjunction in the claims. The use of any term "or" in the specification or claims is intended to mean "non-exclusive or."

[0079] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A bandgap reference source, characterized by, include: Programmable resistors, first transistor, second transistor, temperature resistor, and bias resistor; The programmable resistor includes: a first resistor; a first switch group connected in series with the first resistor to connect the first resistor to two programming ports for programming the resistance value of the first resistor; a second switch group connected in series with the first resistor to connect the first resistor to two sampling ports; and an inverter for controlling the connection or disconnection of the first switch group and the second switch group; wherein the first resistor is a variable resistor, and the first switch group and the second switch group are not connected simultaneously. The emitter area of ​​the second transistor is an integer multiple of the emitter area of ​​the first transistor; both the first transistor and the second transistor are NPN transistors. The programmable resistor is connected in series with the base of the first transistor and the base of the second transistor, respectively, to adjust the output voltage of the bandgap reference source; The emitter of the second transistor is connected to the temperature resistor, the temperature resistor is connected to the first end of the bias resistor, and the emitter of the first transistor is connected to the first end of the bias resistor.

2. The bandgap reference source of claim 1, wherein, The variable resistor is non-volatile.

3. The bandgap reference source according to claim 2, characterized in that, The variable resistor is a memristor, and the materials of the memristor include ferroelectric materials, phase change materials, and magnetic materials.

4. The bandgap reference source according to claim 1, characterized in that, The second switch group includes a first switch and a second switch, wherein the first switch and the second switch are respectively connected in series with the first resistor; The programmable resistor further includes: The second resistor is connected in series with one of the sampling ports and in series with either the first or the second switch.

5. The bandgap reference source according to claim 1, characterized in that, The bandgap reference source is used to provide a reference voltage signal for any one of the operational amplifier circuit, analog reference source circuit, analog-to-digital converter circuit, digital-to-analog converter circuit, and linear voltage regulator circuit.

6. A method for adjusting a bandgap reference source as described in any one of claims 1 to 5, characterized in that, include: A selection signal is applied to the inverter to control the connection of the first switch group and to control the disconnection of the second switch group; Programming voltage signals are applied to the third and fourth switches in the first switch group through two programming ports to adjust the resistance value of the first resistor. A selection signal is applied to the inverter to control the connection of the second switch group and to control the disconnection of the first switch group; The resistance value of the first resistor is determined by sampling the first switch and the second switch through two sampling ports respectively. as well as The resistance value of the first resistor is repeatedly adjusted and determined to reduce the output voltage deviation of the bandgap reference source.

Images