High precision integral nonlinearity assessment

Abstract

Embodiments of the present disclosure may comprise a system to determine integral nonlinearity of a device-under-test, the system comprising a measurement setup, with a voltage source to set a top voltage. Further the system comprises a multiplexer to selectively couple the set top voltage to the device-under-test or to selectively couple a bottom voltage to the device-under test. A processor is operable to record a plurality of measurements of the set top voltage and the bottom voltage and compute integral nonlinearity.

Description

HIGH PRECISION INTEGRAL NONLINEARITY ASSESSMENTTECHNICAL FIELD

[0001] The present disclosure generally relates to a method and system for high precision integral nonlinearity assessment.BACKGROUND

[0002] Aspects of the present disclosure relate to a method and system for high precision integral nonlinearity assessment. In this regard, conventional integral nonlinearity assessment may be costly, cumbersome, and / or inefficient.

[0003] Limitations and disadvantages of conventional systems and methods will become apparent to one of skill in the art, through comparison of such approaches with some aspects of the present methods and systems set forth in the remainder of this disclosure with reference to the drawings.BRIEF SUMMARY OF THE DISCLOSURE

[0004] Shown in and / or described in connection with at least one of the figures, and set forth more completely in the claims is a method and system for high precision integral nonlinearity assessment.

[0005] These and other advantages, aspects and novel features of the present disclosure, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The various features and advantages of the present disclosure may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements.

[0007] FIG. 1A is a flowchart illustrating a method, according to some embodiments of the present disclosure.

[0008] Figure 1 B is a flowchart extending from figure 1A and further illustrating the method, according to some embodiments of the present disclosure.

[0009] FIG. 2 is a block diagram illustrating a system, according to some embodiments of the present disclosure.

[0010] FIG. 3 is an exemplary circuit diagram according to some embodiments of the present disclosure.

[0011] FIG. 4 is a graph illustrating an exemplary recording of top voltages and bottom voltages, according to some embodiments of the disclosure.

[0012] FIG. 5 is a graph illustrating an exemplary linear fit to a set of measurement ratios, according to some embodiments of the disclosure.DETAILED DESCRIPTION

[0013] The following discussion provides various examples of a method and system for high precision integral nonlinearity assessment. Such examples are non-limiting, and the scope of the appended claims should not be limited to the particular examples disclosed. In the following discussion, the terms “example” and “e.g.,” are non-limiting.

[0014] The figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. In addition, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the examples discussed in the present disclosure. The same reference numerals in different figures denote the same elements.

[0015] The term “or” means any one or more of the items in the list joined by “or”. As an example, “x or y” means any element of the three-element set {(x), (y), (x, y)}. As another example, “x, y, or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}.

[0016] The terms “comprises,” “comprising,” “comprises,” and / or “comprising,” are “open ended” terms and specify the presence of stated features, but do not preclude the presence or addition of one or more other features.

[0017] The terms “first,” “second,” etc. may be used herein to describe various elements, and these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, for example, a first element discussed in this disclosure could be termed a second element without departing from the teachings of the present disclosure.

[0018] Unless specified otherwise, the term “coupled” may be used to describe two elements directly contacting each other or describe two elements indirectly connected by one or more other elements. For example, if element A is coupled to element B, then element A can be directly contacting element B or indirectly connected to element B by an intervening element C. Similarly, the terms “over” or “on” may be used to describe two elements directlycontacting each other or describe two elements indirectly connected by one or more other elements.

[0019] Embodiments of the present disclosure may comprise a method to determine integral nonlinearity of a device-under-test (DUT), the method comprising setting a top voltage, for each of a plurality of top voltages balancing a measurement setup. Embodiments may also comprise selectively coupling a set top voltage to the DUT.

[0020] Embodiments may also comprise recording a plurality of measurements of the set top voltage by the DUT over a first measurement time period. Embodiments may also comprise determining an amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage. Embodiments may also comprise selectively coupling a bottom voltage to the DUT.

[0021] Embodiments may also comprise recording a plurality of measurements of the bottom voltage by the DUT over a second measurement time period. Embodiments may also comprise determining an amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. Embodiments may also comprise determining a measured ratio based on the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage and the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. Embodiments may also comprise determining a best fit of a model equation to the set of measured ratios. In some embodiments, each of the measured ratios may be associated with a corresponding one of the plurality of top voltages.

[0022] In some embodiments, the method may comprise determining integral nonlinearity of a DUT based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at the DUT. In some embodiments, the measurement setup may be an impedance bridge or a Wheatstone bridge. In some embodiments, the measurement setup may comprise a plurality of voltage sources.

[0023] In some embodiments, the measurement setup may comprise two impedance standards. In some embodiments, the two impedance standards may be voltage-stable. In some embodiments, the two impedance standards may be characterized by an impedance ratio of 1 / n. In some embodiments, the method may comprise using a multiplexer to selectively couple the top voltage or the bottom voltage to the DUT.

[0024] In some embodiments, the DUT may be an analog-to-digital converter. In some embodiments, the set top voltage may be a sinusoidal voltage signal. Embodiments may also comprise a first measurement time period that may be substantially equal to a secondmeasurement time period. In some embodiments, the method may comprise determining fundamental frequency components using a discrete Fourier transform.

[0025] In some embodiments, the model equation may be defined as- r4]) . In some embodiments, the method may comprise determining the best fit of the model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach, a root mean squared error approach, a minimum variance approach, an R-squared approach, or any other suitable model fitting approach.

[0026] In some embodiments, the method may comprise balancing the measurement setup by adjusting an auxiliary voltage to zero a difference voltage. In some embodiments, the method may comprise selecting each of the plurality of top voltages between 10% to 100% of the input voltage range of the DUT.

[0027] Embodiments of the present disclosure may also comprise a system to determine integral nonlinearity of a device-under-test (DUT), the system comprising a measurement setup, comprising a voltage source to set a top voltage. Embodiments may also comprise a multiplexer to selectively couple a set top voltage to the DUT or to selectively couple a bottom voltage to the DUT.

[0028] Embodiments may also comprise a processor operable to record a plurality of measurements of the set top voltage by the DUT over a first measurement time period. In some embodiments, the processor may be operable to determine an amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage. In some embodiments, the processor may be further operable to record a plurality of measurements of the bottom voltage by the DUT over a second measurement time period.

[0029] In some embodiments, the processor may be further operable to determine an amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. In some embodiments, the processor may be further operable to determine a measured ratio based on the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage and the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage.

[0030] In some embodiments, the processor may be further operable to determine a best fit of a model equation to the set of measured ratios. In some embodiments, each of the measured ratios may be associated with a corresponding one of the plurality of top voltages.

[0031] In some embodiments, the system may be configured to determine integral nonlinearity of a DUT based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at the DUT at the processor. In some embodiments, the measurement setup may be an impedance bridge or a Wheatstone bridge. In some embodiments, the measurement setup may comprise an auxiliary voltage source, operable to balance the measurement setup.

[0032] In some embodiments, the measurement setup may comprise two impedance standards. In some embodiments, the two impedance standards may be voltage-stable. In some embodiments, the two impedance standards may be characterized by an impedance ratio of 1 / n. In some embodiments, the DUT may be an analog-to-digital converter.

[0033] In some embodiments, the set top voltage may be a sinusoidal voltage signal. Embodiments may also comprise a first measurement time period that may be substantially equal to a second measurement time period. In some embodiments, the processor may be operable to determine fundamental frequency components using a discrete Fourier transform. In some embodiments, the model equation may be defined as rm® r 1 - [l - r2] -

[0034] In some embodiments, the processor may be operable to determine the best fit of the model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach, a root mean squared error approach, a minimum variance approach, an R-squared approach, or any other model fitting approach.

[0035] In some embodiments, the system may comprise a difference voltage measurement device operable to balance the measurement setup by adjusting an auxiliary voltage to zero a difference voltage measured by the difference voltage measurement device. Embodiments may also comprise a voltage source wherein each of the plurality of top voltages may be selected to lie in the range between 10% to 100% of the input voltage range of the DUT.

[0036] Testing modern devices, for example analog-to-digital converters, is highly challenging. It is not uncommon now to find analog-to-digital converters with 24-bit resolution, for example. The very high resolution of such devices often makes it impossible to measure non-linearities and errors directly because there are very few measurement devices and voltage sources for testing that are sufficiently precise. Or, such precise measurement devices may be technically feasible but prohibitively expensive. It is thus desirable to provide analternative method and system for high precision integral nonlinearity assessment of devices under test.

[0037] Referring now to FIG. 1 A and FIG. 1 B, FIGS. 1 A to 1 B are flowcharts that describe a method, according to some embodiments of the present disclosure. At 102, the method may comprise setting a top voltage, for each of a plurality of top voltages.

[0038] In some embodiments, at 104, the method may include balancing a measurement setup. At 106, the method may include selectively coupling a set top voltage to the DUT. At 108, the method may include recording a plurality of measurements of the set top voltage by the DUT over a first measurement time period. At 110, the method may include determining an amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage. At 112, the method may include selectively coupling a bottom voltage to the DUT. At 114, the method may include recording a plurality of measurements of the bottom voltage by the DUT over a second measurement time period. At 116, the method may include determining an amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. Each of the measured ratios may be associated with a corresponding one of the plurality of top voltages.

[0039] At 118, the method may include determining a measured ratio based on the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage and the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. At 122, if the method has progressed through the desired set of top voltages to be set at step 102, the method may continue to step 120. Alternatively, if the method has not yet progressed through the desired set of top voltages to be set at step 102, the method may loop back to step 102.

[0040] At 120, the method may include determining a best fit of a model equation to the set of measured ratios.

[0041] In some embodiments, the method may include determining integral nonlinearity of a DUT based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at the DUT. In some embodiments, the measurement setup may be an impedance bridge or a Wheatstone bridge. In some embodiments, the measurement setup may comprise a plurality of voltage sources.

[0042] In some embodiments, the measurement setup may comprise two impedance standards. In some embodiments, the two impedance standards may be voltage-stable. In some embodiments, the two impedance standards may be characterized by an impedance ratio of 1 / n. In some embodiments, the method may include using a multiplexer to selectivelycouple the set top voltage or the bottom voltage to the DUT. In some embodiments, the DUT may be an analog-to-digital converter.

[0043] In some embodiments, the set top voltage may be a sinusoidal voltage signal. In some embodiments, a first measurement time period may be substantially equal to a second measurement time period. In some embodiments, the method may include determining fundamental frequency components using a discrete Fourier transform. In some embodiments, the model equation may be defined as rm~ r 1 - - r4] . In someembodiments, the method may include determining the best fit of the model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach, a root mean squared error approach, a minimum variance approach, an R-squared approach, or any other model fitting approach. In some embodiments, the method may include balancing the measurement setup by adjusting an auxiliary voltage to zero a difference voltage. In some embodiments, the method may include selecting each of the plurality of top voltages between 10% to 100% of the input voltage range of the DUT.

[0044] FIG. 2 is a block diagram that describes a system 200, according to some embodiments of the present disclosure. In some embodiments, the system 200 may include a measurement setup 210 and a processor 220 operable to record a plurality of measurements of the set top voltage by the DUT 260 over a first measurement time period. The measurement setup 210 may include a voltage source 212 to set a top voltage and a multiplexer 214 to selectively couple a set top voltage to the DUT 260 or to selectively couple a bottom voltage to the DUT 260.

[0045] In some embodiments, the processor 220 may be operable to determine an amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage. The processor 220 may be further operable to record a plurality of measurements of the bottom voltage by the DUT 260 over a second measurement time period. The processor 220 may be further operable to determine an amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage.

[0046] In some embodiments, the processor 220 may be further operable to determine a measured ratio based on the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage and the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. The processor 220 may be further operable to determine a best fit of a model equationto the set of measured ratios. Each of the measured ratios may be associated with a corresponding one of the plurality of top voltages.

[0047] In some embodiments, the system 200 may be configured to determine integral nonlinearity of a DUT 260 based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at the DUT 260 at the processor. In some embodiments, the measurement setup 210 may be an impedance bridge or a Wheatstone bridge. In some embodiments, the measurement may comprise an auxiliary voltage source operable to balance said measurement setup.

[0048] In some embodiments, the measurement setup 210 may include two impedance standards. In some embodiments, the two impedance standards may be voltage-stable. In some embodiments, the two impedance standards may be characterized by an impedance ratio of 1 / n. In some embodiments, the DUT 260 may be an analog-to-digital converter. In some embodiments, the set top voltage may be a sinusoidal voltage signal. In some embodiments, a first measurement time period may be substantially equal to a second measurement time period.

[0049] In some embodiments, the processor may be operable to determine fundamental frequency components using a discrete Fourier transform. In some embodiments, the model equation may be defined as rm® r 1 - - r4] . In someembodiments, the processor may be operable to determine the best fit of the model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach, a root mean squared error approach, a minimum variance approach, an R-squared approach, or any other model fitting approach.

[0050] In some embodiments, the system 200 may include a difference voltage measurement device operable to balance the measurement setup 210 by adjusting an adjusting an auxiliary voltage to zero a difference voltage measured by the difference voltage measurement device. In some embodiments, at the voltage source each of the plurality of top voltages may be selected between 10% to 100% of the input voltage range of the DUT 260.

[0051] FIG. 3 is a circuit diagram for an exemplary embodiment of the present disclosure. There is shown a system 200 comprising a measurement setup 210, a DUT 260, and a processor 220. The system 200 may be operable to determine the integral nonlinearity of the DUT 260. The system 200 may include a measurement setup 210 and a processor 220 operable to record a plurality of measurements of the set top voltage by the DUT 260 over a first measurement time period.

[0052] The measurement setup 210 may include a voltage source 212 to set a top voltage and a multiplexer 214 to selectively couple a set top voltage to the DUT 260 or to selectively couple a bottom voltage to the DUT 260. The measurements setup 210 may be operable to provide highly accurate top voltages and bottom voltages to the DUT 260 for determining integral non-linearity. A set top voltage may be measured at measurement location 305. A bottom voltage may be measured at measurement location 310. A measurement setup 210 may comprise a voltage source 212, an auxiliary voltage source 225, a first transformer 230, a second transformer 235, a difference voltage measurement device 250, a first impedance standard 240, a second impedance standard 245 and a multiplexer 214.

[0053] The top voltage source 212 may be operable to set a top voltage at measurement location 305. In some embodiments, the set top voltage may be a sinusoidal voltage signal. The voltage source 212 may also provide another voltage signal, such as a ramp, a sawtooth or any other voltage, including a DC voltage. In some embodiments, at the voltage source 212 one or more of the top voltages may be selected between 10% to 100% of the input voltage range of the DUT 260. The set top voltage provided by voltage source 212 may feed a primary winding of a first transformer 230. The first transformer 230 is illustrated with a core next to the primary winding. A secondary winding of a first transformer 230 may split this voltage into a 1 / n ratio, for example, by a ground connection that may be illustrated coupled to the secondary winding of the first transformer 230. An associated bottom voltage may be present at measurement location 310. The first transformer 230 and the second transformer 235 may form the source arms of a Wheatstone bridge / impedance bridge. In accordance with various embodiments of the invention, any winding of the first transformer 230 or the second transformer 235 may use a core or not. Likewise, the function of the first transformer 230 is to provide a voltage ratio on the secondary winding and thus the source arm of the impedance bridge, and the second transformer 235 may be used to fine-tune the voltage ratio. Any other suitable apparatus to perform a similar function may be used instead of the first transformer 230, the second transformer 235, and / or the voltage sources 212, 225.

[0054] The impedance bridge further comprises a first impedance standard 240 and a second impedance standard 245. The first impedance standard 240 and the second impedance standard 245 may comprise any combination of resistance and reactance devices, including but not limited to e.g., resistors, capacitors, and inductors. In some embodiments, the two impedance standards 240, 245 may be voltage-stable, i.e., their impedance is stable over a large range of applied voltages. In some embodiments, the two impedance standards 240, 245 may be characterized by an impedance ratio of 1 / n. The impedance standards 240, 245 may often be highly accurate impedances.

[0055] The auxiliary voltage source 225 may feed the second transformer 235. The second transformer 235 may be an injection detection transformer, for example. By applying a sinusoidal voltage at the auxiliary voltage source 225, for example of the same frequency used at voltage source 212, the auxiliary voltage source 225 may be used to adjust the phase and amplitude of the voltage in the circuit due to the first voltage source 212.

[0056] To balance the measurements setup 210 by balancing the impedance bridge, the auxiliary voltage source 225 may be adjusted such that difference voltage measurement device 250 may indicate a zero voltage at measurement location 315.

[0057] When the measurement setup 210 comprising the impedance bridge is balanced, the impedance ratio of the second impedance standard 245 over the first impedance standard 240 may be given directly by the negative of the ratio of the bottom voltage at measurement location 310 over the set top voltage at measurement location 305.

[0058] where Zbmay be the value of the second impedance standard 245, Ztmay be the value of the first impedance standard 240, Vbmay be the bottom voltage at location 310, and Vtmay be the set top voltage at location 305.

[0059] The multiplexer 214 may be operable to switch its input between two sources and feed either of them to its output. For example, the multiplexer 214 illustrated in FIG. 3 may switch between two inputs and feed either to its output at measurement location 320. That is, the multiplexer 214 provides either Vt, Vbto the input of the DUT 260, i.e., Vt= {Vt,Vb) at measurement location 320. Correspondingly, at the output of the DUT 260, we may observer either an output V0lltdue to an input Vt. or Vb. For simplicity, we may refer to the output voltage of the DUT 260 as a function of Vtas V0llt= f(Vt) = Vto. Similarly, if the output voltage of the DUT 260 may depend on Vb, we may refer to Vout= f(Vb) = Vb0.

[0060] Thus, the DUT 260 may be fed either a Vbor a Vtto its input repeatedly, so that for many values of {Vto} and associated {V&o}, the DUT 260 outputs may be analysed by discrete Fourier transform in the processor 220.

[0061] From the discrete Fourier transform obtained, we may desire to obtain the amplitude of the fundamental frequency component (amplitude 1. 1 at frequency fo). We may denote it as follows, depending on whether the output of the DUT 260 depends on Vtor Vb|7't0| = |DFT{7to} / = / o||&0| = |DFT{7&0} / = / o|

[0062] where we have used the notation to indicate the amplitude of the fundamental frequency component |7't0| #= |7t0| , because the DUT 260 may introduce distortion and therefore harmonic frequency components into its output signal. Correspondingly, the amplitude of the fundamental frequency component at fo may be different from the amplitude of the output signal as a whole.

[0063] Further, a measured ratio rmmay be defined by:

[0064] rmmay be approximated by a model equation for sinusoidal voltage sources 212, 225 at a same frequency:where |7t| may denote the amplitude of the input signal Vt, i.e., Vt= |7t|sin (2nfot). And 7^7 = = = r. The impedance bridge is assumed balanced.

[0065] The parameters b and d may be determined by fitting a set of measured ratios {rm} to the model equation shown in Eq. 1 . This will be illustrated in FIG. 5 below.

[0066] FIG. 4 is a graph illustrating an exemplary recording of top voltages and bottom voltages, according to some embodiments of the disclosure. Referring to FIG. 4, on the graph, the horizontal axis 402 may indicate time, the vertical axis 404 may indicate amplitude. The impedance bridge is assumed to be balanced. In the first half of the graph, the multiplexer 214 may be set to feed a set top voltage Vtto the DUT 260, as shown by the solid black line 406. During this time, i.e., the first measurement time period, outputs of the DUT 260 may be recorded at the processor 220, indicated by the grey solid circles. These outputs may be similar but generally not identical to the input signal, due to imperfections and non-linearities of the DUT 260.

[0067] After some time, the multiplexer 214 may switch to feed the bottom voltage Vbto the DUT 260, as indicated by the solid black line 408. The switch can be seen in the horizontal center of the graph. During the transition, the processor 220 would generally not record output data from the DUT 260, due to the transition characteristics of the signal. During this time, i.e., the second half of the graph (the second measurement time period), outputs of the DUT 260 may be recorded at the processor 220, indicated by the black solid squares. These outputs may be similar but generally not identical to the input signal, due to imperfections and nonlinearities of the DUT 260.

[0068] In some embodiments, the DUT 260 may be an analog-to-digital converter. In some embodiments, a first measurement time period may be substantially equal to a second measurement time period.

[0069] From these recorded output voltages, the processor 220 may determine the amplitude of the fundamental frequency components, as described above, for example by using a discrete Fourier transform. Other approaches may be envisaged to determine the fundamental frequency component, such as precision filtering, locked-in amplifiers etc., as known to someone skilled in the art.

[0070] Thus, the processor 220 may be operable to determine an amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage. Similarly, the processor 220 may be further operable to determine an amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage.

[0071] With the determined amplitudes of the fundamental frequency components for both the measured output voltages of the DUT 260 from the top voltages and the bottom voltages, the processor 220 may be further operable to determine a measured ratio rmbased on the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the set top voltage and the determined amplitude of a fundamental frequency component of the recorded plurality of measurements of the bottom voltage. This may be achieved in accordance with the formulas given above.

[0072] FIG. 5 is a graph illustrating an exemplary linear fit to a set of measurement ratios, according to some embodiments of the disclosure. There is shown a top voltage (normalized w.r.t. the input range of the DUT 260, for example, the input voltage range of an analog-to- digital converter) on the horizontal axis 502, and associated measured rm=i.e., as a function of the top voltage, on the vertical axis 504. The set of measured ratios rmmay be indicated by the solid circles 506.

[0073] From this, the processor 220 may be further operable to determine a first coefficient b and a second coefficient d based on a best fit of a model equation (given in Eq. 1 ) above to the set of measured ratios rm. Each of the measured ratios may be associated with a corresponding one of the plurality of top voltages, as described above.

[0074] In some embodiments, the processor may be operable to determine the best fit of the model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach,a root mean squared error approach, a minimum variance approach, an R-squared approach, or any other model fitting approach.

[0075] Further, the system 200 may be configured to determine integral nonlinearity of a DUT 260 based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at the DUT 260 at the processor 220, as described above.

[0076] The present disclosure comprises reference to certain examples; however, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the disclosure. In addition, modifications may be made to the disclosed examples without departing from the scope of the present disclosure. Therefore, it is intended that the present disclosure not be limited to the examples disclosed, but that the disclosure will comprise all examples falling within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method to determine integral nonlinearity of a device-under-test, said method comprising setting a top voltage, for each of a plurality of top voltages: balancing a measurement setup; selectively coupling said set top voltage to said DUT; recording a plurality of measurements of said set top voltage by said DUT over a first measurement time period; determining an amplitude of a fundamental frequency component of said recorded plurality of measurements of said set top voltage; selectively coupling a bottom voltage to said DUT; recording a plurality of measurements of said bottom voltage by said DUT over a second measurement time period; determining an amplitude of a fundamental frequency component of said recorded plurality of measurements of said bottom voltage; determining a measured ratio based on said determined amplitude of a fundamental frequency component of said recorded plurality of measurements of said set top voltage and said determined amplitude of a fundamental frequency component of said recorded plurality of measurements of said bottom voltage; and determining a best fit of a model equation to said set of measured ratios, wherein each of said measured ratios is associated with a corresponding one of said plurality of top voltages.

2. The method of claim 1 , comprising determining integral nonlinearity of said DUT based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at said DUT.

3. The method of claim 1 , wherein said measurement setup is an impedance bridge or a Wheatstone bridge.

4. The method of claim 1 , wherein said measurement setup comprises a plurality of voltage sources.

5. The method of claim 1 , wherein said measurement setup comprises two impedance standards.

6. The method of claim 5, wherein said two impedance standards are voltage-stable.

7. The method of claim 5 or claim 6, wherein said two impedance standards are characterized by an impedance ratio of 1 / n.

8. The method of claim 1 , comprising using a multiplexer to selectively couple said set top voltage or said bottom voltage to said DUT.

9. The method of claim 1 , wherein said DUT is an analog-to-digital converter.

10. The method of claim 1 , wherein said set top voltage is a sinusoidal voltage signal.11 . The method of claim 1 , wherein said first measurement time period is substantially equal to said second measurement time period.

12. The method of claim 1 , comprising determining fundamental frequency components using a discrete Fourier transform.

13. The method of claim 1 , wherein said model equation is defined as-14. The method of claim 1 , comprising determining said best fit of said model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach, a root mean squared error approach, a minimum variance approach, an R-squared approach, or any other model fitting approach.

15. The method of claim 1 , comprising balancing said measurement setup by adjusting an auxiliary voltage to zero a difference voltage.

16. The method of claim 1 , comprising selecting each of said plurality of top voltages between 10% to 100% of the input voltage range of said DUT.

17. A system to determine integral nonlinearity of a device-under-test (DUT), said system comprising a measurement setup, comprising: a voltage source to set a top voltage; a multiplexer to selectively couple said set top voltage to said DUT or to selectively couple a bottom voltage to said DUT;a processor operable to record a plurality of measurements of said set top voltage by said DUT over a first measurement time period; wherein said processor is operable to determine an amplitude of a fundamental frequency component of said recorded plurality of measurements of said set top voltage; wherein said processor is further operable to record a plurality of measurements of said bottom voltage by said DUT over a second measurement time period; wherein said processor is further operable to determine an amplitude of a fundamental frequency component of said recorded plurality of measurements of said bottom voltage; wherein said processor is further operable to determine a measured ratio based on said determined amplitude of a fundamental frequency component of said recorded plurality of measurements of said set top voltage and said determined amplitude of a fundamental frequency component of said recorded plurality of measurements of said bottom voltage; and wherein said processor is further operable to determine a best fit of a model equation to said set of measured ratios, wherein each of said measured ratios is associated with a corresponding one of said plurality of top voltages.

18. The system of claim 17, configured to determine integral nonlinearity of said DUT based on an amplitude difference between an input voltage fundamental frequency and an output voltage fundamental frequency at said DUT at said processor.

19. The system of claim 17, wherein said measurement setup is an impedance bridge or a Wheatstone bridge.

20. The system of claim 17, wherein said measurement setup further comprises an auxiliary voltage source, operable to balance said measurement setup.21 . The system of claim 17, wherein said measurement setup comprises two impedance standards.

22. The system of claim 21 , wherein said two impedance standards are voltage-stable.

23. The system of claim claim 21 or claim 22, wherein said two impedance standards are characterized by an impedance ratio of 1 / n.

24. The system of claim 17, wherein said DUT is an analog-to-digital converter.1625. The system of claim 17, wherein said set top voltage is a sinusoidal voltage signal.

26. The system of claim 17, wherein said first measurement time period is substantially equal to said second measurement time period.

27. The system of claim 17, wherein said processor is operable to determine fundamental frequency components using a discrete Fourier transform.

28. The system of claim 17, wherein said model equation is defined as rm®29. The system of claim 17, wherein said processor is operable to determine said best fit of said model equation based on a least-squares approach, a maximum likelihood approach, a minimum mean square error approach, a Bayesian inference approach, a minimum distance approach, a regression approach, a regularization approach, a mean absolute error approach, a root mean squared error approach, a minimum variance approach, an R- squared approach, or any other model fitting approach.

30. The system of claim 17, further comprising a difference voltage measurement device operable to balance said measurement setup by adjusting an adjusting an auxiliary voltage to zero a difference voltage measured by said difference voltage measurement device.31 . The system of claim 17, wherein at said voltage source each of said plurality of top voltages is selected between 10% to 100% of the input voltage range of said DUT.17

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