Impedance calibration device and calibration method

Abstract

The application relates to the field of microelectronics, and discloses an impedance calibration device and a calibration method.The impedance calibration device comprises a circuit board, an impedance line and a characteristic impedance; a first contact point is arranged on the copper surface of the circuit board; the impedance line is arranged on the circuit board; a second contact point and a third contact point are arranged on the impedance line; and one of the characteristic impedances is arranged at the two ends of the impedance line. One signal needle of a probe is stuck on the second contact point, and the other signal needle is stuck on the third contact point, so that differential impedance calibration is realized; one signal needle of the probe is stuck on the first contact point, and the other signal needle is stuck on the second contact point or the third contact point, so that single-end impedance calibration is realized; one device realizes two operations of differential impedance calibration and single-end impedance calibration, and can perform impedance testing on the in-circuit impedance line. The impedance calibration device provided by the application solves the problem that the existing board-edge impedance line testing mode cannot perform impedance testing and calibration on the in-circuit line.

Description

Technical Field

[0001] This invention relates to the field of microelectronics technology, and more specifically to an impedance calibration device and calibration method. Background Technology

[0002] Impedance testing is a commonly used method in electrical engineering and electronics to evaluate the response of circuits, equipment, or systems to AC signals. Before impedance testing, the system error of the impedance testing machine needs to be calibrated. This involves measuring the resistance of an air bar with a specific resistance value calibrated by a metrology certification body, obtaining the deviation value, and then correcting the error to ensure the accuracy of the impedance test.

[0003] In the current technology, the calibration of PCB line characteristic impedance is still limited to the design impedance lines on the board edge, and is conducted manually by staff holding the test head to touch the test point.

[0004] However, the impedance of the PCB board's internal circuitry deviates significantly from the impedance of the impedance lines. For high-end PCBs, impedance testing of the internal circuitry is required, so this method of testing the impedance lines on the board edge cannot meet the requirements. Summary of the Invention

[0005] This invention provides an impedance calibration device and calibration method to solve the problem that the existing board edge impedance line testing method cannot perform impedance testing and calibration of lines inside the board.

[0006] In a first aspect, the present invention provides an impedance calibration device, comprising: a circuit board, an impedance line, and a characteristic impedance, wherein a first contact is disposed on the copper surface of the circuit board; the impedance line is disposed on the circuit board, the impedance line having two segments disposed opposite to each other, and a second contact and a third contact are respectively disposed at the ends of the two segments of the impedance line that are close to each other; and a characteristic impedance is respectively disposed at the ends of the two segments of the impedance line that are far apart from each other.

[0007] Beneficial effects: In use, differential impedance calibration is achieved by placing one signal probe at the second contact and the other at the third contact. The differential impedance is the sum of the specified resistance values ​​of the two characteristic impedances. Single-ended impedance calibration is achieved by placing one signal probe at the first contact and the other at the second or third contact. The single-ended impedance is calibrated to the specified resistance value of a single characteristic impedance. This device performs both differential impedance calibration and single-ended impedance calibration, enabling impedance testing and calibration of lines within the board. The impedance calibration device provided by this invention solves the problem that existing methods for testing impedance lines at the board edge cannot perform impedance testing and calibration of lines within the board.

[0008] In one optional embodiment, the circuit board is provided with a plurality of test areas, each of the test areas being provided with the impedance line and the characteristic impedance, and the characteristic impedance in at least two of the test areas being set with different specification resistance values.

[0009] Beneficial effects: By selecting different characteristic impedances in multiple test areas, impedance calibration with multiple impedance values ​​can be achieved, thus improving the applicability of the device.

[0010] In one optional embodiment, four test areas are provided on the circuit board, and the characteristic impedance in each of the four test areas is set to a different specification value, wherein the specification value of the characteristic impedance is set to 25 ohms to 100 ohms.

[0011] Beneficial effects: By setting characteristic impedances with different specifications in four different test areas, differential and single-ended impedance calibrations with different impedance specifications can be achieved. For example, the specified resistance values ​​of the characteristic impedances in the four test areas are 25 ohms, 50 ohms, 75 ohms, and 100 ohms, respectively. When the probe signal pin is attached to the second and third contacts, the corresponding differential impedances are 50 ohms, 100 ohms, 150 ohms, and 200 ohms; when the probe signal pin is attached to the first and second contacts, or the first and third contacts, the corresponding single-ended impedances are 25 ohms, 50 ohms, 75 ohms, and 100 ohms, thus realizing impedance calibration with multiple impedance specifications.

[0012] In one alternative embodiment, the two impedance lines are at least partially parallel and spaced apart, with the distance between the parallel portions of the two impedance lines being 0.2 mm to 6 mm.

[0013] Beneficial effect: The two impedance lines are set parallel to each other with at least a partial gap of 0.2mm to 6mm, which helps to ensure the accuracy of the test.

[0014] In one alternative embodiment, the first contact is disposed on the copper surface of the circuit board surrounded by the inner sides of the two impedance lines.

[0015] Beneficial effect: The first contact is located inside the two impedance lines, which makes it convenient for one signal probe to be inserted into the first contact and the other signal probe to be inserted into the second or third contact, so as to realize single-ended impedance calibration.

[0016] In one alternative embodiment, the two impedance lines form a U-shaped structure, and the second contact and the third contact are located at the midpoint of the U-shaped structure formed by the impedance lines.

[0017] Beneficial effects: The two impedance lines are arranged in a U-shape, which ensures the minimum spacing between the second and third contacts, making it convenient for one signal probe to be inserted into the second contact and the other signal probe into the third contact, thus achieving differential impedance calibration; the second and third contacts are equidistant from the ends of the impedance lines, which ensures that the single-ended impedance calibration impedance values ​​of the second and third contacts inserted into the same test area are the same.

[0018] In one alternative implementation, the characteristic impedance is set as an air bar.

[0019] Beneficial effects: The use of air bars can help users ensure the reliability of test results and avoid inaccurate test results due to instrument errors and deviations.

[0020] Secondly, the present invention also provides a calibration method, employing the impedance calibration device described in the above embodiments, comprising the following steps:

[0021] Differential impedance calibration: one signal pin on the probe contacts the second contact on the impedance line, and the other signal pin on the probe contacts the third contact on the impedance line.

[0022] For single-ended impedance calibration, one signal pin on the probe contacts the first contact on the copper surface of the circuit board, and the other signal pin on the probe contacts the second or third contact on the impedance line.

[0023] Beneficial effects: A single device can simultaneously perform differential impedance calibration and single-ended impedance calibration, and can also measure the impedance within the board at the same time.

[0024] In one optional implementation, the probe performs single-ended impedance calibration and differential impedance calibration on each test area on the circuit board, and collects the test results of the probe each time as the original measurement value. The original measurement value and the known standard value are combined to establish a calibration data pair. The characteristic impedance adopts a standard air rod sample, and the known standard value is the impedance value composed of the characteristic impedance corresponding to the original measurement value.

[0025] Using a 5Ω span as the standard for segmentation, the range of 10Ω-120Ω is divided into several levels;

[0026] For each gear, a first-order linear least squares fit is performed using the calibration data points that fall within that interval, and the fitting results are stored in the form of a lookup table.

[0027] When the probe's test value falls in the middle region of the gear range, the compensation coefficient of the current gear is taken, and the compensation impedance value is obtained by inverse transformation.

[0028] When the probe's test value falls near the boundary of the gear range, the compensation coefficients of two adjacent gears are taken. An interpolation compensation algorithm is used to obtain the interpolation compensation coefficient based on the weighted interpolation. The inverse transformation is then used to obtain the compensated impedance value.

[0029] Beneficial effects: The impedance range of 10Ω to 120Ω covers the main design impedance range of high-speed signal lines on circuit boards, with each segment spanning 5Ω, achieving a balance between accuracy and computational complexity. Using a standard air rod sample as the characteristic impedance, the aforementioned impedance calibration device generates multiple impedance values ​​as known standard values. The test results of each probe are collected as the raw measurement values. Calibration data pairs are established between the raw measurement values ​​and the known standard values. Based on the calibration data points falling within the corresponding range, a first-order linear least-squares fit is performed, and the fitting results are stored in a lookup table. When the probe's test value falls in the middle region of the range, the compensation coefficients from the lookup table are directly used for inverse transformation. When the probe's test value falls near the boundary of the range, an interpolation compensation algorithm is used to obtain interpolation compensation coefficients for inverse transformation, thereby obtaining the compensated impedance value and improving the probe's testing accuracy. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of an impedance calibration device according to an embodiment of the present invention;

[0032] Figure 2 for Figure 1 A schematic diagram of the back of the impedance calibration device is shown.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Circuit board; 2. Impedance lines; 3. Mounting holes; 4. First contact; 5. Second contact; 6. Third contact; 7. Test area. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The following is combined with Figures 1 to 2 The following describes embodiments of the present invention.

[0037] According to an embodiment of the present invention, an impedance calibration device is provided, comprising: a circuit board 1, an impedance line 2, and a characteristic impedance. A first contact 4 is disposed on the copper surface of the circuit board 1; the impedance line 2 is disposed on the circuit board 1, and the impedance line 2 has two segments disposed opposite to each other. A second contact 5 and a third contact 6 are respectively disposed at the ends of the two segments of the impedance line 2 that are close to each other; and a characteristic impedance is respectively disposed at the ends of the two segments of the impedance line 2 that are far apart from each other.

[0038] In use, differential impedance calibration is achieved by placing one signal probe at the second contact 5 and the other signal probe at the third contact 6. The differential impedance is the sum of the specified resistance values ​​of the two characteristic impedances. Single-ended impedance calibration is achieved by placing one signal probe at the first contact 4 and the other signal probe at either the second contact 5 or the third contact 6. The single-ended impedance is the specified resistance value of a single characteristic impedance. This device performs both differential impedance calibration and single-ended impedance calibration, enabling impedance testing and calibration of lines within the board. The impedance calibration device provided in this embodiment solves the problem that existing methods for testing impedance lines at the board edge cannot perform impedance testing and calibration of lines within the board.

[0039] Specifically, the circuit board 1 is provided with mounting holes 3 for mounting the characteristic impedance.

[0040] In one embodiment, the circuit board 1 is provided with multiple test areas 7, each test area 7 containing the impedance line 2 and the characteristic impedance, and the characteristic impedance in at least two of the test areas 7 is set to different specified resistance values. By selecting different characteristic impedances in multiple test areas 7, impedance calibration with multiple specified impedance values ​​can be achieved, improving the applicability of the device. Alternatively, as an alternative implementation, only one test area 7 may be provided on the circuit board 1.

[0041] In one embodiment, four test areas 7 are provided on the circuit board 1, and the characteristic impedances in the four test areas 7 are all set with different specified resistance values, which are set to 25 ohms to 100 ohms. Setting different specified resistance values ​​in the four different test areas 7 enables differential and single-ended impedance calibration with different impedance values. Alternatively, as an alternative implementation, the test areas 7 can be set to two, three, or more as needed.

[0042] Specifically, the characteristic impedance values ​​in the four test areas 7 are preferably 25 ohms, 50 ohms, 75 ohms, and 100 ohms, respectively. When the probe signal pin is positioned between the second contact 5 and the third contact 6, the corresponding differential impedances are 50 ohms, 100 ohms, 150 ohms, and 200 ohms. When the probe signal pin is positioned between the first contact 4 and the second contact 5, or between the first contact 4 and the third contact 6, the corresponding single-ended impedances are 25 ohms, 50 ohms, 75 ohms, and 100 ohms, thus achieving impedance calibration with multiple impedance values.

[0043] In one embodiment, the two impedance lines 2 are at least partially parallel and spaced apart, with the distance between the parallel portions of the two impedance lines 2 being 0.2mm to 6mm. This parallel arrangement of the two impedance lines 2 with at least a 0.2mm to 6mm gap helps ensure test accuracy. Alternatively, as an alternative implementation, when high test accuracy is not required, the impedance lines 2 can also be arranged at an angle.

[0044] In one embodiment, the first contact 4 is disposed on the copper surface of the circuit board 1 surrounded by the inner sides of the two impedance lines 2. The placement of the first contact 4 inside the two impedance lines 2 allows for easy insertion of one signal probe into the first contact 4 and the other signal probe into the second contact 5 or the third contact 6, thus achieving single-ended impedance calibration.

[0045] In one embodiment, the two impedance lines 2 form a U-shaped structure, with the second contact 5 and the third contact 6 positioned at the midpoint of the U-shaped structure. The U-shaped arrangement of the two impedance lines 2 ensures minimal spacing between the second contact 5 and the third contact 6, facilitating differential impedance calibration by having one signal probe inserted into the second contact 5 and the other into the third contact 6. The equal distances of the second contact 5 and the third contact 6 from the ends of the impedance lines 2 ensure that the single-ended impedance calibration values ​​within the same test area 7 are identical. Alternatively, as an alternative embodiment, the two impedance lines 2 can also be two parallel straight lines.

[0046] In one embodiment, the characteristic impedance is set as an air bar. The use of an air bar helps users ensure the reliability of test results and avoids inaccurate results due to instrument errors and deviations.

[0047] According to an embodiment of the present invention, in another aspect, a calibration method is also provided, employing the impedance calibration device described in the above embodiments, comprising the following steps:

[0048] Differential impedance calibration: one signal pin on the probe contacts the second contact 5 on the impedance line 2, and the other signal pin on the probe contacts the third contact 6 on the impedance line 2.

[0049] For single-ended impedance calibration, one signal pin on the probe contacts the first contact 4 on the copper surface of the circuit board 1, and the other signal pin on the probe contacts the second contact 5 or the third contact 6 on the impedance line 2.

[0050] It enables a single device to perform both differential impedance calibration and single-ended impedance calibration, and can simultaneously measure the impedance within the board.

[0051] In one embodiment, the probe performs single-ended impedance calibration and differential impedance calibration on each test area 7 on the circuit board 1, and collects the test results of the probe each time as the original measurement value. The original measurement value and the known standard value are combined to establish a calibration data pair. The characteristic impedance adopts a standard air rod sample, and the known standard value is the impedance value composed of the characteristic impedance corresponding to the original measurement value.

[0052] Using a 5Ω span as the standard for segmentation, the range of 10Ω-120Ω is divided into several levels;

[0053] For each gear, a first-order linear least squares fit is performed using the calibration data points that fall within that interval, and the fitting results are stored in the form of a lookup table.

[0054] When the probe's test value falls in the middle region of the gear range, the compensation coefficient of the current gear is taken, and the compensation impedance value is obtained by inverse transformation.

[0055] When the probe's test value falls near the boundary of the gear range, the compensation coefficients of two adjacent gears are taken. An interpolation compensation algorithm is used to obtain the interpolation compensation coefficient based on the weighted interpolation. The inverse transformation is then used to obtain the compensated impedance value.

[0056] The impedance range of 10Ω to 120Ω covers the main design impedance range of high-speed signal lines on circuit boards, with each segment spanning 5Ω, achieving a balance between accuracy and computational complexity. Using a standard air bar sample as the characteristic impedance, the aforementioned impedance calibration device generates multiple impedance values ​​as known standard values. The test results of each probe are collected as the raw measurement values. Calibration data pairs are established between the raw measurement values ​​and the known standard values. Based on the calibration data points falling within the corresponding range, a first-order linear least-squares fit is performed, and the fitting results are stored in a lookup table. When the probe's test value falls in the middle region of the range, the compensation coefficients from the lookup table are directly used for inverse transformation. When the probe's test value falls near the boundary of the range, an interpolation compensation algorithm is used to obtain interpolation compensation coefficients for inverse transformation, thereby obtaining the compensated impedance value and improving the probe's testing accuracy.

[0057] Specifically, the 10Ω-120Ω range is evenly divided into 22 levels, with each level being 5Ω.

[0058] The calibration data pairs established using the original test values ​​and known standard values ​​are as follows:

[0059]

[0060] Where: R ref，i Given the standard value, R meas，i These are the original measured values.

[0061] For each gear k, the interval is [ , First-order linear least squares fitting is performed using calibration data points falling within this interval:

[0062]

[0063] Least squares solution:

[0064]

[0065]

[0066] This yields the compensation coefficient pair for each gear level. , ), a total of 22 groups.

[0067] The fitting results are stored in the form of a lookup table:

[0068]

[0069] When the probe's test result R x When the gear position falls near the boundary of a certain gear range, directly shifting gears will introduce a step error. To ensure a smooth transition, linear interpolation is used:

[0070] Assuming the value falls between the k-th and (k+1)-th levels, the interpolation weights are:

[0071]

[0072] Interpolation compensation coefficient:

[0073]

[0074]

[0075] Final compensated impedance value:

[0076]

[0077] Where: R xThe value obtained from the test. This represents the upper limit value of the k-th level. This is the lower limit value of the k-th level. R is the upper limit value of the (k+1)th level. meas For the original measurement value, a interp and b interp R is the interpolation compensation coefficient. comp This is the compensated impedance value.

[0078] The specific algorithm flow of the calibration method provided in this embodiment is as follows:

[0079] Input the original measurement value R meas Determine R meas Gear position k.

[0080] If R meas In the middle region of the gear range, directly use LUT[k]'s (a) k b k The inverse transformation yields the compensated impedance value R. comp .

[0081] If R meas Near the boundary of the gear range, take LUT[k] and LUT[k+1], and interpolate according to the weight w to obtain a. interp and b interp The inverse transformation yields the compensated impedance value R. comp .

[0082] Output compensation impedance value R comp .

[0083] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An impedance calibration device, characterized in that, include: Circuit board (1), wherein a first contact (4) is provided on the copper surface of the circuit board (1); Impedance line (2) is provided on the circuit board (1). The impedance line (2) has two segments arranged opposite to each other. The two segments of the impedance line (2) are respectively provided with a second contact (5) and a third contact (6) at their ends that are close to each other. Characteristic impedance is provided at one end of each of the two impedance lines (2) that are far apart from each other; The first contact (4) is located on the copper surface of the circuit board (1) surrounded by the two impedance lines (2); The two impedance lines (2) form a U-shaped structure, and the second contact (5) and the third contact (6) are located at the midpoint of the U-shaped structure formed by the impedance lines (2).

2. The impedance calibration device according to claim 1, characterized in that, The circuit board (1) is provided with multiple test areas (7), and each test area (7) is provided with the impedance line (2) and the characteristic impedance. The characteristic impedance in at least two test areas (7) is set with different resistance values.

3. The impedance calibration device according to claim 2, characterized in that, The test area (7) is provided in four places on the circuit board (1). The characteristic impedance in the four test areas (7) is set to different resistance values. The resistance value of the characteristic impedance is set to 25 ohms to 100 ohms.

4. The impedance calibration device according to claim 1, characterized in that, The two impedance lines (2) are at least partially parallel and spaced apart, and the distance between the parallel portions of the two impedance lines (2) is 0.2mm to 6mm.

5. The impedance calibration device according to any one of claims 1 to 4, characterized in that, The characteristic impedance is set as an air rod.

6. A calibration method, employing the impedance calibration device according to any one of claims 1-5, characterized in that, Includes the following steps: Differential impedance calibration: one signal pin on the probe contacts the second contact (5) on the impedance line (2), and the other signal pin on the probe contacts the third contact (6) on the impedance line (2); For single-ended impedance calibration, one signal pin on the probe contacts the first contact (4) on the copper surface of the circuit board (1), and the other signal pin on the probe contacts the second contact (5) or the third contact (6) on the impedance line (2). The probe performs single-ended impedance calibration and differential impedance calibration on each test area (7) on the circuit board (1). The test results of the probe each time are collected as the original measurement value. The original measurement value and the known standard value are combined to establish a calibration data pair. The characteristic impedance adopts a standard air rod sample. The known standard value is the impedance value composed of the characteristic impedance corresponding to the original measurement value. Using a 5Ω span as the standard for segmentation, the range of 10Ω-120Ω is divided into several levels; For each gear, a first-order linear least squares fit is performed using the calibration data points that fall within the gear range, and the fitting results are stored in the form of a lookup table. When the probe's test value falls in the middle region of the gear range, the compensation coefficient of the current gear is taken, and the compensation impedance value is obtained by inverse transformation. When the probe's test value falls near the boundary of the gear range, the compensation coefficients of two adjacent gears are taken. An interpolation compensation algorithm is used to obtain the interpolation compensation coefficient based on the weighted interpolation. The inverse transformation is then used to obtain the compensated impedance value.

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