Temperature compensation information export method

Abstract

To provide an AD conversion device that can comprehensively reduce temperature dependence of the entire device.SOLUTION: An AD conversion device 1 (analog-digital conversion device) that converts analog input potential into digital AD conversion result (analog-digital conversion result), a reference potential generation circuit 3 that generates a reference potential, an analog-to-digital converter 2 that converts an input potential into a digital value using the reference potential, a temperature correction calculator 8 that calculates a temperature correction value using a temperature error function that calculates an error from the temperature, and an adder 10 that outputs a value obtained by adding the temperature correction value calculated by the temperature correction calculator 8 to the digital value converted by the analog-to-digital converter 2 as an AD conversion result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an analog-to-digital converter that converts an input analog signal into a digital value. This also relates to a method for deriving temperature compensation information. [Background technology]

[0002] In the field of PMICs (Power Management ICs: ICs equipped with multiple DC-DC converters and LDOs that can communicate with a CPU to flexibly change power supply control) for automotive equipment, there is a demand for high-speed, high-precision analog-to-digital converters (hereinafter referred to as AD converters). Such AD converters must correct errors arising from variations in constituent elements due to the manufacturing process without compromising high speed (see, for example, Patent Document 1).

[0003] Circuit types used in high-speed, high-precision AD converters include successive approximation AD converters, flash AD converters, and pipeline AD converters. In all of these circuit types, the AD converter requires a reference potential as the reference for conversion. The reference potential is the reference point when converting an analog input to a digital value, and can be likened to a ruler of length. If the reference ruler (reference potential) becomes long (the reference potential becomes high), the object being measured (the analog potential being converted) will be measured as short (the potential will appear low). Conversely, if the ruler (reference potential) becomes short (the reference potential becomes low), it will be measured as longer than it actually is (the potential will appear high).

[0004] Thus, the reference potential must be accurate. Therefore, a bandgap circuit utilizing diode characteristics is generally used to generate the reference potential of semiconductors. A bandgap circuit can obtain a stable, constant potential even when variations occur in the elements during the manufacturing process. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2022 / 102002 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, bandgap circuits exhibit temperature variations (temperature dependence). Generally, this temperature dependence is mitigated using a temperature compensation circuit that combines a resistor with a positive temperature dependence with a resistor with a negative temperature dependence. However, even with a temperature compensation circuit, the temperature dependence of a bandgap circuit cannot be completely eliminated and remains as a small residual error.

[0007] In the field of PMICs for automotive equipment, where high speed and high precision are required, AD converters must be able to withstand changes in the temperature environment, and the temperature dependence of the bandgap circuit becomes a problem. For example, in an AD converter with a resolution of 12 bits (0 to 4095) and an input potential range (dynamic range) of 1V, the potential corresponding to each resolution unit is only 0.24mV. It is not easy to realize a near-ideal reference potential generation circuit that meets the requirements of such a high-precision AD converter using only a combination of analog circuits. Furthermore, doing so would require the creation of large-scale and complex circuits, resulting in high manufacturing costs. This is a major problem in terms of product pricing. This temperature dependence problem exists not only in the bandgap circuit but also in the gain amplifier and the AD converter.

[0008] This invention was made in view of the aforementioned problems, and its objective is to provide an AD conversion device that can comprehensively reduce temperature dependence as a whole. [Means for solving the problem]

[0009] According to the present invention Temperature compensation information derivation methodIn order to achieve the above object, it is configured as follows. The one according to the present invention Temperature compensation information derivation method is an analog-to-digital conversion device that converts an analog input potential into a digital analog-to-digital conversion result, and includes a reference potential generation circuit that generates a reference potential, an analog-to-digital converter that converts the input potential into a digital value using the reference potential, a temperature correction calculator that calculates a temperature correction value using a temperature error function that obtains an error from temperature, and an adder that outputs, as the analog-to-digital conversion result, a value obtained by adding the temperature correction value calculated by the temperature correction calculator to the digital value converted by the analog-to-digital converter. A method for deriving temperature compensation information for deriving the temperature characteristic parameter value of the temperature error function used in an analog-to-digital conversion device during a product inspection process, wherein the temperature characteristic parameter value is derived using the errors of the analog-to-digital conversion results for at least three temperature conditions, while the error values ​​of the analog-to-digital conversion results for two input potentials are the same. It is characterized by this.

Advantages of the Invention

[0010] The present invention has the effect of being able to comprehensively reduce the temperature dependence of the entire device and providing a high-speed and high-precision AD conversion device with low temperature dependence at a reduced manufacturing cost.

Brief Description of the Drawings

[0011] [Figure 1] It is a block diagram showing the configuration of an embodiment of an analog-to-digital conversion device according to the present invention. [Figure 2] It is a diagram showing the conversion characteristics of the AD converter shown in FIG. 1. [Figure 3] It is a diagram showing the conversion characteristics of the AD converter shown in FIG. 1. [Figure 4] It is a diagram showing the output characteristics of the bandgap circuit shown in FIG. 1. [Figure 5] It is a diagram for explaining temperature compensation in the reference potential generation circuit shown in FIG. 1. [Figure 6] It is a diagram for explaining the operation of the temperature correction calculator shown in FIG. 1. [Figure 7] It is a diagram showing a modification example of the analog-to-digital conversion device shown in FIG. 1. [Figure 8] It is a block diagram showing the configuration of a product inspection device used in the product inspection process. [Figure 9]This is a flowchart showing the product inspection process at a high-temperature setting. [Figure 10] This flowchart shows the product inspection process at a low set temperature. [Figure 11] This is a flowchart showing the product inspection process at a medium temperature setting. [Figure 12] This diagram illustrates the relationship between error and reference potential. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

[0013] The AD (analog-to-digital) converter 1 of this embodiment (hereinafter, analog-to-digital is referred to as AD) comprises, as shown in Figure 1, an AD converter 2, a reference potential generation circuit 3, a slope trimming value memory 4, a gain trimming value memory 5, a temperature sensor 6, a temperature characteristic parameter value memory 7, a temperature compensation calculator 8, a temperature compensation value register 9, and an adder 10.

[0014] The AD converter 2 is a high-speed AD converter such as a successive approximation AD converter, flash AD converter, or pipeline AD converter, which requires a reference potential for its conversion. It uses the reference potential generated by the reference potential generation circuit 3 to convert the analog input potential input to the input terminal Tin into a digital value.

[0015] As shown in Figure 2(a), the AD converter 2 converts the input potential a to a digital value A, assuming that the reference potential generated by the reference potential generation circuit 3 is appropriate. Therefore, if the reference potential generated by the reference potential generation circuit 3 is lower than the appropriate value, the AD converter 2 converts the input potential a to a digital value A+B that is larger than digital value A. This error B increases as the input potential a increases. Conversely, if the reference potential generated by the reference potential generation circuit 3 is higher than the appropriate value, the AD converter 2 converts the input potential a to a digital value AC that is smaller than digital value A. This error C increases as the input potential a increases.

[0016] As shown in Figure 2(b), the AD converter 2 converts the input potential a' to a digital value A' with ideal characteristics, assuming that the constituent elements are temperature-independent. Therefore, if there is a positive offset error due to temperature fluctuations, the AD converter 2 converts the input potential a' to a digital value A'+B' which is larger than the digital value A'. This error B' is constant regardless of the input potential a'. Conversely, if there is a negative offset error due to temperature fluctuations, the AD converter 2 converts the input potential a' to a digital value A'-C' which is smaller than the digital value A'. This error C' is constant regardless of the input potential a'.

[0017] Thus, as shown in Figure 3, the output characteristics of the AD converter 2 have errors due to offset and errors due to fluctuations in the reference potential. The dashed line in Figure 3 represents the output characteristics when there is a positive offset error due to temperature fluctuations and the reference potential generated by the reference potential generation circuit 3 is lower than the appropriate value.

[0018] The reference potential generation circuit 3 comprises a bandgap circuit 31, a slope trimming unit 32, a gain amplifier 33, and a gain trimming unit 34.

[0019] The bandgap circuit 31 is a potential generation circuit that utilizes the bandgap potential of a semiconductor. The bandgap circuit 31 incorporates a temperature compensation circuit that combines a resistor that has a positive dependence on temperature (hereinafter referred to as a positive-dependent resistor) and a resistor that has a negative dependence on temperature (hereinafter referred to as a negative-dependent resistor). As shown in Figure 4, the temperature output characteristics (temperature dependence) of the bandgap circuit 31 are reduced by the effects of the positive-dependent resistor and the negative-dependent resistor.

[0020] The bandgap circuit 31 is configured to allow the slope of the temperature output characteristic to be changed. For example, in the bandgap circuit 31, at least one of the positive-dependent resistor and the negative-dependent resistor is configured as a variable resistor. The variable resistor is configured, for example, as a series circuit in which multiple resistors are connected in series, and the number of resistors used can be set.

[0021] The tilt trimming unit 32 sets the temperature output characteristics of the bandgap circuit 31 to the same output potential at the high-temperature set temperature X and the low-temperature set temperature Y, as shown in Figure 5(a), based on the tilt trimming value stored in the tilt trimming value memory 4, which is a non-volatile memory. There are no particular restrictions on the high-temperature set temperature X and the low-temperature set temperature Y, as long as there is a certain distance (temperature difference) between them, but it is preferable to set them near the lower limit and upper limit of the operating temperature of the AD converter 1, respectively.

[0022] The slope trimming unit 32 sets the resistance value of a positive-dependent or negative-dependent resistor, which is composed of a variable resistor, based on the slope trimming value, so that the output potential is equal at the high-temperature set temperature X and the low-temperature set temperature Y. In other words, the slope trimming value in the slope trimming value memory 4 is a value used to set the temperature output characteristics of the bandgap circuit 31 so that the output potential is equal at the high-temperature set temperature X and the low-temperature set temperature Y. If the variable resistor (positive-dependent or negative-dependent resistor) is a series circuit in which multiple resistors are connected in series, the slope trimming value is a value that sets the number of resistors to be used. In this case, since the resistance value of the positive-dependent or negative-dependent resistor is set in steps, the bandgap circuit 31 is set to a temperature output characteristic in which the output potential can be considered equal at the high-temperature set temperature X and the low-temperature set temperature Y.

[0023] The temperature output characteristics of the bandgap circuit 31, set by the slope trimming of the slope trimming unit 32, are relative values, and the absolute value is not important. In other words, the output potential of the bandgap circuit 31 does not need to be the target reference potential output requested by the reference potential generation circuit 3.

[0024] The gain amplifier 33 outputs a reference potential to the AD converter 2, which is obtained by amplifying or attenuating the output potential of the bandgap circuit 31. The gain amplifier 33 is configured to allow the gain (amplification factor) to be changed, for example, by using a variable resistor in the negative feedback path of the operational amplifier. The variable resistor is configured, for example, in a series circuit in which multiple resistors are connected in series, and the number of resistors used can be set.

[0025] The gain trimming unit 34, based on the gain trimming values ​​stored in the gain trimming value memory 5, which is a non-volatile memory, sets the gain of the gain amplifier 33 to a gain that amplifies or attenuates the output potential of the bandgap circuit 31 at the high-temperature set temperature X and low-temperature set temperature Y to the target reference potential, as shown in Figure 5(b).

[0026] The gain trimming unit 34 sets the gain of the bandgap circuit 31 by setting the resistance value of the variable resistor in the negative feedback path based on the gain trimming value. In other words, the gain trimming value in the gain trimming value memory 5 is a value used to set the gain of the gain amplifier 33 to amplify or attenuate the output potential of the bandgap circuit 31 at the high temperature setting temperature X and the low temperature setting temperature Y to the target reference potential. If the variable resistor in the negative feedback path is a series circuit with multiple resistors connected in series, the gain trimming value is a value that sets the number of resistors to be used. In this case, since the variable resistor in the negative feedback path is set in steps, the gain amplifier 33 will be set to a gain that amplifies or attenuates the output potential of the bandgap circuit 31 at the high temperature setting temperature X and the low temperature setting temperature Y to a potential that can be considered the target reference potential.

[0027] The temperature sensor 6 measures the ambient temperature and outputs a digital temperature value that has a linear correlation with the measured temperature. The temperature sensor 6 includes a forward voltage generation circuit 61 that utilizes the fact that the forward voltage when a constant current is passed through a diode is almost linear with respect to temperature, and a temperature sensor AD converter 62 that converts the forward voltage generated by the forward voltage generation circuit 61 into a digital temperature value.

[0028] The temperature characteristic parameter value memory 7 is a non-volatile memory, and stores the temperature characteristic parameter values of the AD converter 2 and the reference potential generation circuit 3 combined. The temperature characteristic parameter value is a parameter value of a calculation formula for calculating an approximation error based on the temperature digital value. In the present embodiment, as shown in FIG. 6, the temperature characteristic parameter value is the parameter value (coefficient α XZ , constant term β XZ ) of the first linear approximation formula set based on the error at the high temperature set temperature X and the error at the medium temperature set temperature Z (X < Z < Y), and the parameter value (coefficient α ZY , constant term β ZY ) of the second linear approximation formula set based on the error at the medium temperature set temperature Z and the error at the low temperature set temperature Y. The medium temperature set temperature Z may be set in advance in the temperature correction calculator 8, or may be included in the temperature characteristic parameter value. Also, two or more medium temperature set temperatures Z may be set, and the temperature characteristic parameter value may be the parameter value of each of three or more linear approximation formulas.

[0029] The temperature correction calculator 8 calculates an approximation error from the temperature digital value output from the temperature sensor 6 and the temperature characteristic parameter value stored in the temperature characteristic parameter value memory 7, and outputs the reciprocal of the calculated approximation error as a temperature correction value. In the present embodiment, when the temperature digital value #Z (medium temperature set temperature Z) or higher, the temperature correction calculator 8 calculates the approximation error using the first linear approximation formula (coefficient α XZ , constant term β XZ ), and when the temperature digital value #Z (medium temperature set temperature Z) is less than, calculates the approximation error using the second linear approximation formula (coefficient α ZY , constant term β ZY ).

[0030] The calculation frequency of the approximation error (output frequency of the temperature correction value) by the temperature correction calculator 8 can be set as appropriate. The temperature correction calculator 8 may calculate the approximation error (output the temperature correction value) at a preset time interval (for example, 1 second), for example. Also, the temperature correction calculator 8 may calculate the approximation error (output the temperature correction value) when the amount of change in the temperature digital value becomes a predetermined value or more set in advance.

[0031] The temperature compensation value register 9 temporarily stores the temperature compensation value output from the temperature compensation calculator 8. The contents of the temperature compensation value register 9 are overwritten each time the temperature compensation value output from the temperature compensation calculator 8 is updated.

[0032] The adder 10 adds the digital value output by the AD converter 2 with the temperature compensation value stored in the temperature compensation value register 9 and outputs the result from the output terminal Tout as a temperature-compensated, high-precision AD conversion result.

[0033] The AD converter 2 operates independently of the temperature sensor 6 and the temperature compensation calculator 8, and does not need to wait for the above-mentioned temperature compensation value to be generated.

[0034] Furthermore, if the accuracy of the reference potential generated by the reference potential generation circuit 3 is high, the slope trimming unit 32, slope trimming value memory 4, gain trimming unit 34, and gain trimming value memory 5 can be omitted, and comprehensive temperature compensation can be performed using only the temperature characteristic parameter values ​​in the temperature characteristic parameter value memory 7.

[0035] Furthermore, if the temperature dependence of the bandgap circuit 31 is within an acceptable range, the slope trimming unit 32 and the slope trimming value memory 4 can be omitted, and comprehensive temperature compensation can be performed using the gain trimming value in the gain trimming value memory 5 and the temperature parameter value in the temperature characteristic parameter value memory 7.

[0036] Automotive PMICs require multiple AD conversion processes and therefore incorporate multiple AD converters 1. As shown in Figure 7(a), when multiple AD converters 1a to 1c are provided, each AD converter 1a to 1c is equipped with a temperature input terminal T3, and a digital temperature value input from an externally provided temperature sensor 6 may be used. Alternatively, as shown in Figure 7(b), when multiple AD converters 1a to 1d are provided, and AD converter 1d is equipped with a temperature sensor 6, each AD converter 1a to 1c is equipped with a temperature input terminal T3, and AD converter 1d is equipped with a temperature output terminal T1, and AD converters 1a to 1c may use the digital temperature value output from AD converter 1d.

[0037] The slope trimming value, gain trimming value, and temperature characteristic parameter value are derived during the product inspection process and stored in the slope trimming value memory 4, the gain trimming value memory 5, and the temperature characteristic parameter value memory 7, respectively. Note that the slope trimming value memory 4, the gain trimming value memory 5, and the temperature characteristic parameter value memory 7 do not need to be physically separate; a common non-volatile memory can be used.

[0038] The temperature compensation information, including the slope trimming value, gain trimming value, and temperature characteristic parameter value, is derived using the temperature compensation information derivation method with respect to the product inspection device 100. The product inspection device 100 and the temperature compensation information derivation method will be described in detail below with reference to Figures 8 to 12.

[0039] Referring to Figure 8, the product inspection device 100 includes an input potential generation circuit 110, a target conversion result storage unit 120, an AD conversion result receiving unit 130, a temperature digital value receiving unit 140, and a control unit 150.

[0040] The input potential generation circuit 110 has the function of generating "first input potential a1" and "second input potential a2" as two different input potentials within the input potential range of the AD converter 1, and inputs either the specified "first input potential a1" or "second input potential a2" to the input terminal Tin of the AD converter 1.

[0041] The target conversion result storage unit 120 is a non-volatile storage means and stores the "target conversion result A1" for the "first input potential a1" and the "target conversion result A2" for the "second input potential a2".

[0042] The AD conversion result receiving unit 130 is an interface that receives input of the AD conversion result output from the output terminal Tout of the AD conversion device 1.

[0043] The temperature digital value receiving unit 140 is an interface that receives input of the temperature digital value output from the temperature output terminal T1 of the AD converter 1.

[0044] The control unit 150 is an arithmetic processing circuit such as a microcomputer equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The ROM stores a control program for controlling the operation of the product inspection device 100. The control unit 150 reads the control program stored in the ROM and loads the control program into the RAM, thereby functioning as a measurement condition setting unit 151, an error calculation unit 152, and a temperature compensation information derivation unit 153.

[0045] The product inspection process is carried out at a high temperature setting X, a low temperature setting Y, and a medium temperature setting Z, which is between the high temperature setting X and the low temperature setting Y. The order in which the product inspection process is carried out is that the high temperature setting X or low temperature setting Y is performed first, and the medium temperature setting Z is performed last. This embodiment shows an example in which the process is carried out in the order of high temperature setting X, low temperature setting Y, and medium temperature setting Z.

[0046] Furthermore, during the product inspection process, the AD converter 1 is configured to stop the operation of the temperature compensation calculator 8, the temperature compensation value register 9, and the adder 10, and to output the digital value output by the AD converter 2 as the AD conversion result.

[0047] (Product inspection process at high-temperature setting X: Figure 9) (1) The measurement condition setting unit 151 writes the slope trimming value set to an arbitrary value θ to the slope trimming value memory 4 via the data input terminal T2 and fixes it.

[0048] (2) The measurement condition setting unit 151 updates the gain trimming value by writing the successively changed gain trimming value to the gain trimming value memory 5 from the data input terminal T2. The error calculation unit 152 calculates the error a1 at the "first input potential a1" and the error a2 at the "second input potential a2" each time the gain trimming value is updated, and identifies the gain trimming value at which the two match (the smallest possible match). Error a1 is the error between the AD conversion result input to the AD conversion result receiving unit 130 when the input potential of the input potential generation circuit 110 is specified as the "first input potential a1", and the "target conversion result A1". Error a2 is the error between the AD conversion result input to the AD conversion result receiving unit 130 when the input potential of the input potential generation circuit 110 is specified as the "second input potential a2", and the "target conversion result A2".

[0049] (3) The error calculation unit 152 temporarily stores the error a1 (or error a2) at the slope trimming value θ and the gain trimming value specified in (2) as "error #X" under the condition of "appropriate reference potential". The error calculation unit 152 also temporarily stores the temperature digital value at the high-temperature set temperature X as "temperature digital value #X". Note that there are no particular restrictions on where the data of the derivation process, such as "error #X" and "temperature digital value #X", is temporarily stored; for example, it can be temporarily stored in the RAM of the control unit 150.

[0050] (4) The measurement condition setting unit 151 writes the gain trimming value set to an arbitrary value η to the gain trimming value memory 5 via the data input terminal T2 and fixes it.

[0051] (5) The measurement condition setting unit 151 updates the slope trimming value by writing the sequentially changed slope trimming value to the slope trimming value memory 4 from the data input terminal T2. The error calculation unit 152 calculates the difference (error a1 - error a2) between the error a1 at the "first input potential a1" and the error a2 at the "second input potential a2" each time the slope trimming value is updated. The error calculation unit 152 then temporarily stores the numerical array of the error difference (error a1 - error a2) for each slope trimming value as "error array #X[slope trimming value]" and terminates the product inspection process at the high temperature setting temperature X.

[0052] (Product inspection process at low temperature setting Y: Figure 10) Similar to (6) and (4), the measurement condition setting unit 151 writes the gain trimming value set to an arbitrary value η to the gain trimming value memory 5 via the data input terminal T2 and fixes it.

[0053] (7) The measurement condition setting unit 151 updates the slope trimming value by writing the sequentially changed slope trimming value to the slope trimming value memory 4 from the data input terminal T2. The error calculation unit 152 calculates the difference (error a1 - error a2) between the error a1 at the "first input potential a1" and the error a2 at the "second input potential a2" each time the slope trimming value is updated. The error calculation unit 152 then temporarily stores a numerical array of the error difference (error a1 - error a2) for each slope trimming value as "error array #Y[slope trimming value]".

[0054] (8) The temperature compensation information derivation unit 153 compares the numerical array from (5) as error array #X [slope trimming value] and error array #Y [slope trimming value] from (7). The temperature compensation information derivation unit 153 identifies the slope trimming value that makes the difference in errors of error array #X [slope trimming value] (error a1 - error a2) equal to the difference in errors of error array #Y [slope trimming value] (error a1 - error a2).

[0055] (9) The temperature compensation information derivation unit 153 derives the identified slope trimming value as the final "slope trimming value" for setting the slope of the bandgap circuit 31, and writes the derived "slope trimming value" as temperature compensation information to the slope trimming value memory 4.

[0056] The fact that error array #X[slope trimming value] = error array #Y[slope trimming value] indicates that the reference potential output from the reference potential generation circuit 3 at the high-temperature setting X matches the reference potential output from the reference potential generation circuit 3 at the low-temperature setting Y. The purpose of slope trimming is to find the condition in which the "reference potential does not change" at the high-temperature setting X and the low-temperature setting Y, so the slope trimming value means that this condition has been met.

[0057] (10) From this point onward, the contents of the tilt trimming value memory 4 are fixed to the "tilt trimming value".

[0058] (11) The measurement condition setting unit 151 updates the gain trimming value memory 5 by writing the successively changed gain trimming value to the gain trimming value memory 5 from the data input terminal T2. The error calculation unit 152 calculates the error a1 at the "first input potential a1" and the error a2 at the "second input potential a2" each time the gain trimming value is updated, and identifies the gain trimming value at which the two match (the smallest possible match).

[0059] (12) The temperature compensation information derivation unit 153 derives the gain trimming value identified by the error calculation unit 152 as the final "gain trimming value" for setting the gain of the gain amplifier 33, and writes the derived "gain trimming value" as temperature compensation information to the gain trimming value memory 5.

[0060] The "slope trimming value" is set so that the reference potential output from the reference potential generation circuit 3 at the high temperature setting temperature X matches the reference potential output from the reference potential generation circuit 3 at the low temperature setting temperature Y. Under these conditions, the "gain trimming value" means that the reference potential is correct, with error a1 - error a2 = 0. By storing the "slope trimming value" in the slope trimming value memory 4 and the "gain trimming value" in the gain trimming value memory 5, the "reference potential can be set correctly" at both the high temperature setting temperature X and the low temperature setting temperature Y.

[0061] Assuming there are no other errors besides the reference potential, such as offset errors, it is clear that the reference potential is correct if both errors in the AD conversion results of the two input potentials are zero, as shown in Figure 12(a). If errors a1 and a2 are not equal, it is clear that the reference potential is incorrect.

[0062] If there are errors other than the reference potential, such as offset errors, then, as shown in Figure 12(b), there is a correlation between (error a1 - error a2) and the reference potential, and if error a1 - error a2 = 0, then the reference potential is correct. Similarly, if error a1 and error a2 are not equal, then the reference potential is incorrect.

[0063] If the reference potential is correct, with error a1 - error a2 = 0, then, as shown in Figure 12(c), the correct digital conversion value can be obtained by adding the reciprocal of the error to the digital value output from the AD converter 2.

[0064] From (13) onward, the contents of gain trimming value memory 5 are fixed to the "gain trimming value".

[0065] (14) The error calculation unit 152 temporarily stores the error a1 (or error a2) in the slope trimming value and gain trimming value as the error #Y under the condition of "appropriate reference potential". The error calculation unit 152 also temporarily stores the temperature digital value at the low temperature setting temperature Y as the temperature digital value #Y, and terminates the product inspection process at the low temperature setting temperature Y.

[0066] (Product inspection process at medium temperature setting Z: Figure 11) (15) The contents of the slope trimming value memory 4 are fixed to the "slope trimming value", and the contents of the gain trimming value memory 5 are fixed to the "gain trimming value".

[0067] (16) The error calculation unit 152 temporarily stores the error a1 (error a2 is also acceptable) in the 《Slope trimming value》 and 《Gain trimming value》 as the 《Error #Z》 under the condition of "appropriate reference potential". Also, the error calculation unit 152 temporarily stores it as the temperature digital value 《Temperature digital value #Z》 at the medium temperature set temperature Z.

[0068] (17) The temperature compensation information derivation unit 153 uses the 《Error #X》 and 《Temperature digital value #X》 temporarily stored in (3), the 《Error #Y》 and 《Temperature digital value #Y》 temporarily stored in (14), and the 《Error #Z》 and 《Temperature digital value #Z》 temporarily stored in (16) to calculate 《α XZ 》, 《β XZ 》, 《α ZY 》, 《β ZY 》 according to the following formulas. 《α XZ 》 = (《Error #X》 - 《Error #Z》) / (《Temperature digital value #X》 - 《Temperature digital value #Z》) 《β XZ 》 = 《Error #X》 - 《α XZ 》 * 《Temperature digital value #X》 《α ZY 》 = (《Error #Z》 - 《Error #Y》) / (《Temperature digital value #Z》 - 《Temperature digital value #Y》) 《β ZY 》 = 《Error #Y》 - 《α ZY 》 * 《Temperature digital value #Z》

[0069] (18) The temperature compensation information derivation unit 153 derives the calculated 《α XZ 》, 《β XZ 》, 《α ZY 》, 《β ZY 》, 《Temperature digital value #Z》 as the 《Temperature characteristic parameter value》, writes the derived 《Temperature characteristic parameter value》 into the temperature characteristic parameter value memory 7 as temperature compensation information, and ends the product inspection process.

[0070] 《α XZ 》 is the coefficient of the first linear approximation formula (see Figure 6) for calculating the approximation error above 《Temperature digital value #Z》, and 《β XZ》 is the constant term of the first linear approximation equation. 《α ZY 》 is the coefficient of the second linear approximation formula (see Figure 6) used to calculate the approximation error when the temperature digital value #Z is less than 《β ZY 》 is the constant term of the second linear approximation equation.

[0071] As described above, this embodiment is an AD converter 1 (analog-to-digital converter) that converts an analog input potential to a digital AD conversion result (analog-to-digital conversion result), comprising: a reference potential generation circuit 3 that generates a reference potential; an AD converter 2 (analog-to-digital converter) that converts the input potential to a digital value using the reference potential; a temperature correction calculator 8 that calculates a temperature correction value using a temperature error function that determines the error from the temperature; and an adder 10 that outputs a value obtained by adding the temperature correction value calculated by the temperature correction calculator 8 to the digital value converted by the AD converter 2 as the AD conversion result. This configuration allows for a comprehensive reduction in temperature dependence across the entire device, enabling the provision of a high-speed, high-precision AD converter 1 with low temperature dependence in a cost-effective manufacturing manner.

[0072] Furthermore, in this embodiment, the reference potential generation circuit 3 includes a bandgap circuit 31 incorporating a temperature compensation circuit that combines a positively dependent resistor having a positive dependence on temperature and a negatively dependent resistor having a negative dependence on temperature; a gain amplifier 33 configured to amplify or attenuate the output potential of the bandgap circuit 31 and whose gain can be changed; and a gain trimming unit 34 that sets the gain of the gain amplifier 33 using a gain trimming value for setting the gain of the gain amplifier 33 to a value that amplifies or attenuates the output potential of the bandgap circuit 31 to a reference potential. With this configuration, the reference potential output from the reference potential generation circuit 3 is set appropriately.

[0073] Furthermore, in this embodiment, the bandgap circuit 31 is configured to change the slope of its temperature output characteristics, and the reference potential generation circuit 3 includes a slope trimming unit 32 that sets the slope of the temperature output characteristics of the bandgap circuit 31 using a slope trimming value for setting the temperature output characteristics of the bandgap circuit 31 to a slope where the output potentials are equal under two temperature conditions. With this configuration, the slope of the temperature output characteristic of the bandgap circuit 31 is set appropriately.

[0074] Furthermore, in this embodiment, the temperature correction calculator 8 calculates a temperature correction value using two or more temperature error functions set for each temperature range. This configuration allows for easy derivation of an approximate formula for the temperature output characteristics.

[0075] Furthermore, in this embodiment, the temperature error function is a linear function. This configuration allows for the calculation of temperature correction values ​​with simple calculations.

[0076] Furthermore, in this embodiment, a temperature sensor 6 is provided that outputs a digital temperature value having a linear correlation with the measured temperature, and a temperature correction calculator 8 calculates a temperature correction value from the digital temperature value using a temperature error function. This configuration enables accurate temperature compensation using a digital temperature value that has a linear correlation with the actual temperature.

[0077] Furthermore, this embodiment includes a temperature output terminal T1 that outputs a digital temperature value. This configuration allows temperature digital values ​​to be provided to other AD converters 1a to 1c.

[0078] Furthermore, in this embodiment, a temperature input terminal T3 is provided to which a digital temperature value having a linear correlation with the measured temperature is input, and the temperature correction calculator 8 calculates a temperature correction value from the digital temperature value using a temperature error function. This configuration allows the temperature sensor 6 to be placed externally, enabling the use of a common temperature sensor 6 across multiple AD converters 1a to 1c.

[0079] Furthermore, in this embodiment, the method for deriving temperature compensation information for deriving the temperature characteristic parameter value of the temperature error function used in the AD conversion device 1 in the product inspection process is to derive the temperature characteristic parameter value using the errors of the AD conversion results of the input potentials under at least three temperature conditions, while the error values ​​of the AD conversion results for two input potentials are the same. This configuration allows for the easy derivation of a temperature error function that comprehensively reduces temperature dependence across the entire device.

[0080] Furthermore, in this embodiment, the temperature compensation information derivation method for deriving the gain trimming value used in the AD conversion device 1 in the product inspection process is characterized in that the gain trimming value is derived using the error of the AD conversion result with respect to the input potential when the error values ​​of the AD conversion results with respect to the two input potentials are equal. This configuration allows the reference potential generation circuit 3 to output an appropriate reference potential.

[0081] Furthermore, in this embodiment, the method for deriving temperature compensation information for deriving the slope trimming value used in the AD converter 1 during the product inspection process involves calculating the difference in errors of the AD conversion results for two input potentials while changing the slope of the temperature output characteristic under two temperature conditions, and deriving the slope of the temperature output characteristic at which the difference in errors is equal under the two temperature conditions as the slope trimming value. This configuration allows for error correction that encompasses both the AD converter 2 and the reference potential generation circuit 3 by setting the slope of the temperature output characteristic to match the error values ​​of the AD conversion results for the two input potentials. This results in higher correction accuracy compared to methods that correct the AD converter 2 and the reference potential generation circuit 3 individually (where deviations accumulate).

[0082] It is clear that the present invention is not limited to the above embodiments, and that each embodiment can be modified as appropriate within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-mentioned components are not limited to the above embodiments, and can be set to a number, position, shape, etc. that is suitable for carrying out the present invention. In each figure, the same reference numeral is used for the same component. [Explanation of Symbols]

[0083] 1. 1a~1d AD converter (analog-to-digital converter) 2 AD converters 3 Reference potential generation circuit 4. Tilt trimming value memory 5. Gain trimming value memory 6. Temperature sensor 7. Temperature characteristic parameter value memory 8 Temperature correction calculator 9. Temperature compensation value register 10 Adder 31 Bandgap Circuits 32. Tilt trimming section 33 Gain Amplifier 34 Gain trimming section 61 Forward Voltage Generation Circuit 62 AD converter for temperature sensors 100 Product Inspection Equipment 110 Input Potential Generation Circuit 120 Target conversion result storage unit 130 AD Conversion Result Reception Unit 140 Temperature digital value receiving section 150 Control Unit 151 Measurement condition setting unit 152 Error calculation section 153 Temperature compensation information derivation unit T1 Temperature output terminal T2 Data Input Terminal T3 Temperature input terminal Tin input terminal Tout output terminal

Claims

1. Converts an analog input potential into a digital analog-to-digital conversion result, A reference potential generation circuit that generates a reference potential, An analog-to-digital converter that converts the input potential into a digital value using the aforementioned reference potential, A temperature correction calculator that calculates a temperature correction value using a temperature error function that determines the error from the temperature, An adder that outputs a value obtained by adding the temperature correction value calculated by the temperature correction calculator to the digital value converted by the analog-to-digital converter as the analog-to-digital conversion result, A method for deriving temperature compensation information for deriving the temperature characteristic parameter value of the temperature error function used in an analog-to-digital conversion device equipped with the following, in a product inspection process, A method for deriving temperature compensation information, characterized in that the error values ​​of the analog-to-digital conversion results for two input potentials are the same, and the temperature characteristic parameter value is derived using the errors of the analog-to-digital conversion results for at least three temperature conditions.

2. Converts an analog input potential into a digital analog-to-digital conversion result, A reference potential generation circuit that generates a reference potential, An analog-to-digital converter that converts the input potential into a digital value using the aforementioned reference potential, A temperature correction calculator that calculates a temperature correction value using a temperature error function that determines the error from the temperature, An adder that outputs a value obtained by adding the temperature correction value calculated by the temperature correction calculator to the digital value converted by the analog-to-digital converter as the analog-to-digital conversion result, It is equipped with, The aforementioned reference potential generation circuit is A bandgap circuit incorporating a temperature compensation circuit that combines a positively dependent resistor that has a positive dependence on temperature and a negatively dependent resistor that has a negative dependence on temperature, A gain amplifier configured to amplify or attenuate the output potential of the bandgap circuit, with a changeable gain, A method for deriving temperature compensation information used in an analog-to-digital conversion device, comprising: a gain trimming unit that sets the gain of the gain amplifier using a gain trimming value for setting the gain of the gain amplifier to a value that amplifies or attenuates the output potential of the bandgap circuit to the reference potential; and a method for deriving the gain trimming value used in an analog-to-digital conversion device in a product inspection process, wherein the gain trimming value is derived in a product inspection process. A method for deriving temperature compensation information, characterized in that the error values ​​of the analog-to-digital conversion results for the input potentials are equal, and the gain trimming value is derived using the error of the analog-to-digital conversion result for the input potentials.

3. Converts an analog input potential into a digital analog-to-digital conversion result, A reference potential generation circuit that generates a reference potential, An analog-to-digital converter that converts the input potential into a digital value using the aforementioned reference potential, A temperature correction calculator that calculates a temperature correction value using a temperature error function that determines the error from the temperature, An adder that outputs a value obtained by adding the temperature correction value calculated by the temperature correction calculator to the digital value converted by the analog-to-digital converter as the analog-to-digital conversion result, It is equipped with, The aforementioned reference potential generation circuit is A bandgap circuit incorporating a temperature compensation circuit that combines a positively dependent resistor that has a positive dependence on temperature and a negatively dependent resistor that has a negative dependence on temperature, A gain amplifier configured to amplify or attenuate the output potential of the bandgap circuit, with a changeable gain, The system comprises a gain trimming unit that sets the gain of the gain amplifier using a gain trimming value for setting the gain of the gain amplifier to a value that amplifies or attenuates the output potential of the bandgap circuit to the reference potential, The bandgap circuit is configured to allow the slope of the temperature output characteristic to be changed. The aforementioned reference potential generation circuit is a temperature compensation information derivation method that derives a slope trimming value used in an analog-to-digital conversion device in a product inspection process, which is used to set the slope of the temperature output characteristics of the bandgap circuit using a slope trimming value for setting the slope of the temperature output characteristics of the bandgap circuit to a slope such that the output potentials are equal under two temperature conditions, A method for deriving temperature compensation information, characterized by calculating the difference in errors of the analog-to-digital conversion results for two input potentials while changing the slope of the temperature output characteristic under two temperature conditions, and deriving the slope of the temperature output characteristic at which the difference in errors is equal under the two temperature conditions as the slope trimming value.

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