WO2014207870A1 - アナログデジタル変換器 - Google Patents
アナログデジタル変換器 Download PDFInfo
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- WO2014207870A1 WO2014207870A1 PCT/JP2013/067698 JP2013067698W WO2014207870A1 WO 2014207870 A1 WO2014207870 A1 WO 2014207870A1 JP 2013067698 W JP2013067698 W JP 2013067698W WO 2014207870 A1 WO2014207870 A1 WO 2014207870A1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/10—Calibration or testing
- H03M1/1009—Calibration
- H03M1/1033—Calibration over the full range of the converter, e.g. for correcting differential non-linearity
- H03M1/1038—Calibration over the full range of the converter, e.g. for correcting differential non-linearity by storing corrected or correction values in one or more digital look-up tables
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/002—Provisions or arrangements for saving power, e.g. by allowing a sleep mode, using lower supply voltage for downstream stages, using multiple clock domains or by selectively turning on stages when needed
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/06—Continuously compensating for, or preventing, undesired influence of physical parameters
- H03M1/0602—Continuously compensating for, or preventing, undesired influence of physical parameters of deviations from the desired transfer characteristic
- H03M1/0609—Continuously compensating for, or preventing, undesired influence of physical parameters of deviations from the desired transfer characteristic at two points of the transfer characteristic, i.e. by adjusting two reference values, e.g. offset and gain error
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/06—Continuously compensating for, or preventing, undesired influence of physical parameters
- H03M1/0602—Continuously compensating for, or preventing, undesired influence of physical parameters of deviations from the desired transfer characteristic
- H03M1/0612—Continuously compensating for, or preventing, undesired influence of physical parameters of deviations from the desired transfer characteristic over the full range of the converter, e.g. for correcting differential non-linearity
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
Definitions
- the present invention relates to an analog-digital converter, for example, an analog-digital converter whose accuracy can be improved by digital correction.
- Non-Patent Document 1 a reference analog-to-digital converter that is slower and more accurate than the correction-target analog-to-digital converter is input to the correction-target analog-to-digital converter. Connected in parallel, correction is performed using the digital output of the reference analog-to-digital converter as a reference signal.
- Non-Patent Document 2 discloses an analog-digital converter that can perform digital correction without using a reference signal that requires such accuracy.
- the digital correction type analog-digital converter includes an analog-to-digital conversion unit that converts an analog signal into a digital signal and a digital correction unit that receives the digital output of the analog-to-digital conversion unit and digitally corrects the digital output.
- the digital correction type analog-digital converter can maintain high conversion accuracy by compensating for the lack of performance of the analog circuit unit by digital correction. Since a low-performance analog circuit is sufficient, there is an advantage that power consumption and circuit area can be significantly reduced.
- the linearity of the analog-digital conversion characteristics of the analog-to-digital converter is reduced due to the lack of open-loop gain and nonlinearity of the operational amplifier, resulting in conversion accuracy. Deteriorates. Low-performance operational amplifiers can be adopted by digitally correcting the above effects.
- the capacitance value variation of the capacitance element also reduces the linearity of the conversion characteristics, since the capacitance value variation can be allowed by digital correction, a capacitance element having a small capacitance value can be employed. As a result, the power consumption and circuit area of the analog-digital converter can be significantly reduced.
- the capacitance value variation of the capacitance element reduces the linearity of the conversion characteristic.
- the capacitance value variation can be allowed by digital correction, a capacitance device having a small capacitance value can be adopted. As a result, the power consumption and circuit area of the analog-digital converter can be significantly reduced.
- Non-Patent Document 1 when digital correction type analog-digital converter disclosed in Non-Patent Document 1 is used, the conversion accuracy of the corrected analog-digital converter is limited by the conversion accuracy of the reference analog-digital converter. For this reason, it is considered difficult to obtain conversion accuracy of, for example, about 13 bits or more by correction using these reference signals.
- FIG. 1 is a schematic diagram showing an example of the configuration of an analog-digital converter studied as a premise of the present invention.
- ADC analog-digital converter
- This DC voltage shift application mechanism can be equivalently realized by adding a capacitive element or a switch to the internal circuit of the analog-digital converter (ADC), for example.
- the odd sample side digital correction unit and the even sample side digital correction unit are correction coefficients for the digital output corresponding to the odd numbered sample and the digital output corresponding to the even number sample of the analog-to-digital conversion unit (ADC), respectively.
- Perform digital correction using The searched correction coefficient is searched by searching for the correction coefficient so that the difference between the corrected output of the even sample side digital correction unit and the corrected output of the odd sample side digital correction unit is “2 ⁇ ” expected from the input.
- the above digital correction can be carried out using. In this method, as long as the DC voltage shift value is always constant, there is no problem even if the value itself deviates from the design value.
- the analog-digital converter includes an attenuation circuit, a first selection circuit, an analog-digital conversion unit, and a correction unit.
- the attenuation circuit sequentially receives a plurality of first analog voltages having different voltage values, and sequentially outputs a plurality of second analog voltages by attenuating the plurality of first analog voltages with a predetermined attenuation rate.
- the first selection circuit sequentially inputs a plurality of sets of first and second analog voltages, each of which includes a first analog voltage and a second analog voltage obtained by attenuating the first analog voltage. Each analog voltage is selected and output at different timings.
- the analog-to-digital converter converts the plurality of sets of first and second analog voltages output from the first selection circuit into a plurality of sets of first and second digital signals, respectively.
- the correction unit multiplies M bits (M is an integer of 1 or more) of the plurality of sets of first and second digital signals based on the plurality of sets of first and second digital signals, respectively. Search for a correction factor.
- the schematic which shows the structural example In the analog-digital converter examined as a premise of this invention, it is the schematic which shows the structural example. It is the schematic which shows the example of a structure in the analog-digital converter by Embodiment 1 of this invention. It is a wave form diagram which shows an example of the analog signal input into the analog digital conversion part of FIG. 2A. It is the schematic which shows the structural example in the analog-digital converter by Embodiment 2 of this invention. It is a timing chart which shows the operation example of the principal part in FIG. 3A. It is the schematic which shows the structural example in the analog-digital converter by Embodiment 3 of this invention. It is a timing chart which shows the operation example of the principal part in FIG. 4A.
- the constituent elements are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.
- the shapes, positional relationships, etc. of the components, etc. when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.
- FIG. 2A is a schematic diagram illustrating a configuration example of the analog-digital converter according to Embodiment 1 of the present invention.
- FIG. 2B is a waveform diagram illustrating an example of an analog signal input to the analog-to-digital converter in FIG. 2A.
- the attenuation signal 21 is connected to the correction signal application terminal, and the two input nodes of the path switching multiplexer (first selection circuit) 22 are the correction signal application terminal and the output node of the attenuation circuit 21, respectively. Is connected.
- the output of the path switching multiplexer 22 is input to an analog / digital converter (ADC) 23.
- ADC analog / digital converter
- the attenuation circuit 21 is configured by a resistance voltage dividing circuit.
- the multiplier 27 outputs the multiplication result of the odd-sample-side corrected analog-digital conversion result and the attenuation factor estimated value (attenuation coefficient) a EST supplied from the correction coefficient search unit 26.
- the subtraction unit (error detection unit) 28 outputs a result obtained by subtracting the multiplication result from the even-sample-side corrected analog-digital conversion result.
- the subtraction result is input to the correction coefficient search unit 26 as “error e”.
- the odd sample side digital correction unit 24, the even sample side digital correction unit 25, the correction coefficient search unit 26, the multiplication unit 27, and the subtraction unit 28 constitute a correction unit 20a.
- the correction unit 20a is not particularly limited, but can be realized by a digital arithmetic circuit such as an FPGA or a processor.
- an input path switch (input switch) 29 is connected to the input node of the analog-digital conversion unit 23 in parallel with the path switching multiplexer 22.
- the input path switch 29 inputs the original input signal voltage (analog input voltage) VIN to the analog-to-digital converter 23 when controlled to be on.
- the control unit 30 controls on / off of the input path switch 29 and selection of the path switching multiplexer 22.
- the correction signal is a plurality of (in this example, three) analog voltages (first analog voltage) V 1 to V 1 that change in a stepwise manner as shown in the “correction signal waveform” shown in FIG. 2B. have V 3, the value of each analog voltage is accurately held by two turns period of the analog-to-digital conversion cycle.
- ADC input waveform shown in FIG.
- the analog-to-digital converter 23 directly receives the correction signal voltages (V 1 to V 3 ) at odd-numbered analog-digital conversion periods, and at even-numbered values, A voltage (second analog voltage) (aV 1 to aV 3 ) obtained by attenuating the correction signal by a times is input via the attenuation circuit 21.
- the control unit 30 selects the path switching multiplexer 22 so as to have such an “ADC input waveform”. Specifically, for each cycle of the correction signal, the control unit 30 selects the correction signal during a part (here, half) of each cycle, and outputs from the attenuation circuit 21 during the remaining period. A signal (second analog signal) is selected.
- the correction coefficient search unit 26 forms a pair of values obtained by multiplying the odd sample-side corrected analog-digital conversion result by the attenuation rate estimated value a EST.
- the correction coefficient W i and the attenuation rate estimation value a EST are searched by the following adaptive control algorithm so as to be equal to the even-sample-side corrected analog-digital conversion result.
- the multiplier 27 multiplies D OUT ODD and a EST to obtain a multiplication result.
- the subtraction unit (error detection unit) 28 calculates the difference between D OUT EVEN and the multiplication result as an error e as shown in Expression (3).
- the correction coefficient search unit 26 based on the error e, the digital outputs D i ODD , D i EVEN , and D OUT ODD of the analog-digital conversion unit 23, the correction coefficient W i and the attenuation rate estimated value.
- a Search for an EST As an example, when performing a search in LMS (Least Mean Square) algorithm, for example, a W i in Equation (4), can be searched for a EST in equation (5). “a” is a design value of the attenuation rate of the attenuation circuit 21.
- ⁇ Wi and ⁇ a are step sizes of the LMS algorithm, and may be set to appropriate values in consideration of a trade-off between search speed and search accuracy.
- the search (constant multiple of W i with respect to the solution of example W i can become a solution) ambiguity results to eliminate the correction coefficient W 1 of the MSB above operation while fixing to 1/2 I do.
- the corrected correction coefficient value W i is uniformly 1/2 / W 1 times the true value (W 1 is the true value of the MSB correction coefficient), and as a result, 1/2 / W A conversion gain error of 1 is generated.
- the relative ratio between each Wi value is equal to the ratio between true values, the linearity of the analog-to-digital conversion is fully compensated.
- a EST converges to a.
- the analog-digital conversion unit 23 has a serial connection configuration of MDAC (Multiplying DAC) circuits.
- MDAC Multiplying DAC
- the linearity of the analog-digital conversion can be further improved by correcting the third-order distortion and the fifth-order distortion of the operational amplifier used in the first-stage MDAC circuit.
- a correction coefficient W i be more supply, based on the third-order distortion correction coefficient B 3, the odd samples side corrected analog-to-digital conversion result D OUT oDD calculated as equation (6).
- the even sample-side digital correction unit 25 and the even-numbered digital output D i EVEN (i 1, 2,..., M) of the analog-digital conversion unit 23 and the same correction supplied from the correction coefficient search unit 26.
- the even-sample-side corrected analog-digital conversion result D OUT EVEN is calculated as in equation (7).
- the correction coefficient search unit 26 calculates the equation (2) based on the error e, the digital outputs D i ODD and D i EVEN of the analog-digital conversion unit 23, and D OUT ODD.
- the correction coefficient W i is searched for in 4
- the attenuation factor estimated value a EST is searched for in Expression (5)
- the third-order distortion correction coefficient B 3 is searched for in Expression (8).
- ⁇ B3 may be set to an appropriate value in consideration of a trade-off between search speed and search accuracy.
- the correction coefficient search unit 26 can also search for a correction coefficient by removing the influence of the DC offset voltage of the analog-digital conversion unit 23.
- a value obtained by subtracting the DC correction coefficient ⁇ V DC from the error e (Equation (9)) is set as the error e ′, and Equations (10) and (5) are replaced by e ′.
- the correction coefficient W i and the attenuation factor estimated value a EST are searched.
- the direct current correction coefficient ⁇ V DC is searched by the equation (12).
- the attenuation rate estimated value a EST is by converging the a REAL, absorbs the impact of the attenuation factor variations, it can maintain a precise search of the correction coefficient W i.
- This linearity is an attenuation circuit using a passive element typified by a resistance voltage dividing circuit. 21 is fully guaranteed.
- the method of this embodiment does not particularly use an element that requires accuracy, and highly accurately corrects the non-linearity of analog-digital conversion that can occur in pipelines, cyclic, successive approximation analog-digital converters, etc. can do.
- it is possible to improve the conversion accuracy in the analog-digital converter.
- it is not necessary to change the internal circuit of the analog-digital converter 23. Therefore, for example, it is possible to perform highly accurate digital correction for a commercially available analog-digital converter completed as a part.
- the power consumption and circuit area of the analog-digital converter can be significantly reduced.
- low-performance operational amplifiers can be used because the effects of the lack of open-loop gain and nonlinearities of the operational amplifiers are digitally corrected with high accuracy. Can be adopted. Furthermore, since the capacitance value variation of the capacitive element and the influence of the DC offset voltage are digitally corrected with high accuracy, a capacitive element having a small capacitance value and a MOS transistor having a small gate width can be employed.
- the influence of the capacitance value variation of the capacitive element and the DC offset voltage is digitally corrected with high accuracy, so that a capacitive element having a small capacitance value and a MOS transistor having a small gate width are also used. Can be adopted. As a result, the power consumption and circuit area of the analog-digital converter can be significantly reduced.
- V 1 , V 2 , and V 3 voltage variations of the correction signal.
- voltage variations larger than the number of coefficients to be searched are necessary as a minimum.
- a resistance voltage dividing circuit composed of a plurality of resistance elements is used as the attenuating circuit 21, but instead, for example, a capacitance voltage dividing circuit in which a plurality of capacitance elements are connected in series can be used. .
- V 1 , V 2 , and V 3 in FIG. 2B can be arbitrarily determined as long as they are different in principle. What is necessary as the voltage condition is that the input voltage ratio of the odd-numbered sample and the even-numbered sample to the analog-to-digital converter 23 is always kept at a constant value a by taking FIG. 2B as an example. This condition ensures that the value of “a” is unchanged, so that the voltage (V 1 , V 1 , V 2 , V 3 ) can be satisfied by keeping them constant.
- V1 ′ ⁇ ⁇ , V2 ′ ⁇ ⁇ , V3 ′ ⁇ ⁇ ,... are input as correction signals.
- the values of V1 ′, V2 ′, V3 ′,... Can be arbitrarily determined as long as they are different values as in the method of the present embodiment, but the voltage value of ⁇ is It must be immutable.
- an analog adder circuit using an operational amplifier may be used, but in this case, distortion characteristics of the operational amplifier, etc.
- an error may occur between the voltage value 2 ⁇ at V1 ′ and the voltage value 2 ⁇ at V2 ′.
- an attenuation factor for example, a resistance voltage dividing ratio
- a EST is multiplied at the output of the odd sample side digital correction unit 24.
- a EST may be multiplied at the output of the even sample side digital correction unit 25.
- the search value of a EST rather than attenuation factor a of the attenuation circuit 21, becomes to the reciprocal 1 / a, it can be searched similarly to desired correction coefficients W i.
- a search may be performed using the following equations (13) to (15).
- the above description is a case where the analog-digital converter operates in the correction operation mode, for example.
- the control unit 30 in FIG. 2A selects the path switching multiplexer (first selection circuit) 22 in a state where the input path switch (input switch) 29 is controlled to be off, and corrects the correction unit 20a.
- the coefficient Wi is searched.
- the analog-digital converter according to the present embodiment has a normal operation mode in addition to such a correction operation mode.
- the control unit 30 controls the input path switch 29 to be on, and controls each switch in the path switching multiplexer 22 to be off (that is, the output of the path switching multiplexer 22 is in an open state).
- VIN analog input signal voltage
- the correction unit 20a uses the digital output D i and the correction coefficient value W i obtained by searching in the correction operation mode, the correction unit 20a performs the calculation of Expression (16) in the even sample side digital correction unit 25.
- the even-sample-side digital correction unit 25 performs the calculation of Expression (16) for all the samples regardless of whether they are odd-numbered samples or even-numbered samples, and the output (corrected digital output signal) D OUT is It becomes the output of the digital correction type analog-digital converter as a whole during normal operation.
- FIG. 9 is a diagram illustrating an example of a simulation result for the analog-digital converter in FIG. 2A and an example of a simulation result for the analog-digital conversion unit alone in FIG. 2A as a comparative example.
- the output spectrum is observed by using the input signal voltage VIN .
- digital correction is not performed (when the analog-digital conversion unit 23 is used alone), the linearity accuracy is 6.6 bits, but digital correction is performed using the method of the present embodiment.
- the linearity accuracy is improved to 12.0 bits.
- the above is merely an example, and the correction method of this embodiment is effective for analog-digital converters with various resolutions.
- the analog-to-digital converter according to the first embodiment performs analog-to-digital conversion on a certain voltage and a voltage obtained by attenuating the voltage with a fixed attenuation rate, and based on the conversion result and the adaptive control algorithm, The correction coefficient of the analog-digital conversion unit is searched, and the digital output of the analog-digital conversion unit is corrected using the searched correction coefficient.
- conversion accuracy of, for example, about 13 bits or more can be realized without using a high-accuracy reference signal and without changing the circuit of the analog-to-digital converter. .
- analog-digital converter according to the first embodiment is particularly useful when the on-board correction for generating the “ADC input waveform” in FIG. 2B is used externally, but is not limited thereto, and the “ADC input waveform” is not limited thereto. Even when using on-chip correction to generate in an analog-to-digital converter, a beneficial effect is obtained.
- V 1 ⁇ V 3 in the odd-numbered samples the example of inputting the aV 1 ⁇ aV 3 in even-numbered samples
- the order of the input may be changed as appropriate .
- V 1 to V 3 may be input for even-numbered samples, and aV 1 to aV 3 may be input for odd-numbered samples.
- V 1 to V 3 are sequentially input for consecutive samples, and then continuous AV 1 to aV 3 may be sequentially input with the samples to be processed.
- the correction unit 20 a includes a memory or the like that temporarily holds the digital signal from the analog-digital conversion unit 23, the digital signals for V 1 to V 3 and aV 1 to aV 3 are converted to the analog-digital conversion unit 23.
- V 1 and aV 1 can be searched for as a set regardless of the order of input.
- the value of V 1 needs to be unchanged when V 1 is input to the analog-digital converter 23 and when aV 1 is input.
- a method of searching for the attenuation rate estimated value (attenuation coefficient) a EST is used, but a fixed value may be used depending on the case. Specifically, if the variation in the attenuation rate a of the attenuation circuit 21 can be controlled with high accuracy, a EST can be set to a fixed value. In this case, since the coefficient to be searched is reduced, for example, the search speed can be increased. However, in practice, it is not easy to control the variation of the passive elements (resistor or capacitor) constituting the damping circuit 21, in particular, because that can be a more difficult when performing on-board correction, the a EST It is preferable to use a search method.
- FIG. 3A is a schematic diagram showing a configuration example of the analog-digital converter according to Embodiment 2 of the present invention.
- FIG. 3B is a timing chart showing an operation example of the main part in FIG. 3A.
- the analog-digital converter of FIG. 3A shows details of a method for generating the correction signal. Since there is no particular difference between FIG. 2A and FIG. 3A regarding the configuration and operation of the analog-digital conversion unit 23 and the subsequent correction unit 20a, detailed description thereof will be omitted.
- N outputs at N resistance voltage dividing nodes of the resistance ladder type multi-voltage generation unit (correction resistance voltage dividing circuit) 31 are input to the selector (second selection circuit) 32, and the output of the selector 32 is output.
- the node becomes the correction signal application terminal described in the first embodiment. That is, the output node of the selector 32 is connected to the attenuation circuit 21, and the output node of the selector 32 and the output node of the attenuation circuit 21 are connected to two input nodes of the path switching multiplexer 22, respectively.
- the output of the path switching multiplexer 22 is input to the analog / digital converter 23.
- the attenuation circuit 21 is formed of a resistance element having resistance values of R 1 and R 2 and is a resistance voltage dividing circuit that realizes an attenuation rate of R 2 / (R 1 + R 2 ).
- the selection signal of the selector 32 and the path switching signal of the path switching multiplexer 22 are generated by the selection signal generator 33.
- the original input signal voltage VIN to the analog / digital conversion unit 23 is input to the analog / digital conversion unit 23 via the input path switch 29.
- the resistance ladder type multi-voltage generation unit 31 has a structure in which (N + 1) series-connected resistance elements are inserted between the power supply voltage and the ground. Depending on the resistance value of each resistance element, as shown in FIG. 3A, N different voltages V 1 to V N are generated at N resistance voltage dividing nodes.
- the selector 32 selects one of them according to the selection signals ⁇ 1 to ⁇ N from the selection signal generator 33. As a result, the stepwise correction signal waveform shown in FIG. 2B is generated at the output node of the selector 32.
- the resistance ladder type multi-voltage generation unit 31 and the selector 32 constitute a correction signal generation unit 34a.
- the resistance values of the resistance elements in the resistance ladder type multi-voltage generation unit 31 are made the same, and the selection signals ⁇ 1 to ⁇ N are sequentially activated. And make it go around. Therefore, as shown in the timing chart of FIG. 3B, the selection signals ⁇ 1 to ⁇ N sequentially and repeatedly become a high voltage, and the corresponding switch in the selector 32 is controlled to be turned on.
- the selection signal to the period of high voltage and 2 conversion cycles of the conversion clock (sampling clock) phi S of the analog-to-digital converter 23, as in the first embodiment, every two weeks period the voltage value Can generate a correction signal waveform in which is accurately maintained.
- the path switching signal ⁇ MUX of the path switching multiplexer 22 can be generated by the selection signal generation unit 33 by dividing the conversion clock ⁇ S of the analog / digital conversion unit 23 by two.
- the analog-digital converter operates in the normal operation mode after passing through such a correction operation mode.
- the input path switch 29 is turned on, and the switches in the selector 32 and the switches in the path switching multiplexer 22 are turned off. That is, the output node of the path switching multiplexer 22 is opened.
- the original input signal voltage VIN becomes the input voltage V ADC to the analog-to-digital converter 23.
- the correction signal generation unit 34a including the resistance ladder type multi-voltage generation unit 31 and the selector 32 is provided.
- the correction signal can be easily generated.
- FIG. 4A is a schematic diagram showing a configuration example of the analog-digital converter according to Embodiment 3 of the present invention.
- FIG. 4B is a timing chart showing an operation example of the main part in FIG. 4A.
- the analog-digital converter of FIG. 4A shows details of a method for generating the correction signal. Since there is no particular difference between FIG. 2A and FIG. 4A regarding the configuration and operation of the analog-digital conversion unit 23 and the subsequent correction unit 20a, detailed description thereof will be omitted.
- the correction digital signal D CAL is input to the digital / analog conversion unit (DAC) 41, and the output voltage V DAC of the digital / analog conversion unit 41 is applied as a correction signal via the DAC path switch 42.
- the rightmost node of the DAC path switch 42 is a correction signal application terminal in the first embodiment. That is, the rightmost node of the DAC path switch 42 is connected to the attenuation circuit 21, and the rightmost node of the DAC path switch 42 and the output node of the attenuation circuit 21 are connected to two input nodes of the path switching multiplexer 22, respectively. Is done.
- the output of the path switching multiplexer 22 is input to the analog / digital converter 23.
- the digital-analog converter 41 and the DAC path switch 42 constitute a correction signal generator 34b.
- the attenuation circuit 21 is formed of a resistance element having resistance values of R 1 and R 2 and is a resistance voltage dividing circuit that realizes an attenuation rate of R 2 / (R 1 + R 2 ).
- the conversion clock (sampling clock) ⁇ DAC of the digital / analog conversion unit 41 and the path switching signal ⁇ MUX of the path switching multiplexer 22 are converted from the conversion clock (sampling clock) ⁇ S of the analog / digital conversion unit 23 by the frequency divider 43. It can be generated by dividing by two.
- the path switching signal ⁇ MUX when the path switching signal ⁇ MUX is at a high voltage, the upper switch of the path switching multiplexer 22 is turned on, and the output voltages V 1 to V N of the digital / analog conversion unit 41 are analog. It is applied as an input voltage V ADC to the digital converter 23.
- the path switching signal ⁇ MUX when the path switching signal ⁇ MUX is a low voltage, the lower switch of the path switching multiplexer 22 is turned on, and the output voltages aV 1 to aV N of the attenuation circuit 21 are input voltages V to the analog / digital converter 23. Applied as ADC .
- the DAC path switch 42 is controlled to be turned on by the DAC path conduction signal ⁇ DACO .
- the analog-digital converter according to the third embodiment in addition to the various effects described in the first embodiment, it is possible to easily generate a correction signal by using the digital-analog converter 41. It becomes possible. At this time, the output voltage of the digital-analog converter 41 is not particularly a problem even if somewhat deviated from the design value during the conversion period of each output voltage phi DAC, need only be maintained constant. Therefore, it is possible to apply a low-accuracy digital-analog converter. Further, for example, when the present embodiment is applied to a system including a microcomputer or the like, by using a digital / analog conversion unit mounted in the microcomputer, the components associated with the correction signal generation unit 34b can be reduced. Addition is not particularly necessary.
- FIG. 5A is a schematic diagram showing a configuration example of an analog-digital converter according to Embodiment 4 of the present invention.
- FIG. 5B is a timing chart showing an operation example of the main part in FIG. 5A.
- the analog-digital converter of FIG. 5A shows details of a method for generating the correction signal. Since there is no particular difference between FIG. 2A and FIG. 5A regarding the configuration and operation of the analog-digital conversion unit 23 and the subsequent correction unit 20a, detailed description thereof will be omitted.
- a correction analog signal V CAL such as a sine wave is applied to the sample and hold circuit (S / H) 51, and the output voltage V SH of the sample and hold circuit 51 is for the S / H path.
- the correction signal is applied through the switch 52.
- the rightmost node of the S / H path switch 52 is the correction signal application terminal described in the first embodiment. That is, the right end node of the S / H path switch 52 is connected to the attenuation circuit 21, and the right end node of the S / H path switch 52 and the output node of the attenuation circuit 21 are two inputs of the path switching multiplexer 22, respectively. Connected to the node. The output of the path switching multiplexer 22 is input to the analog / digital converter 23.
- the sample and hold circuit 51 and the S / H path switch 52 constitute a correction signal generation unit 34c.
- the attenuation circuit 21 is formed of a resistance element having resistance values of R 1 and R 2 and is a resistance voltage dividing circuit that realizes an attenuation rate of R 2 / (R 1 + R 2 ).
- the operation clock ⁇ SH of the sample and hold circuit 51 and the path switching signal ⁇ MUX of the path switching multiplexer 22 can be generated by dividing the conversion clock ⁇ S of the analog / digital conversion unit 23 by two by the frequency divider 43. .
- the sample-and-hold circuit 51 has a property of holding the output voltage during one conversion period (strictly, a period obtained by excluding the sampling period from one conversion period).
- the path switching signal ⁇ MUX when the path switching signal ⁇ MUX is at a high voltage, the upper switch of the path switching multiplexer 22 is turned on, and the output voltages V 1 to V N of the sample and hold circuit 51 are analog. It is applied as an input voltage V ADC to the digital converter 23.
- the path switching signal ⁇ MUX when the path switching signal ⁇ MUX is a low voltage, the lower switch of the path switching multiplexer 22 is turned on, and the output voltages aV 1 to aV N of the attenuation circuit 21 are input voltages V to the analog / digital converter 23. Applied as ADC .
- the S / H path switch 52 is controlled to be turned on by the S / H path conduction signal ⁇ SHO .
- the correction signal can be easily generated by using the sample and hold circuit 51. It becomes possible. At this time, the output voltage of the sample-and-hold circuit 51 is not particularly a problem even if somewhat deviated from the design value during the conversion period of each output voltage phi SH, need only be maintained constant. Therefore, it is possible to apply a low precision sample and hold circuit.
- FIG. 6 is a schematic diagram illustrating a configuration example of a correction signal generation unit included in the analog-digital converter according to the fifth embodiment of the present invention.
- the correction signal generation unit 34d illustrated in FIG. 6 has a resistance ladder type configuration, and is a modification of the correction signal generation unit 34a illustrated in FIG. 3A of the second embodiment.
- N outputs from the N resistance voltage dividing nodes included in the first-stage resistor ladder 61 are respectively input to the selector [1] 62, and the output voltage V OUT1 is the upper end of the next-stage resistor ladder 63. Input as voltage.
- the M outputs from the M resistance voltage dividing nodes included in the next-stage resistor ladder 63 are respectively input to the selector [2] 64, and the output voltage V OUT2 is the correction signal described in the first embodiment. Voltage.
- the first-stage resistor ladder 61 has a structure in which (N + 1) resistor elements connected in series are inserted between the power supply voltage and the ground. According to the resistance value of each resistance element, N kinds of voltages are generated at N resistance voltage dividing nodes as shown in FIG. One of them is selected by the selector [1] 62 by the selection signals ⁇ 11 to ⁇ 1N , so that the output voltage V OUT1 is obtained.
- the next-stage resistor ladder 63 has a structure in which (M + 1) resistor elements connected in series are inserted between VOUT1 and the ground. With this structure, M voltages are further generated based on the output voltage VOUT1 selected by the selector [1] 62, one of which is selected by the selectors [2] 64 using the selection signals ⁇ 21 to ⁇ 2M. Is done.
- the output voltage V OUT2 of the selector [2] 64 can take (N ⁇ M) values. Therefore, there is an advantage that the number of resistance elements necessary to realize the number of voltage variations required for the correction signal can be reduced as compared with the second embodiment.
- the selection signals ⁇ 11 to ⁇ 1N and ⁇ 21 to ⁇ 2M are stepped like the other embodiments in which the output voltage V OUT2 serving as a correction signal is held for every two analog-digital conversion cycles. It is only necessary to appropriately control the voltage so that Although the lower end of the next-stage resistor ladder 63 is grounded here, it may be configured to be selectively connected to N resistance voltage dividing nodes of the first-stage resistor ladder 61. That is, a selector similar to the selector [1] 62 is separately provided, and the next-stage resistor ladder 63 further divides the voltage between adjacent resistor voltage-dividing nodes of the first-stage resistor ladder 61.
- FIG. 7 is a schematic diagram illustrating a configuration example around a correction signal generation unit included in the analog-digital converter according to the sixth embodiment of the present invention.
- the correction signal generation unit 34e illustrated in FIG. 7 has a resistance ladder type configuration, and is a modification of the correction signal generation unit 34a illustrated in FIG. 3A of the second embodiment.
- the analog-digital conversion unit 23 has a differential circuit configuration as an example.
- a selector [P] (third selection circuit) 71P connected to the power supply voltage V DD and a parallel resistor [P] 72P connected to each output thereof generate a positive-phase correction signal.
- the selector [N] (third selection circuit) 71N connected to the ground and the parallel resistor [N] 72N connected to the output generate a negative-phase correction signal.
- the difference between the voltage of the correction signal on the positive phase side and the voltage of the correction signal on the negative phase side is the voltage of the correction signal in the first embodiment.
- the correction signal on the positive phase side is input to the resistance voltage dividing type attenuation circuit including the resistance [A] 73A and the resistance [B] 73B for the attenuation circuit, and the input node on the upper side of the positive phase side of the path switching multiplexer 74, respectively. Is done.
- the correction signal on the negative phase side is input to the lower side of the negative phase side of the path switching multiplexer 74 and the resistance voltage dividing type attenuation circuit including the resistance [C] 73C and the resistance [D] 73D for the attenuation circuit. Input to each node.
- a voltage half of the power supply voltage that is, V DD / 2 is applied to the other ends of the positive phase side attenuation circuit and the negative phase side attenuation circuit.
- the voltage (average voltage) can be kept at V DD / 2.
- the output node of the positive phase side attenuation circuit is connected to the lower input node of the positive phase side of the path switching multiplexer 74.
- the output of the attenuation circuit on the negative phase side is connected to the upper input node on the negative phase side of the path switching multiplexer 74.
- the output node on the positive phase side of the path switching multiplexer 74 is connected to the upper input node on the positive phase side and the upper input node on the negative phase side of the inverting multiplexer 75.
- the output node on the opposite phase side of the path switching multiplexer 74 is connected to the lower input node on the opposite phase side of the inverting multiplexer 75 and the lower input node on the positive phase side.
- the voltage difference between the output voltage V ADC_N the output voltage V ADC_P opposite phase side of the positive phase side of the inverting multiplexer 75 becomes the differential input voltage V ADC to the analog digital converter 23.
- the case of a differential circuit configuration is taken as an example, but of course, the present invention can be similarly applied to a case of a single circuit configuration.
- the inverting multiplexer 75 may be omitted, only the above-described positive-phase side circuits may be provided, and the other end of the positive-phase side attenuation circuit may be grounded.
- each of the parallel resistor [P] 72P and the parallel resistor [N] 72N includes six resistors (R 3 to R 8 ) composed of the same combination of resistance values, and R 4 , R 5 , R 6 , R 7 , R 8 are assumed to be, for example, 2 times, 4 times, 8 times, 16 times, and 32 times, respectively, based on the resistance value of R 3 .
- Conversion clock phi S of the analog-to-digital converter 23 (not shown) is input to the frequency divider 76, a selector [P]
- Each of six selective switches 71P and the selector [N] in 71N are of the divider 76
- ON / OFF is controlled by each of the frequency- divided outputs ⁇ DIV of division by 4, division by 8, division by 16, division by 32, division by 64, and division by 128.
- the parallel resistance value on the positive phase side and the parallel resistance value on the negative phase side are controlled to be the same value R EFF .
- the correction differential signal voltage is “V DD ⁇ 2R / (R EFF + 2R)”.
- R EFF is 1 times the resistance of R 3, 2-fold, 3-fold, ..., sequentially varies so as such 64 times.
- the inverting multiplexer 75 with the voltage of the positive / negative correction signal, it is provided in order to further enhance the search capability of the correction coefficient W i. That is, with respect to the input range of the differential signal of the analog-to-digital converter 23, to allow the search for the correction factor W i after having covered the whole rather than half.
- the inversion control signal ⁇ SWAP of the inverting multiplexer 75 is at a high voltage, the inverting multiplexer 75 selects the upper node on the positive phase side and the lower node on the negative phase side, and the voltage of the correction differential signal is Since it is output as it is, the final voltage of the correction signal is a positive voltage.
- Path switching signal phi MUX path switching multiplexer 74 can be generated by divided by 2 conversion clock phi S of the analog-to-digital converter 23.
- the number of resistance elements required to realize the number of voltage variations required for the correction signal is the same as in the case of the second embodiment, as in the case of the fifth embodiment. The effect which can be reduced in comparison is obtained.
- FIG. 8 is a schematic diagram showing a configuration example of a part of the analog-digital converter according to the seventh embodiment of the present invention.
- the eighth embodiment for example, an example in which the digital correction method according to the present embodiment is applied to a pipeline analog-digital converter that is a commercially available chip component will be described.
- the configuration before the analog-digital conversion unit 81 is the same as the configuration of the other embodiments.
- the analog-digital converter in the eighth embodiment includes a pipeline analog-digital conversion unit 81.
- the pipeline analog-digital conversion unit 81 usually includes an analog-digital conversion unit 811 and a digital output generation unit (DEC) 812 connected to the output thereof.
- the digital output b i of the pipeline analog-digital conversion unit 81 is input to a digital output generation inverse processing unit (RDEC) 82, and the output is input to an odd sample side digital correction unit 83 and an even sample side digital correction unit 84.
- RDEC digital output generation inverse processing unit
- the odd sample side digital correction unit 83 outputs an odd sample side corrected analog-digital conversion result based on the odd number digital output of the digital output generation inverse processing unit 82 and the correction coefficient supplied from the correction coefficient search unit 85.
- the even sample side digital correction unit 84 outputs the even sample side corrected analog-digital conversion result based on the even number digital output of the digital output generation inverse processing unit 82 and the correction coefficient supplied from the correction coefficient search unit 85. .
- the multiplier 86 outputs the multiplication result of the odd-sample-side corrected analog-digital conversion result and the attenuation factor estimated value a EST supplied from the correction coefficient search unit 85.
- the subtractor 87 outputs a result obtained by subtracting the multiplication result from the even-sample-side corrected analog-digital conversion result.
- the subtraction result is input to the correction coefficient search unit 85 as “error e”.
- the correction coefficient search unit 85 searches for the correction coefficient and the attenuation factor estimated value a EST based on the error e, the digital output of the digital output generation inverse processing unit 82, and the odd-sample-side corrected analog-digital conversion result.
- the search result is output to the odd sample side digital correction unit 83, the even sample side digital correction unit 84, and the multiplication unit 86.
- the odd sample side digital correction unit 83, the even sample side digital correction unit 84, the correction coefficient search unit 85, the multiplication unit 86, and the subtraction unit 87 constitute a correction unit 20b.
- the digital output generation inverse processing unit 82 separates at least the upper bit raw output (for example, D 1 to D 5 ) and the lower bit raw output binary composite value D BE (D BackEnd). It is possible to calculate.
- the correction coefficients W 1 to W 5 and W BE are searched using these as in the first embodiment and the correction is performed based on the results.
- bit raw output D i can be calculated accurately depends on variations and DC offset voltage of the comparison voltage in the internal circuit of the analog-to-digital conversion unit 811.
- the output of the successive approximation analog-digital converter is the raw output D i (binary: ⁇ 1) itself of the analog-digital conversion unit. Therefore, the digital output generation inverse processing unit 82 as shown in FIG. 8 is unnecessary. In this case, correction can be performed in the same manner as in other embodiments (for example, in the case of FIG. 2A).
- the original input signal voltage VIN is input to the pipeline analog-digital converter 81 as in the first embodiment.
- the pipeline analog-digital conversion unit 81 performs analog-digital conversion on the input signal voltage VIN
- the digital output b i is input to a digital output generation inverse processing unit (RDEC) 82.
- the digital output generation inverse processing unit (RDEC) 82 outputs, for example, D 1 to D 5 and the binary composite value D BE of the raw output of the lower bits.
- the even sample side digital correction unit 84 performs the calculation of Expression (20) using these outputs and the correction coefficients W i and W BE obtained by searching in the correction operation mode.
- the even-sample-side digital correction unit 84 performs the calculation of Expression (20) for all samples regardless of whether the samples are odd-numbered or even-numbered samples, and the output D OUT is a digital correction type in the normal operation mode. It becomes the output of the whole analog-digital converter.
- FIG. 10 is a schematic diagram showing a configuration example of the analog-digital converter according to the eighth embodiment of the present invention.
- the analog-digital converter of FIG. 10 has a configuration in which the odd sample side digital correction unit 24 and the even sample side digital correction unit 25 in FIG. 2A of Embodiment 1 are replaced with one digital correction unit 101 in the correction unit 20c. ing.
- the odd-numbered sample side digital correction unit and the even-numbered sample side digital correction unit are separately provided.
- FIG. It can be implemented as one digital correction unit. This makes it possible to reduce the circuit scale of the correction unit on mounting.
- the multiplication unit 27 outputs a multiplication result of the corrected analog-digital conversion result corresponding to the odd-numbered sample among the corrected analog-digital conversion results and the attenuation rate estimation value a EST supplied from the correction coefficient search unit 26. .
- the subtractor 28 outputs a result obtained by subtracting the multiplication result of the multiplier 27 from the corrected analog-digital conversion result corresponding to the even-numbered sample among the corrected analog-digital conversion results.
- the subtraction result is input to the correction coefficient search unit 26 as “error e”.
- the coefficient Wi and the attenuation rate estimated value a EST are searched, and the search result is output to the digital correction unit 101 and the multiplication unit 27.
- the operation in the normal operation mode is the same as that in the first embodiment, and correction is performed by the digital correction unit 101 regardless of odd-numbered samples and even-numbered samples.
- FIG. 11 is a schematic diagram showing a configuration example of the analog-digital converter according to the ninth embodiment of the present invention.
- the digital correction method of the present embodiment is applied to a system having two analog-digital conversion units.
- the voltage of the correction signal is attenuated by the attenuation circuit in one analog-digital conversion unit, and the voltage of the correction signal is attenuated by the attenuation circuit in the other analog-digital conversion unit.
- FIG. 11 shows a configuration related to the correction operation mode, and an original input signal voltage application mechanism to the two analog-to-digital converters is the same as in the first embodiment and the like is omitted. ing.
- an attenuation circuit (for example, a resistance voltage dividing circuit) 21 is connected to the correction signal application terminal.
- the voltage of the correction signal (first analog voltage) is applied to the analog-digital converter [1] (first analog-digital converter) 111, and the output voltage (second analog voltage) of the attenuation circuit 21 is analog-digital.
- the data is input to the conversion unit [2] (second analog / digital conversion unit) 112.
- the digital correction unit [1] 113 includes the digital output D i (1) of the analog-digital conversion unit [1] 111 and the correction coefficient [1] (first correction coefficient) W i (1 ) supplied from the correction coefficient search unit 26. ) , The corrected analog-digital conversion result [1] (first corrected digital signal) is output.
- the digital correction unit [2] 114 includes the digital output D i (2) of the analog-digital conversion unit [2] 112 and the correction coefficient [2] (second correction coefficient) W i (2 ) supplied from the correction coefficient search unit 26. ) , The corrected analog-to-digital conversion result [2] (second corrected digital signal) is output.
- the multiplication unit 27 outputs the multiplication result of the corrected analog-digital conversion result [1] and the attenuation factor estimated value a EST supplied from the correction coefficient search unit 26.
- the subtraction unit (error detection unit) 28 outputs a result obtained by subtracting the multiplication result of the multiplication unit 27 from the corrected analog-digital conversion result [2].
- the subtraction result is input to the correction coefficient search unit 26 as “error e”.
- Correction coefficient searching unit 26 the error e, and the digital output D i of the analog-to-digital converter unit [1] 111 (1), and the digital output D i of the analog-to-digital converter unit [2] 112 (2), the corrected analog Based on the digital conversion result [1], the correction coefficient [1] W i (1) , the correction coefficient [2] W i (2), and the attenuation rate estimated value a EST are searched.
- the search result is output to the digital correction unit [1] 113, the digital correction unit [2] 114, and the multiplication unit 27.
- the correction coefficient [1] W i (1) , the correction coefficient [2] W i (2), and the attenuation factor estimated value a EST are expressed by the following equations (21) to ( It is searched by the algorithm of 26).
- the original input signal voltages are respectively input to the analog-digital conversion unit [1] 111 and the analog-digital conversion unit [2] 112.
- the digital correction unit [1] 113 performs correction according to the equation (21) using the correction coefficient [1] Wi (1) obtained by searching in the correction operation mode, and the corrected digital output that is the correction result
- the signal D out (1) is output as the first analog-digital conversion output.
- the digital correction unit [2] 114 performs correction according to Expression (22) using the correction coefficient [2] W i (2) obtained by searching in the correction operation mode, and the correction that is the correction result is performed.
- the post-digital output signal D out (2) is output as the second analog-digital conversion output.
- the analog-digital converter of the ninth embodiment the same effects as those of the first embodiment can be obtained, and in particular, the analog-digital converter [1] 111 and the analog-digital converter [2] 112 Power consumption and circuit area can be significantly reduced.
- the resolution of the analog-digital conversion unit [1] 111 and the resolution of the analog-digital conversion unit [2] 112 are set to the same M bits. However, these resolutions do not have to be the same, and various The same applies to the combination of resolutions.
- the present invention made by the present inventor has been specifically described based on the embodiment.
- the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention.
- the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described.
- a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. .
- the correction operation mode and the normal operation mode are provided here, in some cases, the correction coefficient may be searched for in the normal operation mode. That is, with respect to the original input signal voltage VIN , the attenuation signal voltage is generated by the attenuation circuit 21, and the input signal voltage VIN and the attenuation signal voltage are input. Search, update, and reflection may be performed as appropriate.
- each bit value D i constituting the digital output is not necessarily binary. For example, in the case of a pipeline analog-digital converter, it takes three values (1, 0, ⁇ 1), seven values (3, 2, 1, 0, ⁇ 1, ⁇ 2, ⁇ 3).
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Abstract
Description
《アナログデジタル変換器の概略構成》
図2Aは、本発明の実施の形態1によるアナログデジタル変換器において、その構成例を示す概略図である。図2Bは、図2Aのアナログデジタル変換部に入力されるアナログ信号の一例を示す波形図である。図2Aにおいて、補正用信号印加端子には減衰回路21が接続され、経路切換えマルチプレクサ(第1選択回路)22の2個の入力ノードには、それぞれ補正用信号印加端子と減衰回路21の出力ノードが接続される。経路切換えマルチプレクサ22の出力は、アナログデジタル変換部(ADC)23に入力される。減衰回路21は、この例では、抵抗分圧回路で構成される。
補正用信号(第1アナログ信号)は、図2Bに示した「補正用信号波形」の通り、階段状に変化する複数(この例では3通り)のアナログ電圧(第1アナログ電圧)V1~V3を持ち、各アナログ電圧の値は、アナログデジタル変換周期の2周期間ずつ正確に保持される。アナログデジタル変換部23には、図2Bに示した「ADC入力波形」の通り、アナログデジタル変換周期の奇数番目では補正用信号の電圧(V1~V3)が直接入力され、偶数番目では、減衰回路21を介して補正用信号をa倍に減衰した電圧(第2アナログ電圧)(aV1~aV3)が入力される。制御部30は、このような「ADC入力波形」となるように、経路切換えマルチプレクサ22を選択する。具体的には、制御部30は、補正用信号の各サイクル毎に、各サイクル内の一部(ここでは半分)の期間で補正用信号を選択し、残りの期間で減衰回路21からの出力信号(第2アナログ信号)を選択する。
以上のような方式を用いた場合、例えば、減衰回路21の減衰率が設計値aからばらついてaREALとなったとしても、隣接する奇数番目サンプルと偶数番目サンプルのアナログデジタル変換部23への入力電圧比は厳密に一定値aREALになる。ここで、本実施の形態の方式では、減衰率推定値(減衰係数)aESTも探索しているため、減衰回路21の減衰率がaREALとなったとしても、減衰率推定値aESTがaREALに収束することで、減衰率ばらつきの影響を吸収し、補正係数Wiの正確な探索を維持できる。その結果、減衰回路21は、線形性さえ良好であれば、減衰率が設計値からばらついても特に問題は無く、この線形性は、抵抗分圧回路を代表とする受動素子を用いた減衰回路21では十分に保証される。
図2Aの補正ユニット20aでは、奇数サンプル側デジタル補正部24の出力においてaESTを乗算する構成としたが、偶数サンプル側デジタル補正部25の出力においてaESTを乗算してもよい。その場合、aESTの探索値は、減衰回路21の減衰率aではなく、その逆数1/aになるが、所望の補正係数Wiを同様に探索できる。また、この場合、式(3)~(5)のかわりに、以下の式(13)~(15)のアルゴリズムで探索を行えばよい。
以上の説明は、アナログデジタル変換器が例えば補正動作モードで動作する場合の説明である。補正動作モードでは、図2Aの制御部30は、入力経路用スイッチ(入力スイッチ)29をオフに制御した状態で、経路切換えマルチプレクサ(第1選択回路)22の選択を行い、補正ユニット20aに補正係数Wiの探索を行わせる。本実施の形態によるアナログデジタル変換器は、このような補正動作モードに加えて、通常動作モードを備える。
《補正用信号の生成方式[1]》
図3Aは、本発明の実施の形態2によるアナログデジタル変換器において、その構成例を示す概略図である。図3Bは、図3Aにおける主要部の動作例を示すタイミングチャートである。図3Aのアナログデジタル変換器は、図2Aの構成例と比較して、その補正用信号を生成する方式の詳細が示されたものとなっている。アナログデジタル変換部23やその後段の補正ユニット20aの構成および動作に関しては、図2Aと図3Aとで特に違いはないため、詳細な説明は省略する。
《補正用信号の生成方式[2]》
図4Aは、本発明の実施の形態3によるアナログデジタル変換器において、その構成例を示す概略図である。図4Bは、図4Aにおける主要部の動作例を示すタイミングチャートである。図4Aのアナログデジタル変換器は、図2Aの構成例と比較して、その補正用信号を生成する方式の詳細が示されたものとなっている。アナログデジタル変換部23やその後段の補正ユニット20aの構成および動作に関しては、図2Aと図4Aとで特に違いはないため、詳細な説明は省略する。
《補正用信号の生成方式[3]》
図5Aは、本発明の実施の形態4によるアナログデジタル変換器において、その構成例を示す概略図である。図5Bは、図5Aにおける主要部の動作例を示すタイミングチャートである。図5Aのアナログデジタル変換器は、図2Aの構成例と比較して、その補正用信号を生成する方式の詳細が示されたものとなっている。アナログデジタル変換部23やその後段の補正ユニット20aの構成および動作に関しては、図2Aと図5Aとで特に違いはないため、詳細な説明は省略する。
《補正用信号の生成方式[4]》
図6は、本発明の実施の形態5によるアナログデジタル変換器において、それに含まれる補正用信号生成部の構成例を示す概略図である。図6に示す補正用信号生成部34dは、抵抗ラダー型の構成となっており、実施の形態2の図3Aに示した補正用信号生成部34aの変形例となっている。
《補正用信号の生成方式[5]》
図7は、本発明の実施の形態6によるアナログデジタル変換器において、それに含まれる補正用信号生成部周りの構成例を示す概略図である。図7に示す補正用信号生成部34eは、抵抗ラダー型の構成となっており、実施の形態2の図3Aに示した補正用信号生成部34aの変形例となっている。ここでは、図3Aの場合と異なり、アナログデジタル変換部23が差動回路構成である場合を例としている。
《アナログデジタル変換器の概略構成(変形例[1])》
図8は、本発明の実施の形態7によるアナログデジタル変換器において、その一部の構成例を示す概略図である。本実施の形態8では、例えば、市販のチップ部品となるパイプラインアナログデジタル変換器に、本実施の形態によるデジタル補正方式を適用する場合の一例について説明する。図8において、アナログデジタル変換部81よりも前段の構成は、他の実施の形態の構成と同様である。
図8の構成において、補正動作モード時には、実施の形態1などと同様に、補正係数Wi,WBEと減衰率推定値aESTの探索を、式(17)~(19)および式(3)、(5)によるアルゴリズムで行う。
《アナログデジタル変換器の概略構成(変形例[2])》
図10は、本発明の実施の形態8によるアナログデジタル変換器において、その構成例を示す概略図である。図10のアナログデジタル変換器は、補正ユニット20cにおいて、実施の形態1の図2Aにおける奇数サンプル側デジタル補正部24と偶数サンプル側デジタル補正部25を一つのデジタル補正部101で置換した構成となっている。前述した実施の形態1~4および7では、奇数サンプル側デジタル補正部と偶数サンプル側デジタル補正部を別々に備えているが、これらは、実際に実装する際には、図10のように、一つのデジタル補正部として実装することが可能である。これによって、実装上の補正ユニットの回路規模を低減することなどが可能になる。
《アナログデジタル変換器の概略構成(変形例[3])》
図11は、本発明の実施の形態9によるアナログデジタル変換器において、その構成例を示す概略図である。本実施の形態9では、2つのアナログデジタル変換部を持つシステムに対して本実施の形態のデジタル補正方式を適用する場合について説明する。この場合、図11に示すように、補正動作モード時に、一方のアナログデジタル変換部には補正用信号の電圧を、他方のアナログデジタル変換部には補正用信号の電圧を減衰回路で減衰した電圧を印加することで、実施の形態1などと同様の原理にもとづいて補正係数の探索を行うことが可能である。なお、図11では、補正動作モード時に関連する構成が示されており、2つのアナログデジタル変換部への本来の入力信号電圧の印加機構などは、実施の形態1などと同様であるので省略されている。
21 減衰回路
22 経路切換えマルチプレクサ
23 アナログデジタル変換部
24 奇数サンプル側デジタル補正部
25 偶数サンプル側デジタル補正部
26 補正係数探索部
27 乗算部
28 減算部
29 入力経路用スイッチ
30 制御部
31 抵抗ラダー型マルチ電圧生成部
32 セレクタ
33 選択信号生成部
34a~34e 補正信号生成部
41 デジタルアナログ変換部
42 DAC経路用スイッチ
43 2分周器
51 サンプルアンドホールド回路
52 S/H経路用スイッチ
61 初段抵抗ラダー
62 セレクタ[1]
63 次段抵抗ラダー
64 セレクタ[2]
71P セレクタ[P](セレクタ正相側)
71N セレクタ[N](セレクタ逆相側)
72P 並列抵抗[P](並列抵抗正相側)
72N 並列抵抗[N](並列抵抗逆相側)
73A~73D 減衰回路用の抵抗
74 経路切換えマルチプレクサ
75 反転用マルチプレクサ
76 分周器
81 パイプラインアナログデジタル変換部
811 アナログデジタル変換ユニット
812 デジタル出力生成部
82 デジタル出力生成逆処理部
83 奇数サンプル側デジタル補正部
84 偶数サンプル側デジタル補正部
85 補正係数探索部
86 乗算部
87 減算部
101 デジタル補正部
111 アナログデジタル変換部[1]
112 アナログデジタル変換部[2]
113 デジタル補正部[1]
114 デジタル補正部[2]
Claims (15)
- それぞれ電圧値が異なる複数の第1アナログ電圧が順次入力され、前記複数の第1アナログ電圧を所定の減衰率で減衰させることで複数の第2アナログ電圧を順次出力する減衰回路と、
前記第1アナログ電圧と前記第1アナログ電圧を減衰した前記第2アナログ電圧とを組とする複数組の第1および第2アナログ電圧が順次入力され、前記複数組の第1および第2アナログ電圧の中のそれぞれのアナログ電圧を異なるタイミングで選択して出力する第1選択回路と、
前記第1選択回路から出力される前記複数組の第1および第2アナログ電圧を複数組の第1および第2デジタル信号にそれぞれ変換するアナログデジタル変換部と、
前記複数組の第1および第2デジタル信号に基づいて、前記複数組の第1および第2デジタル信号のM(Mは1以上の整数)個のビットに対してそれぞれ乗算するM個の補正係数を探索する補正ユニットと、
を有する、アナログデジタル変換器。 - 請求項1記載のアナログデジタル変換器において、
前記減衰回路は、抵抗分圧回路または容量分圧回路で構成される、アナログデジタル変換器。 - 請求項2記載のアナログデジタル変換器において、
前記補正ユニットは、
前記複数組の第1および第2デジタル信号の各組毎に、前記第1および第2デジタル信号の前記M個のビットに対してそれぞれ前記M個の補正係数を乗算することで第1および第2補正後デジタル信号を生成するデジタル補正部と、
前記第1補正後デジタル信号か前記第2補正後デジタル信号のいずれか一方に前記減衰率に対応して設けられた減衰係数を乗算することで第3デジタル信号を生成する乗算部と、
前記第1補正後デジタル信号に前記減衰係数を乗算する場合は前記第3デジタル信号と前記第2補正後デジタル出力信号との誤差を検出し、前記第2補正後デジタル信号に前記減衰係数を乗算する場合には前記第3デジタル信号と前記第1補正後デジタル出力信号との誤差を検出する誤差検出部と、
前記複数組の第1および第2デジタル信号の各組毎に前記誤差検出部で検出される誤差がゼロに近づくように前記M個の補正係数を探索する補正係数探索部と、を有する、アナログデジタル変換器。 - 請求項3記載のアナログデジタル変換器において、
前記補正係数探索部は、さらに、前記複数組の第1および第2デジタル信号の各組毎に前記誤差検出部で検出される誤差がゼロに近づくように前記減衰係数を探索する、アナログデジタル変換器。 - 請求項3記載のアナログデジタル変換器において、
前記第1選択回路は、各入力サイクル毎にそれぞれ組が異なる前記第1および第2アナログ電圧が入力され、前記各入力サイクル内の一部の期間で前記第1アナログ電圧を選択し、残りの期間で前記第2アナログ電圧を選択する、アナログデジタル変換器。 - 請求項3記載のアナログデジタル変換器において、さらに、
前記複数の第1アナログ電圧を生成する補正用信号生成部と、
オンに制御された際に、前記アナログデジタル変換部に所定のアナログ入力電圧を入力する入力スイッチと、
補正動作モードおよび通常動作モードと、を備え、
前記アナログデジタル変換器は、
前記補正動作モードでは、前記入力スイッチをオフに制御し、前記アナログデジタル変換部に前記第1選択回路で選択されたアナログ電圧を入力することで前記M個の補正係数を探索し、
前記通常動作モードでは、前記第1選択回路の出力を開放状態に、前記入力スイッチをオンにそれぞれ制御し、前記アナログデジタル変換部を用いて前記所定のアナログ入力電圧を所定のデジタル信号に変換し、前記デジタル補正部を用いて前記所定のデジタル信号を前記補正動作モードで探索された前記M個の補正係数で補正し、当該補正結果となる補正後デジタル出力信号を出力する、アナログデジタル変換器。 - 請求項6記載のアナログデジタル変換器において、
前記補正用信号生成部は、
所定の固定電圧を分圧する補正用抵抗分圧回路と、
前記補正用抵抗分圧回路に含まれる複数の抵抗分圧ノードのいずれかを順次選択することで前記複数の第1アナログ電圧を順次生成する第2選択回路と、を備える、アナログデジタル変換器。 - 請求項6記載のアナログデジタル変換器において、
前記補正用信号生成部は、
複数の選択スイッチを含み、所定の固定電圧を複数のノードに選択的に印加する第3選択回路と、
一端が前記減衰回路の入力ノードに共通に接続され、他端が前記第3選択回路の前記複数のノードにそれぞれ接続される複数の並列抵抗と、を備え、
前記複数の選択スイッチの中からオンに制御する単数または複数の選択スイッチを順次定めることで前記減衰回路の入力ノードに前記複数の第1アナログ電圧を順次生成する、アナログデジタル変換器。 - 請求項6記載のアナログデジタル変換器において、
前記補正用信号生成部は、デジタルアナログ変換部で構成される、アナログデジタル変換器。 - それぞれ電圧値が異なる複数の第1アナログ電圧が順次入力され、前記複数の第1アナログ電圧を所定の減衰率で減衰させることで複数の第2アナログ電圧を順次出力する減衰回路と、
前記第1アナログ電圧と前記第1アナログ電圧を減衰した前記第2アナログ電圧とを組とする複数組の第1および第2アナログ電圧の中の複数の前記第1アナログ電圧を複数の第1デジタル信号にそれぞれ変換する第1アナログデジタル変換部と、
前記複数組の第1および第2アナログ電圧の中の複数の前記第2アナログ電圧を複数の第1デジタル信号にそれぞれ変換する第2アナログデジタル変換部と、
前記第1および第2アナログデジタル変換部で変換された前記複数組の第1および第2デジタル信号に基づいて、前記複数の第1デジタル信号のM(Mは1以上の整数)個のビットに対してそれぞれ乗算するM個の第1補正係数と、前記複数の第2デジタル信号のM個のビットに対してそれぞれ乗算するM個の第2補正係数とをそれぞれ探索する補正ユニットと、
を有する、アナログデジタル変換器。 - 請求項10記載のアナログデジタル変換器において、
前記減衰回路は、抵抗分圧回路または容量分圧回路で構成される、アナログデジタル変換器。 - 請求項11記載のアナログデジタル変換器において、
前記補正ユニットは、
前記複数組の第1および第2デジタル信号の各組毎に、前記第1デジタル信号の前記M個のビットに対してそれぞれ前記M個の第1補正係数を乗算することで第1補正後デジタル信号を生成する第1デジタル補正部と、
前記複数組の第1および第2デジタル信号の各組毎に、前記第2デジタル信号の前記M個のビットに対してそれぞれ前記M個の第2補正係数を乗算することで第2補正後デジタル信号を生成する第2デジタル補正部と、
前記第1補正後デジタル信号か前記第2補正後デジタル信号のいずれか一方に前記減衰率に対応して設けられた減衰係数を乗算することで第3デジタル信号を生成する乗算部と、
前記第1補正後デジタル信号に前記減衰係数を乗算する場合は前記第3デジタル信号と前記第2補正後デジタル出力信号との誤差を検出し、前記第2補正後デジタル信号に前記減衰係数を乗算する場合には前記第3デジタル信号と前記第1補正後デジタル出力信号との誤差を検出する誤差検出部と、
前記複数組の第1および第2デジタル信号の各組毎に前記誤差検出部で検出される誤差がゼロに近づくように前記M個の第1および第2補正係数を探索する補正係数探索部と、を有する、アナログデジタル変換器。 - 各サイクル毎に異なる電圧値に設定される第1アナログ信号が入力され、前記第1アナログ信号を所定の減衰率で減衰させることで第2アナログ信号を生成する減衰回路と、
前記第1および第2アナログ信号が入力され、前記各サイクル毎に、前記各サイクル内の一部の期間で前記第1アナログ信号を選択して出力し、残りの期間で前記第2アナログ信号を選択して出力する第1選択回路と、
前記各サイクル毎に、前記第1選択回路から出力される前記第1アナログ信号を第1デジタル信号に変換し、前記第1選択回路から出力される前記第2アナログ信号を第2デジタル信号に変換するアナログデジタル変換部と、
前記各サイクル毎の前記第1および第2デジタル信号に基づいて、前記第1および第2デジタル信号のM(Mは1以上の整数)個のビットに対してそれぞれ乗算するM個の補正係数を探索する補正ユニットと、
を有する、アナログデジタル変換器。 - 請求項13記載のアナログデジタル変換器において、
前記減衰回路は、抵抗分圧回路または容量分圧回路で構成される、アナログデジタル変換器。 - 請求項14記載のアナログデジタル変換器において、
前記補正ユニットは、
前記各サイクル毎に、前記第1および第2デジタル信号の前記M個のビットに対してそれぞれ前記M個の補正係数を乗算することで第1および第2補正後デジタル信号を生成するデジタル補正部と、
前記第1補正後デジタル信号か前記第2補正後デジタル信号のいずれか一方に前記減衰率に対応して設けられた減衰係数を乗算することで第3デジタル信号を生成する乗算部と、
前記第1補正後デジタル信号に前記減衰係数を乗算する場合は前記第3デジタル信号と前記第2補正後デジタル出力信号との誤差を検出し、前記第2補正後デジタル信号に前記減衰係数を乗算する場合には前記第3デジタル信号と前記第1補正後デジタル出力信号との誤差を検出する誤差検出部と、
前記各サイクル毎に、前記誤差検出部で検出される誤差がゼロに近づくように前記M個の補正係数を探索する補正係数探索部と、を有する、アナログデジタル変換器。
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JPWO2014207870A1 (ja) | 2017-02-23 |
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