Aperture delay calibration circuit and method for multi-channel analog-to-digital converter

Abstract

The present invention discloses a calibration circuit and method for the aperture delay of a multi-channel analog-to-digital converter, belonging to the technical field of integrated circuits. The calibration circuit includes: a configurable delay circuit, a sampling and holding circuit, an analog-to-digital conversion circuit, and an aperture delay calculation circuit. When the chip is calibrated for aperture delay, an input signal and a sampling clock signal are externally applied to each channel of the multi-channel analog-to-digital converter, which is converted into a digital coding result by the analog-to-digital conversion circuit after passing through the sampling and holding circuit, and output to the aperture delay calculation circuit to calculate the delay configuration word, and input to the configurable delay circuit to compensate for the aperture delay. The method of the present invention converts the problem of measuring the aperture delay deviation between channels into the deviation of the analog-to-digital conversion output result between channels, performs simultaneous calibration of multiple chips without the need for additional circuits, and realizes automatic calibration of the aperture delay inside the chip by adding an aperture delay calculation circuit inside the chip, thereby reducing the requirements for test equipment, test time and cost, and improving test efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of analog-to-digital conversion and calibration, and in particular to a calibration circuit and method for aperture delay of a multi-channel analog-to-digital converter. Background Art

[0002] As a bridge between the physical world and the digital world, analog-to-digital converters are widely used in industrial monitoring, power transmission and other fields. The analog-to-digital converter is driven by an external clock to sample and convert the input signal. Due to the delay in signal transmission, the input signal sampled and held by the analog-to-digital converter is usually delayed from the ideal input signal.

[0003] In synchronous sampling or direct I / Q demodulation applications, the aperture delays of two or more ADCs must be well matched to ensure that the input signals of the same phase are sampled. Aperture delay mismatch between converters will cause errors in fast rotating signals. Traditional aperture delay calibration generally uses a high-speed oscilloscope to measure the phase difference between the sampling clock and the sampled input signal to obtain the calibration result, which has the problems of long test time and high test cost. At the same time, traditional aperture delay calibration requires the host computer to control the chip and write the calibration configuration word. The test process is complicated and cumbersome, and the traditional aperture delay calibration method cannot achieve simultaneous calibration of multiple chips. Summary of the invention

[0004] The problem to be solved by the present invention is: in view of the problem of mismatch in aperture delay between different channels of a traditional multi-channel analog-to-digital converter, the present invention proposes a calibration circuit and method for the aperture delay of a multi-channel analog-to-digital converter, which can be used for simultaneous calibration of multiple chips and greatly improves the test efficiency.

[0005] The present invention adopts the following technical solution: a calibration circuit for aperture delay of a multi-channel analog-to-digital converter, comprising: a configurable delay circuit, a sampling and holding circuit, an analog-to-digital conversion circuit, and an aperture delay calculation circuit;

[0006] An input signal and a sampling clock signal are applied to each channel of a multi-channel analog-to-digital converter, the sampling clock signal is input into a sampling and holding circuit via a configurable delay circuit, the input signal is directly input into the sampling and holding circuit, and is input into an analog-to-digital conversion circuit after being sampled and held by the sampling and holding circuit to be converted into a digital coding result; the digital coding result after conversion of each channel is output to an aperture delay calculation circuit, the coding deviation and the delay configuration word are calculated, and the aperture delay is compensated by the configurable delay circuit; the configurable delay circuit inputs the compensation result back into the sampling and holding circuit, and the calibration of the aperture delay of the multi-channel analog-to-digital converter is automatically completed after multiple iterations.

[0007] Preferably, the input signal is a ramp signal or a sinusoidal signal, and the higher the frequency of the input signal, the higher the calibration accuracy.

[0008] Preferably, the delay circuit can be configured to set up a multi-stage buffer, each stage of the buffer is controlled by a switch, and the sampling clock signal passes through the multi-stage buffer in sequence to generate different delay signals.

[0009] Preferably, the configurable delay circuit also includes a decoder, and the aperture delay calculation circuit calculates the delay configuration word of each channel and inputs it into the corresponding decoder. After decoding by the decoder, one switch of the configurable delay circuit is controlled to be closed, and one delayed signal is output as a delayed sampling clock to the sample and hold circuit.

[0010] Preferably, the aperture delay calculation circuit includes an add-subtract counter and a threshold comparator, the add-subtract counter automatically calculates the coding deviation of the input channel conversion results, and the threshold comparator compares the deviation result with a preset threshold.

[0011] Preferably, when the encoding deviation is zero or less than a preset threshold, the multi-channel analog-to-digital converter aperture delay calibration is completed.

[0012] The technical solution of the present invention also includes: a method for calibrating aperture delay of a multi-channel analog-to-digital converter, comprising the following steps:

[0013] S1, when the host computer issues an instruction to calibrate the aperture delay of the chip, the input signal and the sampling clock signal are applied to each channel of the multi-channel analog-to-digital converter respectively, and the multi-channel analog-to-digital converter performs analog-to-digital conversion on the input signal to obtain the digital coding result of each channel;

[0014] S2. Since the aperture delays of the analog-to-digital converters of the multiple channels are inconsistent, there are deviations in the conversion results of the analog-to-digital converters of the multiple channels. The digital coding results after conversion of each channel are output to the aperture delay calculation circuit, and the deviations of the conversion results between the channels are calculated.

[0015] S3, the aperture delay calculation circuit determines the size relationship of the aperture delays between the channels according to the conversion result deviation between the channels, and calculates the delay configuration word of the configurable delay circuit;

[0016] S4, the configurable delay circuit compensates the aperture delay according to the delay configuration word, thereby reducing the aperture delay mismatch between multiple channels;

[0017] S5, repeating steps S1 to S4, after multiple iterations, determining whether to continue the aperture delay calibration, and completing the calibration when the conversion result deviations of each channel are less than a preset threshold.

[0018] Preferably, in step S1, the input signal is calculated according to the input signal range of the multi-channel analog-to-digital converter and the aperture delay mismatch time between channels, and the formula is as follows:

[0019] ;

[0020] Where f is the input signal frequency, t is the time, V FS represents the peak-to-peak value of the input signal, Indicates the value of the applied input signal.

[0021] Preferably, in step S3, the aperture delay calculation circuit calculates the coding deviation between the digital coding results obtained by conversion of each channel in the following manner:

[0022] ;

[0023] in, represents the aperture delay difference between channels, Respectively represent t and The sampling voltage at the moment, represents the rate of change of the input signal, D represents the difference in output codes of analog-to-digital converters of different channels due to the aperture delay difference, They represent the output codes of analog-to-digital converters of different channels respectively.

[0024] Preferably, in step S3, the method for calculating the delay configuration word is: setting the initial value of the aperture delay configuration word of each channel to zero, and adding 1 to the delay configuration word of the channel with the smallest aperture delay during the calibration process until the aperture delay difference between the channels is less than a threshold, then the calibration is terminated.

[0025] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0026] 1. The multi-channel analog-to-digital converter aperture delay calibration circuit and method of the present invention converts the problem of measuring the aperture delay deviation between channels into the deviation of the analog-to-digital conversion output results between channels. It is not necessary to use high-precision test equipment to measure the phase difference between the sampling clock and the sampled input signal, thereby reducing the requirements for the test equipment without the need for additional circuits.

[0027] 2. The present invention realizes automatic calibration of the aperture delay inside the chip by adding an aperture delay calculation circuit, thereby reducing the test time and cost. When calibrating the aperture delay of the chip, only an input signal and a sampling clock signal need to be applied externally, and multiple chips can be calibrated simultaneously, greatly improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The structure block diagram of the calibration circuit for the aperture delay of the multi-channel analog-to-digital converter of the present invention;

[0029] Figure 2 This is a block diagram of the configurable delay circuit structure of the present invention;

[0030] Figure 3 The present invention is a flow chart of a method for calibrating aperture delay of a multi-channel analog-to-digital converter. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the application is further elaborated in detail below in conjunction with the accompanying drawings. The described embodiments are only a part of the embodiments involved in the present invention. All non-innovative embodiments of other researchers in the field on this embodiment belong to the protection scope of the present invention. At the same time, for the step numbering in the embodiment of the present invention, it is only set for the convenience of explanation, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0032] In one embodiment of the present invention, a calibration circuit for aperture delay of a multi-channel analog-to-digital converter is provided. Figure 1 As shown, it includes: a configurable delay circuit, a sample-and-hold circuit, an analog-to-digital conversion circuit, and an aperture delay calculation circuit;

[0033] The input signal and the sampling clock signal are applied to each channel of the multi-channel analog-to-digital converter, wherein the sampling clock signal is input into the sample-and-hold circuit through a configurable delay circuit, and the input signal is directly input into the sample-and-hold circuit, sampled and held by the sample-and-hold circuit, and then input into the analog-to-digital conversion circuit, which converts the signal into a digital coding result.

[0034] Due to inconsistent aperture delays, there are deviations in the conversion results of multiple channel analog-to-digital converters. The digital coding results after conversion of each channel are output to the aperture delay calculation circuit. The configuration word of the configurable delay circuit is obtained according to the deviation between the conversion results, and the conversion results are output to the configurable delay circuit.

[0035] The configurable delay circuit compensates the aperture delay according to the coding deviation and the delay configuration word, and inputs the compensation result back to the sampling and holding circuit to reduce the aperture delay mismatch between multiple channels.

[0036] After multiple iterations, when the conversion result deviation of the multiple channels is less than a preset threshold, the calibration of the aperture delay of the multi-channel analog-to-digital converter is automatically completed.

[0037] Preferably, a delay circuit may be configured in this embodiment, such as Figure 2 As shown, the configurable delay circuit is provided with multiple buffers, each buffer is controlled by a switch, the sampling clock signal generates different delay signals through the multiple buffers, the aperture delay calculation circuit calculates the delay configuration word of each channel, the delay configuration word is decoded by the decoder to control the closure of a switch, and outputs a delay signal as a delayed sampling clock to the sample and hold circuit.

[0038] Preferably, the aperture delay calculation circuit in this embodiment is composed of a simple addition and subtraction counter and a threshold comparator. The digital coding result of each channel is input into the aperture delay calculation circuit. The coding deviation of the input conversion result of each channel is automatically calculated by the addition and subtraction counter. The deviation result is compared with the preset threshold value by the threshold comparator. No host computer is required for control, and the chip area is small. When the coding deviation is zero or less than the preset threshold value, the multi-channel analog-to-digital converter aperture delay calibration is completed.

[0039] Furthermore, this embodiment realizes automatic calibration of aperture delay inside the chip based on the above-mentioned multi-channel analog-to-digital converter aperture delay calibration circuit, such as Figure 3 As shown, the following steps are included:

[0040] S1, when the host computer issues an instruction to calibrate the aperture delay of the chip, the input signal and the sampling clock signal are applied to each channel of the multi-channel analog-to-digital converter respectively, and the multi-channel analog-to-digital converter performs analog-to-digital conversion on the input signal to obtain the digital coding result of each channel;

[0041] S2. Since the aperture delays of the analog-to-digital converters of the multiple channels are inconsistent, there are deviations in the conversion results of the analog-to-digital converters of the multiple channels. The digital coding results after conversion of each channel are output to the aperture delay calculation circuit, and the deviations of the conversion results between the channels are calculated.

[0042] S3, the aperture delay calculation circuit determines the size relationship of the aperture delays between the channels according to the conversion result deviation between the channels, and calculates the delay configuration word of the configurable delay circuit;

[0043] S4, the configurable delay circuit compensates the aperture delay according to the delay configuration word and the sampling clock, thereby reducing the aperture delay mismatch between multiple channels;

[0044] S5, repeating steps S1 to S4, after multiple iterations, determining whether to continue the aperture delay calibration, and completing the calibration when the conversion result deviations of each channel are less than a preset threshold.

[0045] In step S1, the input signal is calculated according to the input signal range of the multi-channel analog-to-digital converter and the aperture delay mismatch time between channels. Taking a 16-bit multi-channel analog-to-digital converter as an example, the input signal range is -10V~10V. Assuming that the aperture delay mismatch between channels is 2ns, the input signal applied is:

[0046]

[0047] It should be noted that, in this embodiment, the input signal may be a ramp signal or a sinusoidal signal. Within the bandwidth of the sampling and holding circuit, and provided that no dynamic settling error occurs, the higher the frequency of the input signal, the higher the calibration accuracy.

[0048] In step S2, the aperture delay mismatch between the channels of the multi-channel analog-to-digital converter causes different input signals sampled by ADCs of different channels, thereby causing deviations in digital output results.

[0049] The aperture delay calculation circuit calculates the code deviation between the digital code results obtained by conversion of each channel, and the method is as follows:

[0050]

[0051] The digital output coding deviation is the largest when the input signal passes through the midpoint. The maximum coding deviation is:

[0052] 3.14mV / ns*2ns=6.28mV=20LSB

[0053] The aperture delay is compensated according to the output coding deviation. When the output coding deviation is zero or less than a threshold, it indicates that the calibration is completed. In this embodiment, the aperture delay deviation can be calibrated to a minimum of 100 ps.

[0054] In summary, the present invention proposes an aperture delay calibration circuit and method for a multi-channel analog-to-digital converter, which converts the problem of measuring the aperture delay deviation between channels into the deviation of the analog-to-digital conversion output results between channels. It does not need to use high-precision test equipment to measure the phase difference between the sampling clock and the sampling input signal, and reduces the requirements for the test equipment without the need for additional circuits. At the same time, by adding an aperture delay calculation circuit inside the chip, the aperture delay is automatically calibrated inside the chip, reducing the test time and cost. When calibrating the aperture delay of the chip, only the input signal and the sampling clock signal need to be applied externally, so it is very convenient to calibrate multiple chips at the same time, greatly improving the test efficiency.

[0055] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multi-channel analog-to-digital converter aperture delay calibration circuit, characterized in that: include: Configurable delay circuit, sample-and-hold circuit, analog-to-digital conversion circuit, and aperture delay calculation circuit; Apply an input signal and a sampling clock signal to each channel of a multi-channel analog-to-digital converter, the sampling clock signal is input to a sampling and holding circuit through a configurable delay circuit, the input signal is directly input to the sampling and holding circuit, and is input to an analog-to-digital conversion circuit after being sampled and held by the sampling and holding circuit, and converted into a digital coding result; output the digital coding result after conversion of each channel to an aperture delay calculation circuit, the aperture delay calculation circuit calculates the coding deviation between the digital coding results obtained by conversion of each channel, determines the size relationship of the aperture delay between each channel, calculates the delay configuration word of the configurable delay circuit, and compensates the aperture delay through the configurable delay circuit; The aperture delay calculation circuit includes an add-subtract counter and a threshold comparator. The add-subtract counter automatically calculates the encoding deviation of the input conversion results of each channel, and the threshold comparator compares the deviation result with a preset threshold. The configurable delay circuit inputs the compensation result back to the sampling and holding circuit, and automatically completes the calibration of the aperture delay of the multi-channel analog-to-digital converter after multiple iterations.

2. The multi-channel analog-to-digital converter aperture delay calibration circuit according to claim 1, characterized in that: The input signal is a ramp signal or a sinusoidal signal. The higher the input signal frequency is, the higher the calibration accuracy is.

3. The multi-channel analog-to-digital converter aperture delay calibration circuit according to claim 1, characterized in that: The configurable delay circuit is provided with a multi-stage buffer, each stage of the buffer is controlled by a switch, and the sampling clock signal passes through the multi-stage buffer in sequence to generate different delay signals.

4. The multi-channel analog-to-digital converter aperture delay calibration circuit according to claim 3, characterized in that: The configurable delay circuit also includes a decoder. The aperture delay calculation circuit calculates the delay configuration word of each channel and inputs it into the corresponding decoder. After decoding by the decoder, one switch of the configurable delay circuit is controlled to be closed, and one delayed signal is output as a delayed sampling clock to the sample-and-hold circuit.

5. The multi-channel analog-to-digital converter aperture delay calibration circuit according to claim 4, characterized in that: When the encoding deviation is zero or less than a preset threshold, the multi-channel analog-to-digital converter aperture delay calibration is completed.

6. A method for calibrating aperture delay of a multi-channel analog-to-digital converter, applied to the calibration circuit according to any one of claims 1 to 5, characterized in that: The steps include: S1, when the host computer issues an instruction to calibrate the aperture delay of the chip, the input signal and the sampling clock signal are applied to each channel of the multi-channel analog-to-digital converter respectively, and the multi-channel analog-to-digital converter performs analog-to-digital conversion on the input signal to obtain the digital coding result of each channel; S2. Since the aperture delays of the analog-to-digital converters of the multiple channels are inconsistent, there are deviations in the digital coding results obtained by the analog-to-digital converters of the multiple channels. The digital coding results after conversion of each channel are output to the aperture delay calculation circuit, and the coding deviations between the conversion results of each channel are calculated. S3, the aperture delay calculation circuit determines the size relationship of the aperture delays between the channels according to the coding deviation between the conversion results of the channels, and calculates the delay configuration word of the configurable delay circuit; S4, the configurable delay circuit compensates the aperture delay according to the delay configuration word, thereby reducing the aperture delay mismatch between multiple channels; S5, repeating steps S1 to S4, after multiple iterations, determining whether to continue the aperture delay calibration, and completing the calibration when the conversion result deviations of each channel are less than a preset threshold.

7. The method for calibrating aperture delay of a multi-channel analog-to-digital converter according to claim 6, characterized in that: The input signal is calculated based on the input signal range of the multi-channel analog-to-digital converter and the aperture delay mismatch time between channels, and the formula is as follows: ； Where f is the input signal frequency, t is the time, V FS represents the peak-to-peak value of the input signal, Indicates the value of the applied input signal.

8. The method for calibrating aperture delay of a multi-channel analog-to-digital converter according to claim 7, characterized in that: The aperture delay calculation circuit calculates the coding deviation between the digital coding results obtained by conversion of each channel in the following way: ； in, represents the aperture delay difference between channels, Represent t and The sampling voltage at the moment, represents the rate of change of the input signal, D represents the difference in output codes of analog-to-digital converters of different channels due to the aperture delay difference, They represent the output codes of analog-to-digital converters of different channels respectively.

9. The method for calibrating aperture delay of a multi-channel analog-to-digital converter according to claim 8, characterized in that: In step S3, the delay configuration word is calculated, and the initial value of the aperture delay configuration word of each channel is zero. During the calibration process, the delay configuration word of the channel with the smallest aperture delay is increased by 1 until the aperture delay difference between channels is less than the threshold, and then the calibration is terminated.

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