JP3311182B2 - High-speed high-precision AD converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed, high-resolution, high-precision A / D converter, in which the influence of an error in an A / D conversion code caused by a temperature change is corrected and stabilized.

[0002]

2. Description of the Related Art Since a high-speed, high-resolution AD converter is not commercially available, a circuit is constituted by two low-resolution, high-speed AD converters, and a high-resolution, high-speed AD converter is equivalently realized. are doing. As an example of the prior art, there is an example of an AD converter having a sampling rate of several MHz and a resolution of 18 bits. This will be described with reference to FIGS.

As shown in FIG. 5, the circuit includes a reference signal source 40, changeover switches 42 and 43, a reference digital voltmeter 44, a high-speed and high-precision AD converter 50, a calibration signal 82, and a controller. 80.

The reference signal source 40 is a highly stable reference voltage signal source for supplying analog voltages at a plurality of points for calibrating the high-speed and high-precision AD conversion unit 50. The signal is supplied to the high-speed and high-precision AD converter 50, and receives a control signal from the controller 80 and outputs a desired voltage. The changeover switch 42 is for switching to the reference signal source 40 side when the original analog signal under test 100 is measured, and during calibration. The changeover switch 43 is a switch for supplying the same voltage signal from the reference signal source 40 to both the high-speed and high-accuracy AD converter 50 and the reference digital voltmeter 44 for measurement.

The calibration signal 82 detects a change in the ambient temperature of the entire measurement system including the other measurement system to a desired temperature, for example, a temperature change of 3 ° C. or more, temporarily stops the entire measurement system, and stops the other measurement system. And a start signal for acquiring and executing a temperature correction parameter in order to perform temperature calibration and bring the accuracy of the entire measurement system into a desired allowable accuracy range.
The measurement of the D conversion unit is temporarily stopped and calibration is performed. The reference digital voltmeter 44 is a voltage measuring device serving as a reference for measuring a constant voltage of the reference signal source 40 with high accuracy. And supplies the same analog voltage to the control unit 80.

The control unit 80 has, for example, a high-speed digital operation function using a DSP. When the analog signal 100 to be measured is measured, the control unit 80 receives continuous 18-bit data from the high-speed and high-precision AD conversion unit 50, and 80-out code data of 18-bit resolution data with high accuracy by reducing the influence of temperature by performing the characteristic correction and offset correction calculation processing
Is output. The control unit 80 performs calibration when a desired temperature change is made by the calibration signal 82, acquires a temperature correction parameter, converts the temperature correction parameter into correction data, and stores the data in the internal memory as a temperature correction parameter. That is, by switching the changeover switches 42 and 43, the same analog constant voltage from the reference signal source 40 is measured at each of a plurality of points, and the code data value of the high-speed and high-precision AD converter 50 is changed to the value of the reference digital voltmeter 44. A temperature correction parameter that matches is obtained. That is, the control unit 80 compares the two and finds the deviation of the high-speed and high-precision AD conversion unit 50, and from this, calculates the offset correction amount and the amplifier gain correction amount. Thereby, the calibration value of the temperature correction is updated. As described above, when the temperature exceeds the desired temperature difference, the measurement is temporarily stopped, the calibration is performed at the temperature, and the measurement is always performed while maintaining high AD conversion accuracy.

The high-speed and high-precision AD converter 50 receives the analog signal to be measured 100, converts the analog signal to an 18-bit resolution at a sampling rate of several MHz, and outputs code data 50out. As shown in (1), it is composed of a high-speed sample and hold unit 51, a first AD converter 52, a DA converter 54, an error amplifier 56, a second AD converter 60, and an adder 62.

The input analog signal 50in is sampled for each clock by the sample and hold section 51, and the held analog signal 51a is supplied to the first AD converter 52 and one input terminal of the error amplifier 56. First AD converter 52
Is a high-speed AD converter with 8-bit resolution, for example. As a result, the analog signal 51a is converted into code data 52d, and then supplied to the DA converter 54 and one input terminal of the adder 62. The D / A converter 54 uses a highly accurate D / A converter in order to obtain the analog amount of the remaining difference after the quantization conversion. As a result, the signal is DA-converted into an analog signal, and then supplied to the other input terminal of the error amplifier 56.
In this circuit system, no error occurs due to the first AD converter 52. Instead, the conversion accuracy of the DA converter 54 causes an error.

The error amplifier 56 subtracts the analog signal quantized by the first AD converter 52 from the analog signal 51a, and amplifies the remaining difference signal by, for example, several tens times the analog signal 56a to the second AD converter. 60. The second AD converter 60 converts the remaining analog signal 56a equivalent to ± 0 to ± 2 LSB converted by the first AD converter 52 into a digital signal. A 12-bit resolution high-speed AD converter is used in consideration of the code conversion deviation. After receiving the analog signal 56a and converting it to digital code data 60d, it is supplied to the other input terminal of the adder 62.

The adder 62 includes code data 52d obtained by shifting up the weight of the first AD converter 52 by 10 bits,
The code data 60d of the second AD converter 60 is added, and
The code data 50out with 18-bit resolution is calculated.
This data is supplied to the control unit 80, and the output code data 80out as a result of performing a correction operation using both the offset and gain temperature correction parameters in the control unit 80 is converted into a high-precision AD conversion with a temperature corrected 18-bit resolution. Obtained as data.

[0011]

As described above, since the high-speed and high-precision A / D converter 50 is composed of individual analog circuits, it is sensitive to temperature changes. In the correction means based on the calibration at each temperature change interval, an error may occur during this period, and a highly accurate AD converter may not always be maintained. Therefore, the problem to be solved by the present invention is to provide an independent temperature sensor separately from the calibration signal 82 and add a means for continuously correcting the temperature, without stopping the measurement.
It is another object of the present invention to realize a high-speed and high-accuracy AD converter with stable accuracy.

[0012]

FIGS. 1 and 2 show a first solution according to the present invention. In order to solve the above problem, in the configuration of the present invention, the temperature sensor 12 for detecting the temperature of the high-speed and high-precision AD conversion circuit is provided, and the error amplifier 56 and the adder 62 In the meantime, the configuration means is provided with a continuous temperature correction unit 20 for continuously correcting the temperature. As a result, receiving the analog signal under measurement 100, the high-speed sample-and-hold unit 51, the first AD converter 52 having a low resolution and high speed, and the DA converter 54
, An error amplifier 56, a low-resolution high-speed second AD converter 60, and an adder 62, thereby realizing a high-speed, high-resolution AD conversion circuit with further improved temperature stability.

The continuous temperature compensator 20 receives the temperature signal from the temperature sensor 12, converts the temperature signal into a digital signal, and supplies the first memory 16 and the AD converter 14 for supplying an address signal to the second memory 18. A first memory 16 for receiving digital temperature data from the AD converter 14 and reading out a correction value of the temperature drift and supplying the correction value to the offset adder 22; , The temperature correction value of the amplification degree is read out and the multiplier 24
A second memory 18 for supplying to the first memory 16
The offset adder 22 receives the correction value of the temperature drift from the second AD converter 60 and the code data 20in from the second AD converter 60, adds the both, corrects the offset deviation, and supplies the offset to one input terminal of the multiplier 24. And the second memory 1
8, the temperature correction value of the amplification degree from the offset adder 22
There is a configuration unit that includes a multiplier 24 that receives the code data from, and multiplies and normalizes the two, and outputs the code data 20out in which the deviation of the amplification degree is corrected.

FIGS. 3 and 4 show a second solution according to the invention. In order to solve the above problem, in the configuration of the present invention, the temperature sensor 12 for detecting the temperature of the high-speed and high-precision AD conversion circuit section is provided, and the error amplifier 56 and the second AD converter 60 In addition, the configuration means is provided with a continuous temperature correction unit 21 for continuously correcting the temperature.

The continuous temperature compensator 21 receives the temperature signal from the temperature sensor 12, converts the temperature signal into a digital signal, and supplies the first memory 16 and the AD converter 14 that supplies an address signal to the second memory 18. A first memory 16 for receiving digital temperature data from the AD converter 14 and reading out a correction value of the temperature drift and supplying the correction value to the offset adder 22; , The temperature correction value of the amplification degree is read out and the multiplier 24
A second memory 18 for supplying to the first memory 16
And a D / A converter 26 that receives the signal from the second memory 18 and converts the signal into an analog signal to output an offset correction signal 26add. The signal from the second memory 18 is converted to an analog signal and converted into an analog signal. There is a configuration means for providing a DA converter 28 that outputs 28mul.

[0016]

In the first embodiment, the offset adder 22 and the first memory 16 provide an operation of correcting an offset deviation due to a temperature drift of the error amplifier 56, the second AD converter 60, and the DA converter 54. In the first embodiment, the multiplier 24 and the second memory 18 use the error amplifier 5
6, the second AD converter 60 and the DA converter 54
The effect of correcting the influence error of the equivalent gain fluctuation due to the temperature drift is obtained. In the second embodiment, the error amplifier 56 and the second A
The effect of correcting the offset deviation due to the temperature drift of the D converter 60 and the DA converter 54 can be obtained. In the second embodiment, the second AD converter 6 is controlled by the analog gain correction signal 28mul by the second memory 18 and the DA converter 28.
By finely adjusting the reference voltage of 0, an effect of correcting the influence error of the gain variation of the error amplifier 56 and the equivalent gain variation due to the temperature drift of the second AD converter 60 and the DA converter 54 can be obtained.

By providing the temperature sensor 12, the high-speed and high-precision A / D converter 10 corrects the temperature of the factor that causes the output data to fluctuate depending on the temperature. And a high-speed and high-accuracy AD converter with continuously stable accuracy can be realized.

[0018]

【Example】

(Embodiment 1) In the embodiment of the present invention, a high-speed and high-resolution (18 bits) for continuously correcting a minute temperature by providing a temperature sensor.
Is an example of an AD converter. In this regard, FIGS. 1 and 2
This will be described with reference to FIG.

This circuit uses the conventional high-speed and high-precision A shown in FIG.
With respect to the circuit configuration of the D conversion unit 50, as shown in FIG.
The continuous temperature correction unit 20 is added between the second AD converter 60 and the adder 62 to constitute the high-speed and high-accuracy AD converter 10. The high-speed and high-accuracy A / D converter 10 receives the analog voltage of the input analog signal 50in, performs A / D conversion, adds a minute temperature correction, and outputs high-accuracy code data 50out. The continuous temperature correction unit 20 is provided with the temperature sensor 12 and continuously outputs code data with minute temperature correction. The temperature sensor 12 and the AD converter 1
4, a first memory 16, a second memory 18, an offset adder 22, and a multiplier 24.

The temperature sensor 12 is installed near the high-speed and high-precision AD converter 10 which fluctuates sensitively to a temperature change, supplies a temperature signal to the AD converter 14 and converts the temperature signal into a digital signal. It is supplied to the address input terminals of the first memory 16 and the second memory 18 as an address signal in units of 0.2 ° C.

As the first minute correction, the offset adder 22 and the first memory 16 correct the offset deviation caused by the temperature drift of the error amplifier 56, the second AD converter 60 and the DA converter 54 caused by the minute temperature change. I do. That is, the first memory 16 previously stores a parameter for correcting the offset deviation caused by the temperature change, and stores the offset correction amount data corresponding to the unit temperature change of 0.2 ° C. from the first memory 16. The data is read and supplied to one input terminal of the offset adder 22. The second input terminal of the offset adder 22 has the second AD
The code data 20in from the converter 60 is supplied, and by adding the two, the offset deviation caused by the temperature change is corrected and output to the multiplier 24.

As the second minute correction, the multiplier 24 and the second memory 18 correct the fluctuation of the equivalent gain of the error amplifier 56, the DA converter 54, and the second AD converter 60 caused by the minute temperature change. That is, a parameter for correcting a gain deviation caused by a temperature change is stored in the second memory 18 in advance, and a corresponding gain correction amount data is read from the second memory 18 in accordance with a unit temperature change, and a multiplier is read. 24 to one input terminal. Then, the signal from the offset adder 22 is supplied to the other input terminal of the multiplier 24, and the signal is multiplied and normalized to obtain the code data 20out in which the gain deviation caused by the temperature change is corrected. Output. For the parameters stored in the first memory 16 and the second memory 18, the temperature characteristics are measured in advance, and the corresponding correction data values are stored in each memory.

(Embodiment 2) In the embodiment of the present invention, there is an example of a high-speed, high-resolution AD converter for providing a temperature sensor and performing minute temperature correction by an analog correction method. about this,
This will be described with reference to FIGS. This circuit performs the offset correction by applying the analog offset correction signal 26add to the error amplifier 56 as shown in FIG. 3 with respect to the circuit configuration of the first embodiment shown in FIG. A high-speed and high-precision AD conversion unit 11 that continuously performs minute temperature correction by changing the voltage and performing gain correction is configured.

The continuous temperature correction section 21 receives the signal from the temperature sensor 12 and continuously performs an analog offset correction signal 26add for minute temperature correction and an analog gain correction signal 2
8mul, and outputs the temperature sensor 12 and AD
A converter 14, a first memory 16, a second memory 18,
D / A converters 26 and 28 are provided. To correct the first offset, the correction amount data for correcting the offset deviation caused by the temperature change from the first memory 16 is stored in the first memory 16.
After being read from the memory 16 and supplied to the DA converter 26 to be converted into an analog offset correction signal 26add, this is supplied to one input terminal of the error amplifier 56. As a result, the offset-corrected analog signal is supplied to the second AD converter 60.

In the second gain correction, correction amount data for correcting a gain deviation caused by a temperature change is read from the second memory 18. This is supplied to a DA converter 28 and the analog gain correction signal 28
After the conversion to mul, the reference voltage of the second AD converter 60 is finely adjusted, so that gain adjustment is equivalently realized. As a result, the gain-corrected code data is output from the second AD converter 60. By these corrections, similarly to the first embodiment, the code data 50out in which offset and gain deviations caused by minute temperature changes are corrected.
Is output.

The offset adder 22, the multiplier 24 and the adder 62 for performing the digital operation of the above embodiment may be constituted by a circuit, or may be constituted by a high-speed operation processing device such as a DSP.

[0027]

Since the present invention is configured as described above, it has the following effects. In the first embodiment, the offset adder 22 and the first memory 1
6, the error amplifier 56, the second AD converter 60 and the DA
The effect of correcting the offset deviation due to the temperature drift of converter 54 is obtained. In the first embodiment, the multiplier 24
The second memory 18 has an effect of correcting an error caused by a variation in gain of the error amplifier 56 and a variation in equivalent gain due to a temperature drift of the second AD converter 60 and the DA converter 54.

In the second embodiment, the first memory 16 and the DA
The error amplifier 56 and the second AD converter 6
The effect of correcting the offset deviation due to 0 or the temperature drift of the DA converter 54 can be obtained. In the second embodiment, the reference voltage of the second AD converter 60 is finely adjusted by the analog gain correction signal 28mul by the second memory 18 and the DA converter 28, so that the gain variation of the error amplifier 56, the second AD converter 60 and the DA The effect of correcting the influence error of the equivalent gain fluctuation due to the temperature drift of converter 54 is obtained.

As a whole, a temperature sensor 12 is provided,
The high-speed and high-precision A / D converter 10 corrects the temperature of the factor that the output data fluctuates depending on the temperature, so that the temperature can be corrected even for a small temperature change. A simple AD converter can be realized.

[0030]

[Brief description of the drawings]

FIG. 1 shows a high-speed and high-precision AD converter 1 according to a first embodiment of the present invention.
0 is a circuit configuration diagram of FIG.

FIG. 2 is a circuit configuration diagram of a continuous temperature correction unit 20 according to the first embodiment of the present invention.

FIG. 3 shows a high-speed and high-precision AD converter 1 according to a second embodiment of the present invention.
1 is a circuit configuration diagram of FIG.

FIG. 4 is a circuit configuration diagram of a continuous temperature correction unit 21 according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional measurement system including a calibration system for performing high-speed, high-precision AD conversion of the analog signal under measurement 100.

FIG. 6 is a circuit configuration diagram of a conventional high-speed and high-precision AD converter 50.

[Explanation of symbols]

10, 50, 11 High-speed and high-precision AD converter 12 Temperature sensor 14 AD converter 16 First memory 18 Second memory 20, 21 Continuous temperature corrector 20in, 20out, 80out, 50out, 52d, 60d
Code data 22 Offset adder 24 Multiplier 26add Analog offset correction signal 26, 54, 28 DA converter 28mul Analog gain correction signal 40 Reference signal source 42, 43 Changeover switch 44 Reference digital voltmeter 50in Input analog signal 51 Sample hold unit 51a , 56a analog signal 52 first AD converter 56 error amplifier 60 second AD converter 62 adder 80 control unit 82 calibration signal 100 analog signal to be measured

Claims (4)

(57) [Claims] 1. A high-speed sample-and-hold unit (51) receiving a measured analog signal (100), a first A / D converter (52) with low resolution and high speed, and a D / A converter (54).
, An error amplifier (56), and a second resolution 2A that has a low resolution and a high speed
A high-speed, high-resolution A / D conversion circuit having a D converter (60) and an adder (62), a temperature sensor (12) for detecting the temperature of the high-speed, high-precision A / D conversion circuit section; A continuous temperature compensator (20) for continuously compensating the temperature between the error amplifier (56) and the adder (62) in response to the signal from the temperature sensor (12); High-speed, high-precision AD converter characterized by the following. 2. The continuous temperature compensator (20) according to claim 1, wherein
Receives the temperature signal from the temperature sensor (12), converts it into a digital signal, and converts the digital signal into a first memory (16) and a second memory (1).
8) An AD converter (14) for supplying an address signal to the AD converter is provided. Upon receiving the digital temperature data from the AD converter (14), a correction value of the temperature drift is read from the first memory (16) and offset. A first memory (16) to be supplied to the adder (22) is provided. Upon receiving digital temperature data from the AD converter (14), a temperature correction value of the amplification degree is read from the second memory (18) and multiplied. A second memory (18) for supplying the temperature drift correction value from the first memory (16) and the code data (20) from the second AD converter (60);
in), an offset adder (22) is added to correct the offset shift by adding the two, and the offset adder (22) is supplied to one input terminal of the multiplier (24), and the amplification from the second memory (18) is performed. Temperature correction value
A multiplier (24) is provided which receives the code data from the offset adder (22), multiplies the two, normalizes the output, and outputs the code data (20out) corrected for the deviation of the amplification degree. A high-speed, high-precision A / D converter. 3. A high-speed sample-and-hold section (51) receiving an analog signal to be measured (100), a first AD converter (52) with low resolution and high speed, and a DA converter (54).
, An error amplifier (56), and a second resolution 2A that has a low resolution and a high speed
A high-speed and high-resolution A / D conversion circuit having a D converter (60) and an adder (62), a temperature sensor (12) for detecting the temperature of a high-speed and high-precision A / D conversion circuit section; Upon receiving the signal from the sensor (12), the error amplifier (5
6) The second AD converter (60) is provided with a continuous temperature correction section (21) for continuously correcting the temperature, and the above-mentioned configuration is provided. 4. The continuous temperature compensator according to claim 3, wherein:
Receives the temperature signal from the temperature sensor (12), converts it into a digital signal, and converts the digital signal into a first memory (16) and a second memory (1).
8) An AD converter (14) for supplying an address signal to the AD converter is provided. Upon receiving the digital temperature data from the AD converter (14), a correction value of the temperature drift is read from the first memory (16) and offset. A first memory (16) to be supplied to the adder (22) is provided. Upon receiving digital temperature data from the AD converter (14), a temperature correction value of the amplification degree is read from the second memory (18) and multiplied. A second memory (18) for supplying a signal to the device (24); receiving a signal from the first memory (16), DA converting the signal into an analog signal, and outputting an offset correction signal (26add); 26), and a DA converter (28) that receives a signal from the second memory (18), converts the signal into an analog signal, and outputs a gain correction signal (28mul). Specially And the high-speed high-precision AD converter.