ΔΣ AD converter and sensor device

Abstract

To provide a ΔΣ AD converter and a sensor device that have a small circuit scale and a high conversion accuracy.SOLUTION: A ΔΣ AD converter comprises a ΔΣ AD modulator 12, an accumulation unit 13, a counting part 20, an adjustment value storage part 30, a first adder 14, a cumulative value latch part 15, and a control circuit 40. When a count value C inputted from the counting part 20 reaches a predetermined value, the control circuit 40 outputs to the adjustment value storage part 30 a signal for designating a temperature region depending on an adjustment cumulative value Z inputted from the first adder 14. The adjustment value storage part 30 outputs to the first adder 14 and the counting part 20 an adjustment value for an offset value and an adjustment value for the count value depending on the signal. The control circuit 40 outputs a latch signal to the cumulative value latch part 15 in response to termination of counting of the counting part 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ΔΣ AD converter and a sensor device. [Background technology]

[0002] FIG. 4 is a block diagram showing the configuration of a conventional high-precision digital temperature sensor device. The temperature sensor device 500 includes an analog temperature sensor 50 , a ΔΣ AD converter 51 , a digital filter 52 , a comparator 53 , back-end scaling 54 , and a reference voltage circuit 55 .

[0003] In the conventional temperature sensor device 500, the analog temperature sensor 50 and the ΔΣ AD converter 51 have inherent gain / offset. Therefore, the raw digital data output from the digital filter 52 is subjected to error reduction by applying different gain / offset corresponding to different temperatures by the comparator 53 and back-end scaling 54.

[0004] Specifically, the digital data of the digital filter 52 is compared with threshold data in a comparator 53, and adjusted by a gain / offset corresponding to a region determined in back-end scaling 54 (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2011-527009 Summary of the Invention [Problem to be solved by the invention]

[0006] However, back-end scaling 54, which adjusts raw digital data with gain / offset, requires a multiplication circuit, which increases the circuit size. Furthermore, if the number of digits of the multiplication coefficient is increased to achieve higher precision, the circuit size of the multiplication circuit will increase even further. Therefore, in the conventional temperature sensor device 500, the circuit Occupied area There is a problem that the number of people increases and costs become higher.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide a ΔΣ AD converter and a sensor device that have a small circuit scale and high conversion accuracy. [Means for solving the problem]

[0008] The ΔΣ AD converter of the present invention is A ΔΣ AD converter that converts an input analog signal into a digital signal, a ΔΣAD modulator that receives the analog signal and outputs a modulated signal; an accumulator that accumulates the modulated signals and outputs an accumulated value; a counting unit that counts a set count value; an adjustment value storage unit in which adjustment values ​​of the count value and adjustment values ​​of the offset value are stored; a first adder that outputs an adjusted cumulative value obtained by adding the cumulative value and an adjustment value of the offset value; a cumulative value latch unit to which the adjusted cumulative value is input; a control circuit that receives the adjusted cumulative value, a count value from the counting unit, and a threshold value of the adjusted cumulative value that determines a temperature range from the adjusted value storage unit, and outputs a control signal to the counting unit and the latch signal to the cumulative value latch unit; Equipped with the control circuit determines the temperature range in accordance with the adjusted cumulative value input from the first adder when the count value input from the counting unit reaches a predetermined value, and outputs a signal specifying the temperature range to the adjusted value storage unit; an adjustment value storage unit outputs an adjustment value of the offset value and an adjustment value of the count value according to the specified temperature range to the first adder and the counting unit; The control circuit outputs the latch signal to the cumulative value latch section upon receipt of the completion of counting by the counter section. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a ΔΣ AD converter and a sensor device that have a small circuit scale and high conversion accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a sensor device according to an embodiment of the present invention; [Figure 2] 10 is a graph showing an example of the relationship between the temperature and the cumulative value of the sensor device of the present embodiment. [Figure 3] FIG. 10 is a block diagram showing another example of the sensor device of the present embodiment. [Figure 4] FIG. 1 is a block diagram showing a conventional sensor device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] FIG. 1 is a block diagram showing a sensor device according to this embodiment. The sensor device 100 includes a sensor 1 and a ΔΣ AD converter. The ΔΣ AD converter includes a count value storage unit 10, an offset value storage unit 11, a ΔΣ AD modulator 12, an accumulator 13, an adder 14, an accumulated value latch unit 15, a multiplexer 16, adders 17 and 18, a counting unit 20, an adjustment value storage unit 30, and a control circuit 40. These circuits operate in response to a clock signal, but are not shown in the drawings or explained here.

[0013] The sensor 1 outputs an analog signal X corresponding to the measured physical information (e.g., temperature) to the ΔΣAD modulator 12. The ΔΣAD modulator 12 modulates the analog signal X and outputs it to the accumulator 13. The accumulator 13 outputs an accumulated value Y corresponding to the analog signal X to the adder 14. The adder 14 adds the accumulated value Y of the accumulator 13 to the offset value of the adder 18 to output an adjusted accumulated value Z. The count value storage unit 10 stores the initial value of the count value. The offset value storage unit 11 stores the initial value of the offset value. The adjustment value storage unit 30 stores a threshold value of the adjusted accumulated value Z that determines the temperature range when adjustment is performed, as well as an adjustment value of the count value and an adjustment value of the offset value that correspond to that range. The adder 17 adds the count value of the counter 20 and the adjustment value of the count value of the adjustment value storage unit 30 to output an adjusted count value. The adder 18 adds the initial value of the offset value in the offset value storage unit 11 and the adjusted value of the offset value in the adjustment value storage unit 30 and outputs the result. The counter unit 20 loads the count value and counts down the count value in response to a control signal from the control circuit 40. The control circuit 40 receives the count value from the counter unit 20, the adjusted cumulative value Z from the adder 14, and the threshold value of the adjusted cumulative value Z, which determines the temperature range when adjustment is performed, from the adjustment value storage unit 30, and outputs a control signal to the multiplexer 16, the counter unit 20, the adjustment value storage unit 30, and the accumulated value latch unit 15. When the multiplexer 16 receives a control signal from the control circuit 40 at its control terminal, it outputs either the initial value of the count value in the count value storage unit 10 or the adjusted count value of the adder 17. When the accumulated value latch unit 15 receives a latch signal from the control circuit 40 at its control terminal, it latches the adjusted cumulative value Z output by the adder 14 and outputs a signal Z, which is the output signal of the sensor device 100, from its output terminal. N Output.

[0014] When the ΔΣAD modulator 12 is, for example, a first-order ΔΣAD modulator and outputs a binary value of "0" and "1," the density of the output data "1" is uniform and temperature-dependent. The accumulator 13 accumulates the data output by the ΔΣAD modulator 12 and outputs an accumulated value Y. An offset value is added to the accumulated value Y by the adder 14, and the accumulated value Y is input to the accumulated value latch unit 15 as an adjusted accumulated value Z. That is, the adjusted accumulated value Z is primarily corrected by the initial value of the count value and the initial value of the offset value.

[0015] The analog signal X corresponding to the physical information (for example, temperature) output by the sensor 1 and the characteristics of the ΔΣ modulator 12 are generally second-order or higher nonlinear characteristics, and therefore accuracy cannot be guaranteed by first-order correction. Therefore, the ΔΣ AD converter of this embodiment corrects the accumulated value Y output by the accumulator 13 using broken line approximation. In other words, the ΔΣ AD converter of this embodiment can guarantee accuracy by correcting the nonlinear characteristics of the analog signal X and the ΔΣ modulator 12 together.

[0016] Specifically, the control circuit 40 calculates the adjusted cumulative value Z when the count value C counts down a predetermined value M (for example, 1 / 2 of the initial value). M and the threshold value of the adjusted cumulative value Z, the temperature range is determined, and the selected adjusted value is specified in the adjusted value storage unit 30. The adjusted value storage unit 30 outputs the adjusted value specified by the control circuit 40. The adder 17 outputs a new count value obtained by adding the adjusted value to the count value M. The multiplexer 16 outputs the new count value input from the adder 17 in response to an instruction from the control circuit 40. The counting unit 20 loads the new count value and starts counting down in response to an instruction from the control circuit 40. The adder 18 outputs a new offset value obtained by adding the adjusted value of the offset value to the initial value of the offset value. The adder 14 outputs an adjusted cumulative value Z obtained by adding the new offset value to the cumulative value Y. When the counting unit 20 has finished counting down the new count value, the control circuit 40 outputs a latch signal to the cumulative value latch unit 15 to generate a digital signal Z. N is determined. In other words, the adjusted cumulative value Z is subjected to a new primary correction using the adjusted count value and adjusted offset value corresponding to the temperature range, and therefore the nonlinear characteristics are corrected using piecewise linear approximation. The piecewise linear approximation correction of the adjusted cumulative value Z as described above can be achieved by using an accumulation-type ΔΣ AD converter.

[0017] The operation of the sensor device 100 of this embodiment will be described below with reference to the drawings. When the sensor device 100 is started, the ΔΣAD modulator 12, the accumulator 13, the counting unit 20, etc. are reset, but this is omitted from the drawings and explanation.

[0018] 2 is a graph showing an example of the relationship between the temperature of the sensor device of this embodiment and the adjusted cumulative value Z. The solid line shows an example of a case where the adjusted cumulative value Z output by the adder 14 does not have linearity with respect to temperature. The dashed line shows the characteristics when the adjusted cumulative value Z has linearity with respect to temperature. The vertical dotted line indicates the threshold value of the adjusted cumulative value Z with respect to temperature, and the area separated by the vertical dotted line is the temperature region.

[0019] The control circuit 40 outputs a control signal of "0" from the output terminal 46 to the control terminal of the multiplexer 16. When the control signal of "0" is input, the multiplexer 16 selects and outputs the initial value of the count value output by the count value storage unit 10. The offset value storage unit 11 outputs the initial value of the offset value. Next, the control circuit 40 outputs a control signal instructing "load" from the output terminal 45 to the control terminal 22 of the counting unit 20. When the control signal instructing "load" is input, the counting unit 20 inputs the initial value of the count value from the input terminal 21 and loads it into an internal register. The control circuit 40 loads the threshold value of the adjusted cumulative value Z for determining the temperature range from the output terminal 32 of the adjustment value storage unit 30 via the input terminal 42. Here, the initial value of the count value (e.g., 1000) and the initial value of the offset value are values ​​corresponding to the dashed lines in FIG. 2.

[0020] The control circuit 40 outputs a control signal instructing "countdown" from the output terminal 45 to the control terminal 22 of the counting unit 20. When the control signal instructing "countdown" is input, the counting unit 20 starts counting down in response to the clock signal and outputs the count value from the output terminal 23. The ΔΣAD modulator 12 outputs the analog signal X output by the sensor 1 as "0" and "1" data to the accumulator 13 in response to the clock signal. The accumulator 13 outputs a cumulative total value Y obtained by accumulating the data in response to the clock signal to the adder 14. The adder 18 outputs the initial value of the offset value. The adder 14 outputs an adjusted cumulative total value Z obtained by adding the cumulative total value Y and the initial value of the offset value to the cumulative total latch unit 15. At this time, the cumulative total latch unit 15 does not receive a latch signal from the control circuit 40, so Digital signal Z N Do not output.

[0021] The control circuit 40 outputs a control signal instructing "count down" from the output terminal 45 to the control terminal 22 of the counting unit 20. When the control signal instructing "count down" is input, the counting unit 20: clock The ΔΣAD modulator 12 starts counting down in response to the signal and outputs the count value from the output terminal 23. clock In response to the signal, the sensor 1 outputs an analog signal X as "0" or "1" data to the accumulator 13. The accumulator 13 clock In response to the signal, the adder 18 outputs a cumulative value Y obtained by accumulating the data to the adder 14. The adder 18 outputs the initial value of the offset value. The adder 14 outputs an adjusted cumulative value Z obtained by adding the cumulative value Y and the initial value of the offset value to the cumulative value latch unit 15. At this time, the cumulative value latch unit 15 does not output the digital signal Z because it has not received a latch signal from the control circuit 40.

[0022] The above process is the first primary correction of the cumulative total value Y of the sensor device 100. Next, a new primary correction of the cumulative total value Y will be described. As an example, the adjusted cumulative total value Z when the count value C reaches a predetermined value M (for example, 1 / 2 of the initial value) is M The case where is the value shown by the dotted line in FIG. 2 will be described.

[0023] When the count value C input from the counting unit 20 to the input terminal 41 reaches a predetermined value M (for example, 500), the control circuit 40 adjusts the adjusted cumulative value Z input from the adder 14 to the input terminal 43. M The temperature range is determined from the threshold value of the cumulative adjustment value Z, and the adjustment value to be selected is determined. In Figure 2, the adjusted cumulative value Z when the count value M is M When the value indicated by the dotted line (a) is the adjusted cumulative value Z M is the value indicated by the dotted line (b), and selects the temperature range (1) of 100°C to 120°C. Then, the control circuit 40 outputs a signal specifying the temperature range (1) from the output terminal 44 to the input terminal 31 of the adjustment value storage unit 30.

[0024] When the adjustment value storage unit 30 receives a signal specifying the temperature region (1) at the input terminal 31, it outputs an adjustment value (for example, −200) for the count value from the output terminal 33 and outputs an adjustment value for the offset value from the output terminal . Adder 17 outputs an adjusted count value (e.g., 300) obtained by adding the adjustment value of the count value to count value M to multiplexer 16. Adder 18 outputs an adjusted offset value obtained by adding the adjustment value of the offset value to the initial value of the offset value to adder 14.

[0025] The control circuit 40 outputs a control signal "1" from the output terminal 46 to the multiplexer 16, and then outputs a control signal from the output terminal 45 to the control terminal 22 of the counting unit 20 to instruct "load". When a control signal instructing "load" is input to the counting unit 20, the counting unit 20 receives the adjusted count value output by the multiplexer 16 from the input terminal 21 and loads it into an internal register. Next, when a control signal instructing "count down" is input to the control terminal 22 from the output terminal 45 of the control circuit 40, the counting unit 20 clock In response to the signal, the countdown is restarted and the count value is output from output terminal 23. Adder 14 outputs to cumulative value latch unit 15 an adjusted cumulative value Z obtained by adding cumulative value Y and the adjusted offset value.

[0026] In this way, a new primary correction of the cumulative value Y is started, and together with the first primary correction, an adjusted cumulative value Z can be obtained in which the nonlinear characteristics have been corrected by broken-line approximation. Specifically, since the initial count value is 1000 and the adjusted count value is 800, the curve (1) is corrected to the approximately straight line (2). Then, the approximately straight line (2) is corrected to the approximately straight line (3) by the adjustment offset value. In other words, the offset adjustment value is determined so as to ensure the continuity of the adjusted cumulative value Z.

[0027] When the count value C input from the counting unit 20 becomes "0", that is, when the countdown ends, the control circuit 40 outputs a latch signal from the output terminal 47 to the control terminal of the cumulative value latch unit 15. When the cumulative value latch unit 15 receives the latch signal at its control terminal, it latches the adjusted cumulative value Z input from the adder 14 and outputs the signal Z N That is, the signal Z N corresponds to a point on the approximate line (3), and is therefore a corrected digital signal according to the analog signal X output by the sensor 1.

[0028] The above process is a new primary correction using the adjustment value of the count value and the adjustment value of the offset value corresponding to the temperature range of the cumulative value Y of the sensor device 100. N is output as highly accurate digital data that has been corrected for nonlinear characteristics.

[0029] As described above, the ΔΣ AD conversion circuit and sensor device of this embodiment are provided with an adjustment value storage unit 30 that stores an adjustment value for the count value and an adjustment value for the offset value, and are configured to adjust the count value and the offset value when the count value of the counting unit reaches a predetermined value.This makes it possible to provide a ΔΣ AD converter and sensor device that does not require a multiplication circuit, has a small circuit scale, and is highly accurate.

[0030] In this embodiment, the count value and the offset value are adjusted when the count value C reaches a predetermined value M, but this may be performed multiple times. Mis near the threshold value of the cumulative adjustment value Z, it is effective because it allows for coarse adjustment and fine adjustment.

[0031] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the present invention.

[0032] 1 sensor 10 Count value storage section 11 Offset value storage section 12 ΔΣAD modulator 13 Accumulator 14, 17, 18 adder 15 Accumulation value latch section 16 Multiplexer 20 Counting section 30 Adjustment value storage section 40 Control circuit 100 Sensor Device

[0033] Furthermore, although the adjusted cumulative value Z is input to the input terminal 43 of the control circuit 40, if the broken line approximation is performed only once, the signal Y may be input instead. It goes without saying that when no adjustment is required in the new primary correction, the adjusted count value and the adjusted offset value are set to "0". [Explanation of symbols]

[0034] 1 sensor 10 Count value storage section 11 Offset value storage section 12 ΔΣAD modulator 13 Accumulator 14, 17, 18 adder 15 Accumulation value latch section 16 Multiplexer 20 Coefficient part 30 Adjustment value storage section 40 Control circuit 100 Sensor Device

Claims

1. A ΔΣ AD converter that converts an input analog signal into a digital signal, a ΔΣ AD modulator that receives the analog signal and outputs a modulated signal; an accumulator that accumulates the modulated signals and outputs an accumulated value; a counting unit that counts a set count value; an adjustment value storage unit in which adjustment values ​​of the count value and adjustment values ​​of the offset value are stored; a first adder that outputs an adjusted cumulative value obtained by adding the cumulative value and an adjustment value of the offset value; a cumulative value latch unit to which the adjusted cumulative value is input; a control circuit that receives the adjusted cumulative value, the count value from the counter, and a threshold value of the adjusted cumulative value that determines a temperature range from the adjustment value storage unit, and outputs a control signal to the counter and a latch signal to the cumulative value latch unit; Equipped with the control circuit determines the temperature range in accordance with the adjusted cumulative value input from the first adder when the count value input from the counting unit reaches a predetermined value, and outputs a signal specifying the temperature range to the adjusted value storage unit; an adjustment value storage unit outputs an adjustment value of the offset value and an adjustment value of the count value according to the specified temperature range to the first adder and the counting unit; The control circuit outputs the latch signal to the cumulative value latch unit upon receipt of the completion of counting by the counting unit. A ΔΣ AD converter characterized by:

2. The adjustment value storage unit outputs an adjustment value of the count value to be added to the predetermined value to calculate an adjustment count value.

2. The ΔΣ AD converter according to claim 1, wherein:

3. The counter further includes a second adder that outputs an adjusted count value obtained by adding the count value of the counter unit and an adjustment value of the count value to the counter unit.

2. The ΔΣ AD converter according to claim 1, wherein:

4. a count value storage unit for storing an initial value of the count value to be set in the counting unit; a multiplexer that selects the adjusted count value and the initial value of the count value and outputs the selected value to the counting unit; The control circuit outputs a control signal to the multiplexer for selecting the adjusted count value or the initial value of the count value, and outputs a control signal to the counting unit for loading the count value output by the multiplexer or counting a set count value.

4. The ΔΣ AD converter according to claim 3.

5. an offset value storage unit in which an initial value of the offset value is stored; a third adder that outputs an adjusted offset value obtained by adding the adjusted value of the offset value and the initial value of the offset value, The first adder outputs the adjusted cumulative value obtained by adding the cumulative value and the adjusted offset value.

5. The ΔΣ AD converter according to claim 1, wherein:

6. a sensor element that outputs an analog signal corresponding to the measured physical information; a ΔΣ AD converter according to any one of claims 1 to 3, to which the analog signal is input; A sensor device comprising:

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