JP2009236603A - Temperature sensor, manufacturing method of temperature sensor, electrophoretic device, and electronic device - Google Patents

Abstract

A temperature sensor capable of accurately detecting a temperature with a circuit configuration having a relatively small mounting area, and a manufacturing method thereof.
An oscillation circuit (10), a power supply circuit (11) for supplying a predetermined power supply voltage to the oscillation circuit, and a temperature specifying circuit (20, 30) for specifying a temperature based on an oscillation frequency of the oscillation circuit are provided. The oscillation circuit (10) is configured such that the oscillation frequency increases in response to a rise in temperature, and the power supply circuit (11) is a power supply for causing the oscillation circuit to oscillate at a predetermined reference frequency at a predetermined reference temperature. The temperature specifying circuit (20, 30) is configured to supply a voltage, and is configured to specify the temperature based on the relationship information between the oscillation frequency of the oscillation circuit and the temperature.
[Selection] Figure 1

Description

  The present invention relates to a temperature sensor, and more particularly to a temperature sensor that has a simple configuration suitable for an electrophoresis apparatus incorporated in a wristwatch or the like and can be manufactured at a low cost, and a manufacturing method thereof.

  An electrophoretic device is a device that displays an image by controlling the voltage applied between electrodes to change the color tone of the appearance by controlling the movement of charged particles. The movement of the charged particles in this electrophoresis apparatus is affected by the viscosity of the solvent, and the viscosity of the solvent is highly temperature dependent. Therefore, it is necessary to drive with an optimum driving voltage and driving waveform according to the temperature. For example, JP 2005-527001 A discloses an invention in which a medium temperature is measured by a temperature searcher and a potential difference between electrodes of an electrophoretic element is controlled according to the measured temperature (see Patent Document 1).

In recent years, application examples in which an electrophoresis device is incorporated in a small-sized and portable device such as a wristwatch have been researched and developed.
JP 2005-527001 A

  In order to measure the temperature, it is necessary to connect an external component such as a reference resistor that defines the oscillation frequency and a thermistor that detects the temperature to the integrated oscillation circuit. However, if an external component is required, a mounting area for a circuit including an integrated circuit becomes large, and it becomes difficult to reduce the cost.

  In particular, when a temperature sensor is incorporated in a relatively small device such as a wristwatch, there is a strict requirement that even a single chip resistor should be reduced, and it is not desired to use an external resistor only for temperature measurement.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a temperature sensor capable of accurately detecting a temperature with a circuit configuration having a relatively small mounting area, and a method of manufacturing the same. There is.

  In order to solve the above problems, a temperature sensor of the present invention includes an oscillation circuit, a power supply circuit that supplies a predetermined power supply voltage to the oscillation circuit, a temperature identification circuit that identifies a temperature based on the oscillation frequency of the oscillation circuit, and . The oscillation circuit is configured such that the oscillation frequency increases in response to an increase in temperature. The power supply circuit is configured to supply a power supply voltage for causing the oscillation circuit to oscillate at a predetermined reference frequency at a predetermined reference temperature. The temperature specifying circuit is configured to specify the temperature based on the relationship information between the oscillation frequency of the oscillation circuit and the temperature.

  According to such a configuration, the oscillation circuit has a positive temperature characteristic in which the oscillation frequency increases as the temperature rises, and the power supply circuit has a power supply voltage such that the oscillation frequency has a positive temperature characteristic. Since the temperature specifying circuit refers to the relationship information between the oscillation frequency and temperature, if the oscillation frequency varies with temperature change, the temperature corresponding to the oscillation frequency is specified. be able to. Here, even if the elements constituting the oscillation circuit vary in the manufacturing process, all the oscillation circuits are adjusted to oscillate at the reference frequency at the reference temperature. Measurement error can be grasped in advance. In addition, since the correspondence relationship between the measurement target temperature range and the maximum measurement error is clear, the measurement target temperature range can be reversely set based on the allowable error range.

  Here, it is preferable that the power supply circuit sets the power supply voltage applied to the oscillation circuit within a temperature characteristic range in which the oscillation frequency increases as the temperature increases. In the oscillation circuit, when the temperature characteristic of the threshold value of the elements constituting the oscillation circuit is relatively large, a positive temperature characteristic that the frequency increases as the temperature rises appears in the oscillation frequency. On the other hand, if the influence of the temperature characteristic on the mobility of the elements constituting the oscillation circuit is relatively large, a negative temperature characteristic appears that the frequency decreases with increasing temperature. The temperature characteristic of the oscillation frequency of the entire oscillation circuit is determined depending on which temperature characteristic greatly affects. The lower the power supply voltage, the greater the influence of the threshold temperature characteristic, and the higher the power supply voltage, the greater the influence of the mobility temperature characteristic. Therefore, the temperature characteristic of the oscillation frequency of the oscillation circuit can be adjusted by adjusting the power supply voltage applied to the oscillation circuit. According to such a configuration, since the power supply voltage applied to the oscillation circuit is controlled in a range in which the oscillation frequency exhibits a positive temperature characteristic, the temperature can be measured based on the oscillation frequency of the oscillation circuit. Become.

  Here, the “oscillation circuit” may be a circuit having a positive temperature characteristic in which the oscillation frequency increases as the temperature rises, and the configuration is not limited. For example, the present invention can be applied to any circuit configuration in which a change in the threshold value of a transistor affects the oscillation frequency. For example, a rectangular wave oscillation circuit using hysteresis characteristics, an unstable multivibrator, and the like are included.

  For example, the oscillation circuit is a ring oscillator including an inverter. In this case, the inverter is configured by connecting in series a first transistor having a first polarity between a power supply voltage and a ground potential and a second transistor having a second polarity opposite to the first polarity. ing. The power supply circuit sets the power supply voltage applied to the ring oscillator higher than the threshold voltage of the first transistor and the second transistor.

  According to such a configuration, the threshold values of the first transistor and the second transistor vary with changes in temperature. If an odd number of inverters are connected in series and the output is fed back, the inverter oscillates at a frequency determined by the on-resistance of the transistor and the set capacitance or parasitic capacitance. The oscillation frequency of the ring oscillator also has a temperature characteristic due to the influence of the temperature characteristic of the threshold value or mobility of the transistor. An oscillation circuit having a positive temperature characteristic can be obtained by setting a power supply voltage that greatly affects the temperature characteristic of the threshold value of the transistor.

  Preferably, the power supply circuit stores a power supply voltage for oscillating at a reference frequency at a reference temperature for each sample of the oscillation circuit having various threshold values within an allowable range. . Further, a selection unit for setting which sample the oscillation circuit belongs to is provided. The power supply circuit supplies the power supply voltage stored for the sample corresponding to the setting of the selection unit to the oscillation circuit.

  According to this configuration, the power supply voltage for oscillating at the reference frequency at the reference temperature is stored in association with each of the plurality of types of samples. Therefore, if the power supply voltage for the sample corresponding to the mounted oscillation circuit is selected by the selection unit for each production lot or single unit, the oscillation circuit is adjusted so that it oscillates at the reference frequency at the reference temperature in the manufactured product. It becomes possible. Therefore, the configuration of the present invention is such that the specification of the power supply voltage by the calibration process for the sample and the setting of the power supply voltage for each of the manufactured products by selecting an approximate sample are performed separately (second method described later). Suitable for calibration method).

  For example, the temperature specifying circuit includes a counter and a count value temperature conversion circuit that converts the count value of the counter into temperature information. The counter receives a reference signal having a frequency higher than the oscillation frequency of the oscillation circuit, and outputs the number of periods of the reference signal that falls within a certain period of the oscillation signal from the oscillation circuit as a count value.

  According to this configuration, the oscillation frequency of the oscillation signal can be specified based on how many periods of the reference signal are included in one cycle of the oscillation signal, and the temperature corresponding to the specified oscillation frequency can be detected. .

  In addition, for example, the counter receives a reference signal having a frequency lower than the oscillation frequency of the oscillation circuit, and outputs the number of periods of the oscillation signal from the oscillation circuit that falls within a certain period of the reference signal as a count value. It may be configured.

  According to this configuration, the oscillation frequency of the oscillation signal can be specified based on how many oscillation signals are included in one cycle of the reference signal, and the temperature corresponding to the specified oscillation frequency can be detected. .

  An electrophoretic device according to the present invention includes an electrophoretic element, a driving waveform control circuit that changes a driving waveform based on the temperature specified by the temperature sensor of the present invention, and a driving circuit that drives the electrophoretic element with the driving waveform. And comprising.

  According to such a configuration, driving of the electrophoretic element can be controlled using a temperature sensor having a small mounting area, which is suitable for an electrophoretic device mounted on a small portable device such as a wristwatch.

Moreover, this invention is also an electronic device provided with the said temperature sensor.
According to such a configuration, the mounting area of the temperature sensor can be made relatively small, and the manufacturing cost can be made relatively low. The “electronic device” is, for example, an apparatus including an electrophoresis apparatus as a display device, and includes a wristwatch, an electronic book, electronic paper, and the like.

A manufacturing method of a temperature sensor of the present invention is a manufacturing method of a temperature sensor provided with an oscillation circuit,
The oscillation circuit increases the oscillation frequency as the temperature rises.
1) measuring a lower limit voltage at which oscillation stops for each of the oscillation circuit samples having various threshold values within an allowable range;
2) identifying a sample having the highest lower limit voltage as a reference sample;
3) identifying as a reference voltage a voltage at which all samples can oscillate based on the measured lower limit voltage;
4) specifying an oscillation frequency as a reference frequency when a reference voltage is applied to a reference sample at a predetermined reference temperature;
5) setting a power supply voltage for oscillating at the reference frequency at the reference temperature for the oscillation circuit to be adjusted;
It is provided with.

  When using the positive temperature characteristic of an oscillation circuit whose oscillation frequency increases as the temperature rises, the positive temperature characteristic becomes more prominent as the power supply voltage is closer to the threshold value of the elements constituting the oscillation circuit. The error of the oscillation frequency tends to decrease. Therefore, it is preferable to supply a power supply voltage as close as possible to the threshold voltage within a range in which oscillation does not stop. According to this method, the lower limit voltage at which the oscillation stops is measured for the sample representing the variation of the oscillation circuit that can be manufactured in step 1), and the sample having the highest lower limit voltage is determined as the reference limit in step 2). Extracted as a sample. In other words, the reference sample is a sample that can stop oscillation at the highest voltage. In step 3), since the voltage at which the reference sample oscillates is determined as the reference voltage, the reference voltage that will definitely oscillate all the oscillation circuits that can be manufactured is determined. Further, in step 4), the reference frequency for the reference sample is determined, and in step 5), the power supply voltage is set so that the oscillation circuit to be adjusted oscillates at the reference frequency at the reference temperature. According to the present invention, the reference frequency at the reference temperature is determined based on the sample representing the variation, and the power supply voltage that oscillates at the reference frequency at the reference temperature is set for each of the oscillation circuits. Therefore, even if the manufactured oscillation circuit varies, the maximum measurement error corresponding to the measurement target temperature range can be grasped in advance. In addition, since the correspondence relationship between the measurement target temperature range and the maximum measurement error is clear, it is possible to reversely set the measurement target temperature range based on the allowable error range.

Two calibration methods are conceivable for setting the power supply voltage for the oscillation circuit to be adjusted (step 5).
In the first calibration method of the present invention, in the step 5) of setting the power supply voltage,
5-1) identifying a power supply voltage for causing an oscillation circuit to be adjusted to oscillate at a reference frequency at a reference temperature;
5-2) setting a power supply voltage for the specified oscillation circuit to be adjusted as a power supply voltage of the oscillation circuit;
Is provided.

  According to the first calibration method, the reference frequency at the reference temperature is determined using the sample, and the oscillation circuit to be adjusted, that is, each individual specific manufactured product, oscillates at the reference frequency at the reference temperature. Such a power supply voltage is adjusted and set. Therefore, it is possible to manufacture a temperature sensor that can oscillate at the reference frequency accurately at the reference temperature for each individual oscillation circuit and can accurately predict the maximum error range.

In the second calibration method of the present invention, in the step 5) of setting the power supply voltage,
5-1) identifying a power supply voltage for oscillating at a reference frequency at a reference temperature for a sample other than the reference sample;
5-2) selecting a sample having a threshold value corresponding to the oscillation circuit to be adjusted;
5-3) setting a power supply voltage specified for the selected sample as a power supply voltage for the oscillation circuit to be adjusted;
Is provided.

  According to the second calibration method, the reference frequency at the reference temperature is determined using the sample, and the power supply voltage that oscillates at the reference frequency at the reference temperature is adjusted and specified for each of the plurality of samples. . For each oscillation circuit to be adjusted, that is, for each individual manufactured product, a sample corresponding to the oscillation circuit is selected, and the power supply voltage adjusted for the selected sample is the power supply for the oscillation circuit. Set as voltage. According to such a method, the power supply voltage is obtained in advance based on the sample representing the variation in the manufactured product, and the power supply voltage may be set for each oscillation circuit by checking the correspondence with the sample. Therefore, the calibration process can be completed in a relatively short time, and a temperature sensor capable of accurately predicting the maximum error range can be manufactured.

  Here, the number of samples is not limited, but it is preferable to use a sample in which threshold characteristics are dispersed so as to cover a range of threshold variation in a manufactured product. In addition, the larger the number of samples, the higher the possibility of selecting a sample that has a threshold characteristic that matches or is more similar to the manufactured product. At a minimum, it is preferable to perform a calibration process on a limit sample that represents the maximum range of threshold variation in a manufactured product.

Here, in the step 3) of specifying the reference voltage, it is preferable to specify a voltage obtained by adding a predetermined margin to the highest lower limit voltage among the lower limit voltages indicated by the plurality of reference samples as the reference voltage.
Even if there are variations among the plurality of reference samples, the reference voltage is set based on the sample in which oscillation is most likely to stop, so that oscillation can be reliably performed regardless of variations.

Here, it is preferable that the step of specifying the reference frequency in 4) specifies the highest frequency among the oscillation frequencies indicated by the plurality of reference samples as the reference frequency.
Oscillation circuits other than the reference sample include those whose oscillation does not stop even with a power supply voltage lower than that of the reference sample. Such an oscillation circuit can increase the oscillation frequency by increasing the power supply voltage to be supplied. Therefore, if the highest oscillation frequency among the reference samples is set as the reference frequency, the power supply voltage for generating the reference frequency at the reference temperature can be set for all the oscillation circuits.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
As described above, the calibration method according to the present invention has two modes.
The two modes are common until the reference frequency at the reference temperature is specified based on the reference sample of the oscillation circuit.

The first calibration method is a method for individually adjusting and setting the power supply voltage for the oscillation circuit to be adjusted for each of the manufactured oscillation circuits.
The second calibration method specifies a power supply voltage for oscillating at a reference frequency at a reference temperature for samples other than the reference sample, and sets a threshold value corresponding to the oscillation circuit to be adjusted in the manufacturing process. This is a method of selecting a sample to be included and setting a power supply voltage specified for the selected sample as a power supply voltage for an oscillation circuit to be adjusted.

In the first calibration method, the power supply voltage is adjusted and set by calibration for all manufactured products. Therefore, all the oscillation circuits are oscillated at the reference frequency accurately at the reference frequency, and the maximum theoretically expected. It is possible to oscillate within the error range. On the other hand, in the second calibration method, the power supply voltage is adjusted and set by performing calibration processing only for a limited number of samples, so that the number of man-hours for manufacturing is relatively reduced with a certain degree of accuracy. be able to.
Hereinafter, the first calibration method is exemplified in the first embodiment, and the second calibration method is exemplified in the second embodiment.

(Embodiment 1)
In the first embodiment of the present invention, based on the first calibration method, a reference frequency at a reference temperature is obtained based on a sample of a ring oscillator that is an oscillation circuit, and a reference frequency is obtained for each of the manufactured ring oscillators. The present invention relates to a temperature sensor adjusted to supply a power supply voltage for oscillating at a reference frequency at a temperature.

FIG. 1 shows a block diagram of a temperature sensor 1 according to the first embodiment.
As shown in FIG. 1, the temperature sensor 1 includes a ring oscillator 10, a power supply circuit 11, a counter 20, a reference signal oscillator 21, a count value temperature conversion circuit 30, and a count value temperature relation information storage unit 31. The ring oscillator 10 corresponds to the oscillation circuit of the present invention, and the counter 20 and the count value temperature conversion circuit 30 correspond to the temperature specifying circuit of the present invention.

  The ring oscillator 10 is an example of an oscillation circuit having a positive temperature characteristic such that the oscillation frequency increases in response to a rise in temperature. As an oscillation circuit having a positive temperature characteristic, a rectangular wave oscillation circuit using a hysteresis, an unstable multivibrator, or the like can be used in addition to a ring oscillator.

FIG. 2 shows a block diagram of the ring oscillator 10.
As shown in FIG. 2, the ring oscillator 10 is configured by connecting a plurality of inverters INV in series. The output of the final stage inverter INV is connected to the input terminal of the first stage inverter INV. In order to operate as an oscillator, positive feedback is required, so the number of inverters in series is usually an odd number.

  As shown in the lower part of FIG. 2, each inverter INV includes a P-type (first polarity) first transistor Tr1 and an N-type (second polarity) second transistor Tr2 with a power supply voltage Vdc and a ground potential. Are connected in series. The power supply voltage Vdc is set higher than the threshold voltage Vth1 of the first transistor Tr1 and the threshold voltage Vth2 of the second transistor Tr2. The gate of the first transistor Tr1 and the gate of the second transistor Tr2 are directly connected to form an input terminal Vin of the inverter. One of the source / drain of the first transistor Tr1 and one of the source / drain of the second transistor Tr2 Are connected to form an output terminal Vout. A capacitor C having a predetermined capacitance (for example, 10 pF) is connected to the output terminal Vout.

  According to the above configuration, a signal having a polarity opposite to that connected to the input terminal Vin is output to the output terminal Vout. When the first transistor Tr1 is turned on (the second transistor Tr2 is turned off), the capacitor C is charged with a time constant determined by the on-resistance of the first transistor Tr1 and the capacitor C, and the output voltage of the output terminal Vout Changes. When the second transistor Tr2 is turned on (the first transistor Tr1 is turned off), the charge of the capacitor C is discharged with a time constant determined by the on-resistance of the second transistor Tr2 and the capacitor C, and the output voltage of the output terminal Vout Changes. That is, the output voltage of the output terminal Vout changes with a delay of the change of the pulse signal with respect to the input terminal Vin. An odd number of such inverters INV are connected in series and the output is fed back to the input side to oscillate at an oscillation frequency corresponding to the time constant.

  FIG. 3 shows the relationship between temperature and oscillation frequency (temperature characteristics) according to the power supply voltage applied to the ring oscillator. FIG. 3A shows a case where the temperature characteristic of the threshold value of the transistor has a relatively large influence, and FIG. 3B shows a balance between the temperature characteristic of the threshold value of the transistor and the temperature characteristic of the mobility. FIG. 3C shows a case where the temperature characteristics of the transistor mobility are relatively greatly affected.

  It is known that the oscillation frequency f of the ring oscillator 10 is affected by both the temperature characteristic of the threshold voltage Vth of the transistor constituting the inverter INV and the temperature characteristic of the mobility of the transistor. For example, in the region where the power supply voltage applied to the inverter is close to the threshold voltage Vth of the transistor, the influence of the temperature characteristic of the threshold value of the transistor on the oscillation frequency of the ring oscillator becomes relatively large. On the other hand, when the power supply voltage applied to the inverter is much higher than the threshold voltage Vth of the transistor, the influence of the temperature characteristics of the transistor mobility on the oscillation frequency of the ring oscillator becomes relatively large.

  The threshold voltage tends to decrease with increasing temperature. When the threshold value is lowered, the switching timing of the transistor is advanced, and the cycle of the oscillation frequency determined by repeated switching is shortened. Therefore, it is considered that the oscillation frequency increases as the temperature increases. On the other hand, the mobility is proportional to about −2.2 to the absolute temperature in the case of P-type silicon and about −2.42 to the absolute temperature in the case of N-type silicon, and decreases with increasing temperature. The magnitude of mobility is the carrier velocity in the semiconductor and corresponds to the speed of state transition of the transistor. Therefore, the oscillation frequency decreases as the temperature rises. When the power supply voltage applied to the inverter becomes relatively low, the influence of the threshold becomes strong, and when the power supply voltage becomes relatively high, the influence of the mobility becomes strong.

  Therefore, as shown in FIG. 3A, in a region where the power supply voltage applied to the inverter is relatively close to the threshold voltage Vth of the transistor and the temperature characteristic of the threshold voltage Vth of the transistor is dominant, the ring The oscillation frequency f of the oscillator shows a tendency to increase with an increase in temperature t.

  On the other hand, as shown in FIG. 3C, in the region where the power supply voltage applied to the inverter is much higher than the threshold voltage Vth of the transistor and the temperature characteristics of the transistor mobility are dominant, the oscillation of the ring oscillator is performed. The frequency f shows a tendency to decrease as the temperature t increases.

  Further, as shown in FIG. 3B, when the power supply voltage is applied so that the temperature characteristic of the threshold voltage of the transistor and the temperature characteristic of the mobility have the same influence, both influences are balanced, It is also possible to reduce the influence of temperature on the oscillation frequency of the oscillator.

  As shown in FIG. 3A, the temperature sensor of the present embodiment actively uses the tendency that the oscillation frequency increases in response to the temperature increase in the region where the oscillation frequency of the oscillator shows a positive temperature characteristic. And configured to detect the temperature.

  In order to operate the ring oscillator 10 with a positive temperature characteristic as shown in FIG. 3A, the power supply circuit 11 of the temperature sensor 1 shown in FIG. 1 makes the ring oscillator 10 have a positive temperature characteristic. The power supply voltage Vdc for operating is generated and supplied. The power supply circuit 11 only needs to have a general circuit configuration as a stabilized power supply, but in order to be able to set a strict power supply voltage, a DC-DC capable of continuously changing the output voltage. It is preferable to have a circuit configuration as a converter.

  In particular, in this embodiment, the power supply circuit 11 is a power supply adjusted so that the ring oscillator 10 oscillates at a predetermined reference frequency fref at a predetermined reference temperature tref, regardless of the characteristics of the transistor. The voltage Vdc is supplied. A method for adjusting the power supply voltage Vdc will be described later.

  The counter 20 refers to the reference signal Sref generated by the reference signal oscillator 21 and counts the oscillation frequency of the oscillation signal from the ring oscillator 10. There are two methods for counting the oscillation frequency, which will be described with reference to FIG.

  FIG. 4A shows the first counting method. The first counting method is applied when the reference signal Sosc generated by the reference signal oscillator 21 is set to have a frequency higher than the oscillation frequency fosc of the ring oscillator 10. The counter 20 outputs, as a count value, the number of periods Tref of the reference signal Sref that falls within a certain period Tosc of the oscillation signal Sosc from the ring oscillator 10.

  FIG. 4B shows a second counting method. The second counting method is applied when the reference signal Sref generated by the reference signal oscillator 21 is set to have a frequency lower than the oscillation frequency fosc of the ring oscillator 10. The counter 20 outputs, as a count value, the number of periods Tosc of the oscillation signal Sosc from the ring oscillator 10 that falls within a certain period Tref of the reference signal Sref of the reference signal Sref.

  Whichever counting method is employed, the frequency Fref and / or the period Tref of the reference signal Sref is known, so that the frequency of the oscillation signal Sosc can be easily calculated according to the count value of the counter 20. . In the first counting method (FIG. 4A), the frequency fosc (= Fref / n) of the oscillation signal Socs can be calculated by dividing the frequency Fref of the reference signal Sref by the count value n. In the second counting method (FIG. 4B), the frequency fosc (= Fref * n) of the oscillation signal Socs can be calculated by multiplying the frequency Fref of the reference signal Sref by the count value n.

  The count value temperature conversion circuit 30 is a block that specifies the temperature based on the calculated oscillation frequency focs of the ring oscillator 10. The count value temperature conversion circuit 30 calculates the temperature corresponding to the oscillation frequency focs with reference to the count value temperature relation information stored in the count value temperature relation information storage unit 31 and outputs the calculated temperature to the display 40. Yes.

FIG. 5 illustrates an oscillation frequency (count value) -temperature characteristic (relation information).
The count value temperature-related information is information that prescribes characteristics as shown by characteristics f1 to f3 in FIG. 5, for example. The differences in the slopes of the characteristics f1 to f3 are caused by variations in the transistors constituting the ring oscillator 10. The count value temperature relationship information storage unit 31 stores the relationship between the oscillation frequency focs and the corresponding temperature t as shown in FIG. 5 in the form of a relational expression or a relation table.

  In particular, in the present invention, even if the count value temperature relation information stored in the count value temperature relation information storage unit 31 is any characteristic as represented by the characteristics f1 to f3, the reference frequency at the predetermined reference temperature tref. It is characterized in that it is relation information that fref corresponds to. In other words, the power supply circuit 11 supplies the ring oscillator 10 with the power supply voltage Vdc so that the oscillation frequency fosc is always the reference frequency fref at the reference temperature tref regardless of the characteristics of the transistor. It has been adjusted. The significance of the adjustment of the present invention (also referred to as “calibration”) becomes clear compared to the case where such adjustment is not performed.

FIG. 6 shows oscillation frequency-temperature characteristics when the calibration of the present invention is not performed.
It is well known that the threshold voltage of a transistor varies to some extent during the manufacturing process. If the threshold voltage of the transistor varies, the oscillation frequency-temperature characteristic of the ring oscillator determined according to the threshold voltage naturally varies.

  Here, the slope of the oscillation frequency-temperature characteristic is based on the variation of the threshold voltage of the transistor, whereas the intercept of each characteristic varies depending on the power supply voltage Vdc. If the power supply voltage Vdc is not adjusted according to the threshold voltage of the transistor, it is considered that the oscillation frequency-temperature characteristics vary as indicated by f1 to f3 in FIG. In this case, the oscillation frequency-temperature characteristic for a ring oscillator configured with a transistor having a specific threshold voltage characteristic is used for a ring oscillator configured with a transistor having another threshold voltage characteristic. The error is too large to be used.

  In FIG. 6, if the measurement target temperature range TR is the range shown in the figure, the maximum error of the measured temperature is large as shown by Δtx due to transistor variations. If the variation in the oscillation frequency-temperature characteristics is not adjusted, it cannot be determined how much error is included in the detected temperature. This makes it impossible to use in an application device that uses a measurement result based on whether or not the maximum error is within an allowable range.

  Therefore, in the first embodiment, based on the first calibration method, the reference frequency at the reference temperature is specified based on the limit sample of the ring oscillator (oscillation circuit), and the ring oscillation to be adjusted in the manufacturing process is specified. For the oscillator (manufactured product), the power supply voltage for oscillating at the reference frequency at the reference temperature is specified and set individually. That is, regardless of how the threshold characteristics of the transistors vary, the ring oscillator power supply voltage Vdc is individually and specifically set so that the oscillation frequency-temperature characteristics of the ring oscillator always pass a predetermined reference point. It is characterized by adjusting.

FIG. 5 shows the oscillation frequency-temperature characteristics when calibrated according to the present invention.
As shown in FIG. 5, the slopes of the oscillation frequency-temperature characteristics f1 to f3 are variations in the threshold voltage of the transistors that are unavoidable in manufacturing. However, any oscillation frequency-temperature characteristic f1-f3 is adjusted so that it always passes through the reference point Pref, that is, oscillates at a predetermined frequency (reference frequency fref) at a predetermined temperature (reference temperature tref). Has been. Therefore, the frequency detection error at the reference temperature tref is zero, and the maximum error range determined by the deviation is linearly determined as the distance from the reference temperature tref is increased. Assuming that the characteristics f1 and f3 correspond to the maximum variation of the threshold voltage, in FIG. 5, the maximum error range in the measurement target temperature range TR can be obtained as Δt. By appropriately selecting the reference temperature tref and the measurement target temperature range TR, it is possible to measure the temperature within the range of the obvious maximum error. This adjustment is realized by adjusting the power supply voltage dc of the ring oscillator 10, that is, by translating the oscillation frequency-temperature characteristics f1-f3.

  Specifically, in this embodiment, variations in threshold voltages of transistors are grouped according to types of marginal samples (marginal samples: levels) that define a maximum range in which characteristics vary in manufacturing. Then, the reference frequency fref at the reference temperature tref is determined based on the limit sample having the worst condition among the plurality of limit samples. In particular, in the first calibration method described in the first embodiment, the power supply voltage Vdc is individually set so that the actual manufactured product oscillates at the reference frequency fref at the reference temperature tref.

(Manufacturing method of this embodiment)
Next, the calibration method of this embodiment will be described based on the flowchart of FIG. As described above, the present embodiment corresponds to the first calibration method. The following steps S100 to S103 are steps common to both the first calibration method and the second calibration method, and steps S104 and S105 are steps specialized for the first calibration method. .
(Step S100)
First, the lower limit voltage at which the oscillation stops is measured for each of the limit samples of the ring oscillator having various threshold values within an allowable range.

  In FIG. 8, the maximum range of variation that can occur in the manufacturing process is indicated by hatching in the first (P-type) transistor Tr1 and the second (N-type) transistor Tr2 constituting the inverter included in the ring oscillator. A sample with the highest threshold Vth1 for the first transistor Tr1 is represented by “PH”, and a sample with the lowest threshold Vth1 is represented by “PL”. A sample with the highest threshold Vth2 for the second transistor Tr1 is represented by “NH”, and a sample with the lowest threshold Vth2 is represented by “NL”.

  The limit sample refers to a sample that represents the maximum range of manufacturing variation. In FIG. 8, samples corresponding to five points obtained by adding the center point P0 to the four points P1 to P4 forming the vertices of the maximum variation range are used as limit samples. The limit sample PH-NH is a sample corresponding to the point P1 at which the threshold voltages of the first transistor Tr1 and the second transistor Tr2 are both the highest. The limit sample PH-NL is a sample corresponding to the point P2 where the first transistor Tr1 has the highest threshold voltage and the second transistor Tr2 has the lowest threshold voltage. The limit sample PL-NH is a sample corresponding to the point P3 where the first transistor Tr1 has the lowest threshold voltage and the second transistor Tr2 has the highest threshold voltage. The limit sample PL-NL is a sample corresponding to the point P4 at which the threshold voltages of the first transistor Tr1 and the second transistor Tr2 are both the lowest. The limit sample PT-NT is a sample corresponding to the point P0 where the threshold voltages of the first transistor Tr1 and the second transistor Tr2 are both average values. A sample with the worst oscillation condition is included in any of these five points. Therefore, the lower limit voltage at which the oscillation stops when the power supply voltage is lowered at each of these five points is measured. Since even one limit sample varies, it is preferable to prepare and measure a plurality of chips for each limit sample.

FIG. 9 shows the lower limit voltage measured for each of the limit samples.
In FIG. 9, the chip number is a serial number of a chip prepared for each limit sample. The transistor size is a serial number obtained by variously changing the transistor size, that is, the channel length and the channel width, in the limit samples having the same threshold voltage. As shown in FIG. 9, the lower limit voltage at which oscillation stops slightly varies depending on the chip and transistor size, but if the limit sample is the same, that is, if the threshold voltage setting of the transistor is almost the same setting It can be seen that the same lower limit voltage is shown.

(Step S101)
As the next step, the limit sample with the highest lower limit voltage is identified as the reference limit sample.

  The temperature characteristic of the threshold voltage of the transistor is more strongly affected as the power supply voltage is lowered. However, if the power supply voltage is lowered too much, the oscillation itself stops. Therefore, the limit sample at which oscillation stops at the highest voltage is specified as a sample with severe oscillation conditions.

  In FIG. 9, the group with the highest oscillation lower limit voltage is a limit sample of PL-NH. Therefore, this limit sample is specified as the reference limit sample for determining the reference voltage.

(Step S102)
As a next step, a voltage at which all limit samples can oscillate based on the determined lower limit voltage is specified as a reference voltage.
In particular, here, a voltage obtained by adding a predetermined margin to the highest lower limit voltage among the lower limit voltages indicated by the plurality of reference limit samples is specified as the reference voltage. By using a voltage higher than any of the numerical values of the reference limit sample with the strictest oscillation conditions as a reference voltage, any ring oscillator can be reliably oscillated.

  In FIG. 9, the lower limit voltage varies around 0.880 V in the limit sample (reference limit sample) of PL-NH. Therefore, here, 0.900V is set as the reference voltage with a margin of about 0.120V.

(Step S103)
As a next step, an oscillation frequency when a reference voltage is applied to a reference limit sample at a predetermined reference temperature is specified as a reference frequency. Here, when assuming the ring oscillator used for a normal small portable apparatus, since the center temperature of the temperature range to be used is about room temperature normally, 25 degreeC is assumed here as predetermined | prescribed reference temperature.

  In particular, here, the highest frequency among the oscillation frequencies indicated by the plurality of reference limit samples is specified as the reference frequency. Samples with low frequency can be adjusted to the reference frequency by increasing the power supply voltage, so if the highest frequency among multiple reference limit samples is used as the reference frequency, any sample can be used. It is possible to adjust to the reference frequency without stopping oscillation.

  FIG. 10 shows the oscillation frequency when a reference voltage of 0.900 V determined in step S102 is applied and arranged at a reference temperature for a plurality of chips of the limit sample of the reference limit sample PL-NH. In FIG. 10, the highest oscillation frequency is 5.201 kHz of chip number 5. Therefore, this frequency is determined as the reference frequency.

  Since an appropriate reference frequency at the reference temperature is determined by the above steps, the reference frequency at the reference temperature is determined for each manufactured ring oscillator by the following steps specialized for the first calibration method. Adjust the power supply voltage to oscillate.

(Step S104)
As the next step, the power supply voltage for oscillating at the reference frequency at the reference temperature is specified for the actually manufactured ring oscillator. This process is the central process of the first calibration. That is, for each manufactured ring oscillator, the oscillation frequency is measured while changing the power supply voltage at the reference temperature, and the power supply voltage Vdc when the oscillation frequency becomes the reference frequency (= 5.201 kHz) is specified. Go.

  This process is a process of adjusting the characteristics f1 to f3 whose slopes vary for each limit sample as shown in FIG. 6 so as to pass through the reference point Pref as shown in FIG. This is a process of correctly specifying and recording each power supply voltage Vdc. The power supply voltage Vdc specified for each manufactured product is recorded so that it can be set in the power supply circuit 11 of the temperature sensor to be manufactured.

(Step S105)
As the last step, the power supply voltage for the manufactured product subjected to the calibration process is set in the power supply circuit 11. That is, in the temperature sensor including the ring oscillator to be adjusted, the power supply voltage Vdc specified and recorded for each ring oscillator is set in the power supply circuit 11.

  FIG. 11 shows an example of a product with the most variation in threshold characteristics, taking a limit sample as an example, and measuring the change in oscillation frequency when the temperature is changed for each limit sample after completion of the calibration. It is a thing. As shown in FIG. 11, any limit sample (manufactured product) is adjusted to oscillate at the reference frequency fref = 5.201 kHz at 25 ° C. which is the reference temperature tref. The slope specified based on the above measurement is different for each limit sample.

  If this slope and the passing point Pref (reference frequency fref at the reference temperature tref) are determined, the oscillation frequency-temperature characteristics for each limit sample (manufactured product) can be specified. Therefore, in the count value temperature relationship information storage unit 31, the oscillation frequency-temperature characteristic according to the type of limit sample mounted on the ring oscillator 10 specified as a result of the measurement of FIG. 11 (see FIG. 5). Are stored in the form of a relational expression or a relation table.

In the temperature sensor manufactured through the above calibration, an oscillation frequency-temperature characteristic in which the ring oscillator 10 passes through the reference point Pref (reference frequency fref at the reference temperature tref) is set. Therefore, the temperature measured by the temperature sensor has a clearly defined maximum error range according to the measurement target temperature range TR as is apparent from FIG.
In addition, although it is preferable to automate the process of the said steps S100-105 with a computer apparatus, you may also require a part of manpower.

As described above, the first embodiment has the following advantages.
1) According to the temperature sensor 1 of the first embodiment, the power supply circuit 11 is adjusted so as to supply a power supply voltage whose oscillation frequency has a positive temperature characteristic to the oscillation circuit, and the count value temperature conversion circuit 30 Refers to the oscillation frequency-temperature characteristic corresponding to the threshold voltage characteristic of the transistor of the ring oscillator 10, so that even when the oscillation frequency fluctuates with temperature change, the temperature corresponding to the oscillation frequency is accurately measured. Is possible. In particular, the ring oscillator 10 is supplied with the power supply voltage Vdc calibrated so as to oscillate at the reference frequency fref at the reference temperature tref. Therefore, even if the transistors vary, the temperature range TR to be measured TR The maximum measurement error Δt corresponding to can be grasped in advance. Further, since the correspondence relationship between the measurement target temperature range TR and the maximum measurement error Δt is clear, the measurement target temperature range TR can be reversely set based on the allowable error range.

  2) According to the power supply circuit 11 of the first embodiment, the power supply voltage applied to the ring oscillator 10 is set in a range of positive temperature characteristics in which the oscillation frequency increases as the temperature rises. The temperature can be measured based on the oscillation frequency.

  3) The ring oscillator 10 of the first embodiment includes an inverter INV, and the inverter INV is configured by connecting a P-type first transistor Tr1 and an N-type second transistor Tr2 in series. It is possible to oscillate at a frequency corresponding to a time constant determined by the on-resistance and the set capacitance or parasitic capacitance.

  4) According to the manufacturing method of the first embodiment (steps S100 to S101), since the limit sample having the worst oscillation condition is specified and the reference voltage is set based on the limit sample, the power supply voltage is set within a range in which the oscillation does not stop. Is possible.

  5) According to the manufacturing method of the first embodiment (step S102), when there are a plurality of reference limit samples, the reference voltage is set based on the sample that hardly oscillates even if there are variations. Therefore, it is possible to reliably oscillate even if there is a variation in the limit sample.

  6) According to the manufacturing method of the first embodiment (step S103), since the highest oscillation frequency among the reference limit samples is set as the reference frequency, almost all manufactured products are generated at the reference frequency at the reference temperature. Therefore, it is possible to set the power supply voltage.

  7) According to the manufacturing method of the first embodiment (steps S104 and S105), based on the first calibration method, the power supply voltages of all manufactured products are calibrated so as to oscillate at the reference frequency at the reference voltage. Therefore, it is possible to provide a temperature sensor that does not deviate from the predicted maximum error. In addition, it is possible to accurately associate the measurement target temperature range TR with the maximum error amount.

(Second Embodiment)
In the first embodiment, the power supply circuit 11 is adjusted to output the power supply voltage Vdc calibrated for each temperature sensor, but the second embodiment of the present invention is based on the second calibration method. For samples other than the reference sample, the power supply voltage for oscillating at the reference frequency at the reference temperature is specified in advance. In the manufacturing process, a sample having a threshold value corresponding to the oscillation circuit to be adjusted is selected, and the power supply voltage specified for the selected sample is the power supply voltage for the oscillation circuit to be adjusted. Set individually.

FIG. 12 is a block diagram of the temperature sensor 1 according to the second embodiment.
As shown in FIG. 12, the temperature sensor 1b includes the ring oscillator 10, the counter 20, the reference signal oscillator 21, the count value temperature conversion circuit 30, and the count value temperature relation information storage unit 31, as described in the first embodiment. Is the same.

  The second embodiment includes a selection unit 12 and a power supply voltage storage unit 13, and the power supply circuit 11 b is configured to be able to output a power supply voltage Vdc corresponding to a set value of the selection unit 12. And different.

The selection unit 12 is configured to be able to set a plurality of setting values, and is a switch such as a DIP switch, for example. For example, as shown in FIG. 8, if it is configured to be set for five limit samples, the set value is “5”, and therefore a switch capable of setting at least 3 bits (= 8) is provided. The relationship between the setting value for the selection unit 12 and the limit sample is as shown in Table 1, for example.

  The power supply voltage storage unit 13 stores the power supply voltage Vdc specified by the manufacturing method of the first embodiment for each limit sample. That is, the power supply voltage Vdc for oscillating at the reference frequency at the reference temperature for the reference limit sample and other limit samples specified in the following step S106 is stored in association with the limit sample.

  The power supply circuit 11 b is configured to read the power supply voltage Vdc for the corresponding limit sample based on the set value of the selection unit 12 from the power supply voltage storage unit 13 and supply the power supply voltage Vdc to the ring oscillator 10. The power supply circuit 11b is preferably configured to be able to continuously change the output power supply voltage. It is necessary to change the power supply voltage by at least the number of limit samples to be set and to enable output.

  Note that the power supply voltage storage unit 13 stores the power supply voltage Vdc and the selection unit 12 can select a sample that is not limited to the limit sample, and the number of samples is limited to only five points of the limit sample. There is no need. Rather, it can be said that it is preferable to use as many samples as possible, which are dispersed in the range of variations in the threshold voltage of the transistors in the manufactured product. This is because the larger the number of samples, the higher the possibility of obtaining samples having the same or more similar threshold characteristics in the manufactured product. In the present embodiment, only five limit samples are used in order to enable calibration processing with a minimum number of samples.

(Manufacturing method of Embodiment 2)
Next, the calibration method of the second embodiment will be described based on the flowchart of FIG.
As described above, the present embodiment corresponds to the second calibration method of the present invention. Since the following steps S100 to S103 are common to the first calibration method described in the first embodiment, the description thereof is omitted. Steps S106 to S108 are steps specialized for the second calibration method.

  An appropriate reference frequency at the reference temperature is specified by the common steps S100 to S103.

(Step S106)
As a next step, a power supply voltage for oscillating at a reference frequency at a reference temperature is specified for limit samples other than the reference limit sample. In the first embodiment, the calibration performed for each manufactured oscillator is performed on the limit sample in the second embodiment.

  Therefore, for each sample other than the reference limit sample, the oscillation frequency is measured while changing the power supply voltage at the reference temperature, and the power supply voltage Vdc when the oscillation frequency becomes the reference frequency (= 5.201 kHz) is specified. To go. By this processing, the characteristics f1 to f3 whose slopes vary for each limit sample as shown in FIG. 6 are adjusted so that they always pass through the reference point Pref as shown in FIG. The power supply voltage Vdc specified for each limit sample is recorded in the power supply voltage storage unit 13 in association with the limit sample so that it can be set in the power supply circuit 11b of the temperature sensor to be manufactured.

(Step S107)
The next step is processing for each actually manufactured ring oscillator.
First, for each ring oscillator manufactured or for each production lot, determine which threshold voltage characteristic of the manufactured product is close to the threshold voltage characteristic of the limit sample. Select a limit sample with similar voltage characteristics. The fact that the threshold characteristics are close means that the power supply voltage required to oscillate the same reference frequency is also approximated.

(Step S108)
Therefore, as the next step, the selection unit 12 is operated so that the set value corresponds to the selected limit sample. By this processing, in the manufacturing process, the selection unit 12 sets the threshold voltage characteristics of the transistor of the ring oscillator 10 mounted on the temperature sensor 1b according to which limit sample shown in Table 1 is approximate. Value is set.
In addition, although it is preferable to automate the process of the said step S106-108 with a computer apparatus, you may also involve a part manually.

  The power supply circuit 11b reads the set value indicated by the selection unit 12, and determines which limit sample is supported based on the correspondence shown in Table 1. Then, the power supply voltage Vdc adjusted for the corresponding limit sample is read from the power supply voltage storage unit 13 and the power supply voltage Vdc is output to the ring oscillator 10. If the set value for the selection unit 12 is correct, the temperature characteristic of the oscillation frequency of the ring oscillator 10 should surely pass the reference point Pref (FIG. 5: reference frequency fref at the reference temperature tref).

  In the second embodiment, the selection unit 12 and the power supply voltage storage unit 13 are not essential components. The power supply circuit 11b may be configured to directly set the power supply voltage Vdc of the limit sample whose threshold characteristic approximates the manufactured product to be adjusted.

  As described above, according to the second embodiment, it is possible to set the power supply voltage Vdc that is adjusted to the oscillation frequency-temperature characteristics that pass through the reference point Pref for all limit samples. Therefore, the temperature sensor can be adjusted to oscillate at the reference frequency at the reference temperature by setting the power supply voltage Vdc adjusted for the limit sample whose threshold characteristics are most approximated in the manufactured product for each manufactured product. Become.

  In particular, according to the second embodiment, the calibration process that oscillates at the reference frequency at the reference temperature is performed only for a certain number of samples, and any one of the manufactured products is selected depending on the degree of approximation of the threshold characteristic. Since it is sufficient to select a sample, it is possible to relatively reduce the number of manufacturing steps while maintaining a certain measurement accuracy.

(Embodiment 3)
In Embodiment 3 of the present invention, an electrophoresis apparatus is exemplified as a device on which the temperature sensor described in the above embodiment is mounted.

FIG. 14 shows a block diagram of the electrophoresis apparatus of this embodiment.
As shown in FIG. 14, the electrophoresis apparatus includes an element substrate 100, a controller 300, a temperature sensor 1 (1 b), and a drive waveform control circuit 50.

  The element substrate 100 includes a display panel A, a scanning line driving circuit 130, a data line driving circuit 140, and a counter electrode modulation circuit 150. The display panel A includes a plurality of pixels 105, and these pixels 105 include a TFT 110 that is a switching element, a storage capacitor Cs, and an electrophoretic element 120 to which a voltage is supplied by the TFT 110. On the display panel A, a plurality of scanning lines 101 are formed in parallel along the X direction shown in the figure, and a plurality of data lines 102 are formed in parallel along the Y direction. Each pixel is arranged in a matrix corresponding to the intersection of the scanning line 101 and the data line 102.

  Although not shown, the controller 300 includes an image signal processing circuit and a timing generator. The image signal processing circuit generates image data and a counter electrode control signal, and inputs them to the data line driving circuit 140 and the counter electrode modulation circuit 150, respectively. The counter electrode modulation circuit 150 supplies a bias signal and a power supply voltage to the common electrode of the pixel and the counter electrode of the storage capacitor, respectively. For example, image reset is set by a positive or negative high level bias signal (reset signal). The reset signal is output for a predetermined period before the data driving circuit 140 outputs image data. The reset operation is used to initialize the spatial state by attracting the electrophoretic particles migrating in the dispersion medium in the electrophoretic element 120 to the pixel electrode or the common electrode. The timing generator generates various timing signals for controlling the scanning line driving circuit 130 and the data line driving circuit 140 when reset settings and image data are output from the image signal processing circuit.

  The temperature sensor 1 (1b) outputs environmental temperature information corresponding to the oscillation frequency of the ring oscillator 10 as described in the above embodiment. The drive waveform control circuit 50 is configured to be able to specify an appropriate drive waveform based on the environmental temperature information.

FIG. 15 shows the relationship between the temperature and the appropriate driving voltage in the electrophoretic element.
As shown in FIG. 15, the moving speed of the particles in the electrophoretic element has a strong correlation with the viscosity of the solvent in which the charged particles are dispersed, and generally the higher the temperature, the lower the viscosity of the solvent. A low viscosity means that the particles move easily, and means that the moving speed of the particles becomes high.

  The higher the moving speed of the charged particles, the better in terms of switching the display color, but if the moving speed of the charged particles is too high, an undesired phenomenon that the charged particles that have reached the counter electrode bounce will occur. Therefore, the moving speed of charged particles should be controlled within an appropriate range. The voltage shown in FIG. 15 is an appropriate drive voltage determined according to the environmental temperature.

  The drive waveform control circuit 50 stores the relation information between the environmental temperature and the appropriate drive voltage as shown in FIG. 15 in the form of a relation table or a relational expression, and sets the environmental temperature output from the temperature sensor 1 (1b). The reference drive waveform is modified (amplified or the like) so that the amplitude corresponds to the adapted drive voltage, and the modified drive waveform is applied to the scanning line drive circuit 130, the data line drive circuit 140, and the counter electrode modulation circuit 150. It comes to supply.

  In the above configuration, in the display panel A, when all the scanning line signals become active at the reset timing, all the data signals are set to the white or black level, and the reset signal is applied from the counter electrode modulation circuit 150 to the common electrode. Then, all the electrophoretic elements 120 are set to white or black display (in the case of binary display). Thereafter, the scanning lines 101 are sequentially selected, and writing to the image 105 is performed. When the TFT 110 of the specific pixel 105 is turned on, a data signal (image signal) is written from the data line driving circuit 140 to the pixel electrode of the electrophoretic element 120 in synchronization with the scanning line selection. At this time, the storage capacitor Cs is also charged at the voltage level of the data signal, the charge of the pixel (pixel electrode and common electrode) 105 is maintained even after the TFT 110 is cut off, and the image by the electrophoretic particles 120 is maintained. Each pixel 105 performs display in accordance with the voltage level of the data signal, thereby displaying an image.

  As described above, according to the third embodiment, since an appropriate driving waveform can be supplied to the electrophoretic element 120 using the temperature sensor 1 (1b) having a small mounting area, it is mounted on a small portable device such as a wristwatch. It is suitable as an electrophoresis apparatus.

(Embodiment 4)
Embodiment 4 of this invention shows the application example of the electronic device to which the temperature sensor of this invention is applied.
FIG. 16 is a perspective view illustrating a specific example of an electronic apparatus to which the electrophoresis device described in Embodiment 3 is applied.

FIG. 16A is a perspective view illustrating an electronic book that is an example of the electronic apparatus.
The electronic book 1000 includes a book-shaped frame 1001, a cover 1002 that can be rotated (openable and closable) with respect to the frame 1001, an operation unit 1003, and the electrophoresis apparatus according to the present invention. Display unit 1004.

FIG. 16B is a perspective view illustrating a wrist watch which is an example of an electronic apparatus.
The wristwatch 1100 includes a display unit 1101 configured by the electrophoresis apparatus according to the present invention.

FIG. 16C is a perspective view illustrating electronic paper which is an example of an electronic apparatus.
The electronic paper 1200 includes a main body unit 1201 configured by a rewritable sheet having the same texture and flexibility as paper, and a display unit 1202 configured by the electrophoresis apparatus according to the present embodiment.

  The range of electronic devices to which the electrophoretic device can be applied is not limited to this, and includes a wide range of devices that utilize changes in visual color tone accompanying the movement of charged particles. For example, in addition to the above-described devices, those belonging to real estate such as wall surfaces to which an electrophoretic film is bonded, and those belonging to moving bodies such as vehicles, flying objects, and ships are also applicable.

  In addition, the electronic device is not necessarily provided with an electrophoretic device, and any device that performs control or display from anything based on the temperature detected by the temperature sensor is assumed.

(Modification)
The present invention is not limited to the above-described embodiment, and can be variously modified and applied.
For example, in the above-described embodiment, the ring oscillator is exemplified as the oscillation circuit, but the present invention is not limited to this. If the oscillation circuit changes its oscillation frequency as the temperature rises, it is possible to apply the present invention. For example, an oscillation circuit that uses the hysteresis characteristics of an integrated circuit, an unstable multivibrator, or the like can be used.

The block diagram of the temperature sensor in Embodiment 1. Configuration diagram of a ring oscillator as an example of the oscillation circuit in the first embodiment Oscillation frequency-temperature characteristics that change in response to changes in the power supply voltage supplied to the oscillation circuit Explanatory drawing of the measuring method of a counter. (A) is a 1st measuring method, (b) is a 2nd measuring method. Example of oscillation frequency-temperature characteristics of an oscillation circuit calibrated by the manufacturing method according to this embodiment Example of oscillation frequency vs. temperature characteristics of oscillation circuit when calibration process is not performed 6 is a flowchart showing a manufacturing method (first calibration method) of the temperature sensor according to the first embodiment. Illustration of transistor threshold voltage variation and limit sample Example of measurement result of oscillation lower limit voltage in step S100 of the first embodiment Example of measurement result of reference frequency in step S103 of the first embodiment Example of measurement result of power supply voltage for manufactured product in step S104 of the first embodiment Block diagram of temperature sensor in embodiment 2 9 is a flowchart showing a temperature sensor manufacturing method (second calibration method) according to the second embodiment. Block diagram of an electrophoresis apparatus according to Embodiment 3 Relationship diagram between temperature and appropriate driving voltage in electrophoretic device 7A and 7B are perspective views of an electronic device according to a fourth embodiment, in which FIG. 9A is an electronic book, FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1b ... Temperature sensor, 10 ... Ring oscillator, 11, 11b ... Power supply circuit, 12 ... Selection part, 13 ... Power supply voltage memory | storage part, 20 ... Counter, 21 ... Reference signal oscillator, 30 ... Count value temperature conversion circuit , 31 ... Count temperature related information storage unit, 40 ... Display, 50 ... Drive waveform control circuit, 100 ... Element substrate, 101 ... Scan line, 102 ... Data line, 105 ... Pixel, 120 ... Electrophoretic element, 130 ... Scan Line drive circuit, 140 ... Data line drive circuit, 140 ... Data line drive circuit, 150 ... Counter electrode modulation circuit, 300 ... Controller, 1000 ... Electronic book, 1001 ... Frame, 1002 ... Cover, 1003 ... Operation unit, 1004 ... Display , 1100 ... wristwatch, 1101 ... display part, 1200 ... electronic paper, 1201 ... main body part, 1202 ... display part, A ... display panel C, capacitor, Cs, holding capacitor, Vdc, power supply voltage, focs, oscillation frequency, fref, reference frequency, INV, inverter, Pref, reference point, Socs, oscillation signal, Sref, reference signal, TR, measurement target temperature Range, Tr1 ... first transistor, Tr2 ... second transistor, tref ... reference temperature, Δt ... maximum measurement error,

Claims (13)

An oscillation circuit;
A power supply circuit for supplying a predetermined power supply voltage to the oscillation circuit;
A temperature specifying circuit for specifying a temperature based on the oscillation frequency of the oscillation circuit,
The oscillation circuit is configured such that the oscillation frequency increases in response to an increase in temperature,
The power supply circuit is configured to supply a power supply voltage for causing the oscillation circuit to oscillate at a predetermined reference frequency at a predetermined reference temperature.
The temperature specifying circuit is configured to specify a temperature based on relation information between an oscillation frequency of the oscillation circuit and the temperature;
Temperature sensor. The power supply circuit sets the power supply voltage to be applied to the oscillation circuit within a temperature characteristic range in which an oscillation frequency increases with an increase in temperature.
The temperature sensor according to claim 1. The oscillation circuit is a ring oscillator including an inverter,
The inverter is configured by connecting in series a first transistor having a first polarity between the power supply voltage and the ground potential and a second transistor having a second polarity opposite to the first polarity. And
The power supply circuit sets the power supply voltage to be applied to the ring oscillator higher than a threshold voltage of the first transistor and the second transistor;
The temperature sensor according to claim 2. In the power supply circuit, a power supply voltage for oscillating at the reference frequency at the reference temperature is stored for each sample of the oscillation circuit having various threshold values within an allowable range. And
Furthermore, a selection unit for setting which sample the oscillation circuit belongs to is provided,
The power supply circuit supplies the power supply voltage stored for the sample corresponding to the setting of the selection unit to the oscillation circuit;
The temperature sensor according to claim 1. The temperature specifying circuit includes a counter and a count value temperature conversion circuit that converts a count value of the counter into temperature information,
The counter receives a reference signal having a frequency higher than the oscillation frequency of the oscillation circuit, and outputs the number of periods of the reference signal that falls within a certain period of the oscillation signal from the oscillation circuit as the count value.
The temperature sensor according to any one of claims 1 to 4. The temperature specifying circuit includes a counter and a count value temperature conversion circuit that converts a count value of the counter into temperature information,
The counter receives a reference signal having a frequency lower than the oscillation frequency of the oscillation circuit,
Outputting the number of periods of the oscillation signal from the oscillation circuit that enters the fixed period of the reference signal as the count value;
The temperature sensor according to any one of claims 1 to 4. An electrophoretic element; a drive waveform control circuit that changes a drive waveform based on the temperature specified by the temperature sensor; and a drive circuit that drives the electrophoretic element with the drive waveform.
An electrophoresis apparatus comprising the temperature sensor according to claim 1.   The electronic device provided with the temperature sensor of any one of Claims 1 thru | or 6. A method of manufacturing a temperature sensor including an oscillation circuit,
The oscillation circuit has an oscillation frequency that increases as the temperature rises.
Measuring a lower limit voltage at which oscillation stops for each sample of an oscillation circuit with various variations in threshold value within an allowable range;
Identifying the sample with the highest lower limit voltage as a reference sample;
Identifying as a reference voltage a voltage at which all the samples can oscillate based on the measured lower limit voltage;
Identifying an oscillation frequency as a reference frequency when the reference voltage is applied to the reference sample at a predetermined reference temperature;
For the oscillation circuit to be adjusted, a step of setting a power supply voltage for oscillating at the reference frequency at the reference temperature;
A method for manufacturing a temperature sensor, comprising: The step of setting the power supply voltage includes:
Identifying a power supply voltage for oscillating at the reference frequency at the reference temperature for the oscillation circuit to be adjusted;
Setting the power supply voltage for the specified oscillation circuit to be adjusted as the power supply voltage of the oscillation circuit;
The manufacturing method of the temperature sensor of Claim 9 provided with these. The step of setting the power supply voltage includes:
For a sample other than the reference sample, identifying a power supply voltage for oscillating at the reference frequency at the reference temperature;
Selecting a sample having a threshold value corresponding to the oscillation circuit to be adjusted;
Setting the power supply voltage specified for the selected sample as a power supply voltage for the oscillation circuit to be adjusted;
The manufacturing method of the temperature sensor of Claim 9 provided with these.   10. The temperature according to claim 9, wherein the step of specifying the reference voltage specifies, as the reference voltage, a voltage obtained by adding a predetermined margin to the lower limit voltage that is the highest among the lower limit voltages indicated by a plurality of reference samples. Sensor manufacturing method.   The temperature sensor manufacturing method according to claim 9, wherein the step of specifying the reference frequency specifies the highest frequency among the oscillation frequencies indicated by a plurality of reference samples as the reference frequency.