KR20080090275A - Apparatus and method for measurement of temperature using oscillators - Google Patents

Abstract

A temperature measuring apparatus and method using oscillators are provided to reduce power consumption by applying a power saving operation mode to operate the oscillation circuit when needed only. An apparatus for measuring temperature comprises a first oscillation circuit(201), a second oscillation circuit(203), a MUX(205), and a frequency to digital converter(207). The MUX selectively passes a first frequency signal output from the first oscillation circuit and a second frequency signal output from a second frequency signal. The frequency to digital converter converts the frequency difference between the first frequency signal and the second frequency signal to a digital code.

Description

Apparatus and method for measurement of temperature using oscillators

The present invention relates to a temperature measuring apparatus and method using an oscillation circuit. Specifically, the present invention relates to an apparatus and method for measuring temperature by using a difference in frequency between signals generated in a temperature sensitive oscillator circuit and a temperature sensitive oscillator circuit.

The configuration of a temperature sensor using a conventional Complementary Metal Oxide Semiconductor (CMOS) process is shown in FIG. Referring to FIG. 1, a conventional CMOS temperature sensor includes a temperature detector 101, a reference unit 103, and an analog-to-digital converter (ADC). The temperature sensor 101 is a part that detects a temperature. The temperature detector 101 uses a portion of a bandgap reference circuit so that the output voltage appears in proportion to the temperature, or the delayed amount by using a plurality of delay lines such as an inverter is applied to the temperature. Circuits designed to appear proportionally are used or designed to generate signals in proportion to temperature using special devices. The reference unit 103 performs a function of providing a constant reference even when the temperature changes. The reference unit 103 is mostly implemented using a bandgap reference or using a delay line which is less sensitive to temperature. The analog-to-digital converter 105 converts an analog signal received from the temperature sensing unit 101 and the reference unit 103 into a digital signal. The analog-to-digital converter 105 is mostly using a sigma-delta type, a successive-approximation register type, or a dual-integration type analog / digital converter. In addition, a comparator or a TDC ( There are some implementations using Time to Digital Converter.

However, the temperature sensors fabricated using the conventional circuit techniques listed above have disadvantages of being sensitive to noise and consuming high power due to their analog characteristics. In addition, the temperature sensors fabricated by the above circuit techniques are very large in size due to complex implementation methods, and are integrated with other electronic circuits such as DRAM (Dynamic RAM) or microprocessors, thereby providing a single chip system. ; SoC) is difficult to implement.

An object of the present invention for solving the above problems is to provide a CMOS temperature sensor and a temperature measuring method that can significantly reduce the size and significantly reduce the power consumption.

Another object of the present invention is to reduce the power wasted during the extraction of the temperature, and after the temperature is extracted to block the operation of the oscillation circuit to prevent unnecessary power consumption and to prevent the generation of noise, to efficiently measure the temperature It is an object of the present invention to provide an apparatus and method.

It is still another object of the present invention to provide a temperature measuring apparatus and method having a high resolution by using a multi-phase signal generated in an oscillator circuit generating a multi-phase signal.

In order to achieve the above objects, in accordance with an aspect of the present invention; A second oscillation circuit; A mux for selectively passing a first frequency signal output from the first oscillator circuit and a second frequency signal output from the second oscillator circuit; And a frequency / digital converter for converting a difference between the first frequency signal and the second frequency signal into a digital code.

In a preferred embodiment, the first oscillator circuit is a temperature sensitive oscillator circuit, and the second oscillator circuit is an oscillator circuit which is not temperature sensitive. In addition, the second oscillator circuit is characterized in that the first oscillator circuit is configured by adding a circuit for compensating for changes due to temperature. The first oscillator circuit and the second oscillator circuit may be gated oscillator circuits. In addition, the first oscillator circuit is characterized in that the oscillator circuit for generating a multi-phase frequency signal. The apparatus may further include a fine resolution generating circuit for generating a fine resolution code using the multi-phase frequency signal. The frequency / digital converter may further include a countdown operation when the first frequency signal is input and a countdown operation when the second frequency signal is input; And a count buffer outputting the final value counted by the up-down counter to the outside. In addition, one bit of the up-down counter may include a mux to which an up / down control signal is input, an xor to which a reset control signal is input, and an AND and a flip-flop to which a run / hold control signal is input. The counter buffer may include a plurality of buffers, and a power control transistor is coupled to a power supply of a first buffer stage among the plurality of buffers. In addition, the first oscillator circuit and the second oscillator circuit is characterized in that the operation by the enable signal, the operation is stopped by the disable signal.

According to another aspect of the present invention, there is provided a method of measuring temperature in a temperature sensor including a first oscillation circuit and a second oscillation circuit, the method comprising: operating the first oscillation circuit and the second oscillation circuit; Selectively passing a first frequency signal output from the first oscillator circuit and a second frequency signal output from the second oscillator circuit; And converting a difference between the first frequency signal and the second frequency signal into a digital code, wherein the digital code corresponds to a temperature to be measured.

In a preferred embodiment, the first oscillator circuit is a temperature sensitive oscillator circuit, and the second oscillator circuit is an oscillator circuit which is not temperature sensitive. The method may further include stopping the operation of the first oscillator circuit and the second oscillator circuit by a disable signal. The method is further characterized in that the first oscillating circuit and the second oscillating circuit are gated oscillating circuits. The method is further characterized in that the first oscillator circuit is an oscillator circuit for generating a multi-phase frequency signal. The method may further include generating a fine resolution code using the multi-phase frequency signal.

The CMOS temperature sensor according to the present invention is a temperature-sensitive oscillator circuit, a temperature-sensitive oscillator circuit, a frequency / digital converter for converting a mux and a frequency signal inputted through a frequency signal from each oscillator circuit into digital codes. The simple configuration of (FDC) has the advantage that the size can be significantly reduced compared to the existing temperature sensor.

In addition, according to the present invention, since the up-down counter bit of the frequency-to-digital converter (FDC) is adjusted according to the resolution of the temperature sensing, the resolution can be easily adjusted to meet the specifications of the desired product.

In addition, according to the present invention, when the temperature-sensitive oscillation circuit generates a multi-phase frequency signal, the fine resolution generation circuit using the multi-phase signal has an advantage of significantly increasing the resolution without increasing power consumption.

In addition, according to the present invention, the counter buffer operation of the frequency-to-digital converter (FDC) prevents unnecessary intermediate signals from being passed out and only digital codes indicating the final temperature are passed out, thereby reducing unnecessary power consumption.

In addition, according to the present invention, by applying the power saving operation mode to the entire circuit of the temperature sensor there is an advantage that can reduce the overall operating power consumption by operating the temperature sensor only when necessary and not operating the temperature sensor when not necessary.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of a temperature sensor using an oscillation circuit according to an embodiment of the present invention.

Referring to FIG. 2, the temperature sensor according to the present invention includes two oscillation circuits 201 and 203, a mux 205, and a frequency-to-digital converter (FDC). . The temperature sensor may be manufactured using a complementary metal oxide semiconductor (CMOS) semiconductor process.

One of the two oscillator circuits is a temperature sensitive oscillator circuit 201 and the other is a temperature sensitive oscillator circuit 203. The temperature sensitive oscillator circuit 201 may be configured as a voltage controlled oscillator circuit or a ring oscillator circuit. The temperature-sensitive oscillation circuit 203 is configured by additionally mounting a circuit for compensating for changes in temperature in a circuit constituting the temperature-sensitive oscillation circuit 201. In this case, it is preferable that the remaining part of the oscillation circuit 203 which is not sensitive to temperature is configured in the same manner as the oscillation circuit 201 which is sensitive to the temperature change except for a circuit that compensates for the temperature change. This is because only the variables for the temperature (Temperature Variation) can be obtained, which eliminates the errors caused by the process variation or the voltage variation.

The output frequencies of the two oscillation circuits 201 and 203 according to the temperature are shown in FIG. 4. Looking at the graph of Figure 4, the horizontal axis represents the temperature, the vertical axis represents the frequency. In the graph, it can be seen that the output frequency 301 of the temperature sensitive oscillator circuit 201 decreases as the temperature increases, and the output frequency 303 of the temperature sensitive oscillator circuit 203 is independent of temperature change. have. The difference between the output frequencies of the two oscillation circuits 201 and 203 is shown in FIG. 5. In the temperature sensor according to the present invention, the temperature is detected by using the temperature characteristic of the frequencies of the oscillation circuits 201 and 203.

Both the temperature sensitive oscillator circuit 201 and the temperature sensitive oscillator circuit 203 are determined to be operated through an enable / disable signal. When the enable signal is input, the oscillator circuits 201 and 203 operate to detect the temperature. When the temperature detection is completed and no further operation is required, the disable signal is sent to the oscillator circuits 201 and 203. The input will stop.

The two oscillator circuits 201 and 203 are formed in the form of gated oscillator as shown in FIG. 3 by using the temperature sensitive oscillator circuit 201 and the temperature sensitive oscillator circuit 203 sequentially operated. In this case, when the operation is not necessary even in the temperature detection step, the operation of the two oscillation circuits is cut off, so that unnecessary power consumption can be cut off. By implementing such a power saving operation mode in the temperature sensor, the temperature sensor is operated only when necessary, otherwise the circuit of the temperature sensor is turned off, thereby greatly reducing the total power consumption, and the two oscillation circuits 201 and 203. ) Can cut off the noise generated by unnecessarily continuing operation.

The mux 205 receives a frequency signal output from the two oscillating circuits 201 and 203 and selectively outputs the frequency signal to the frequency / digital converter 207.

The frequency / digital converter 207 converts the frequency signal output from the mux 205 into a digital code. That is, the frequency-to-digital converter 207 selectively receives the frequency signals of the two oscillation circuits 201 and 203 through the mux 205 and serves to quantify the difference between the two frequency signals. In this case, the frequency difference between the two signals corresponds to the temperature to be measured immediately.

6 is a fine resolution generating circuit 209 using the multi-phase frequency signal when the oscillator is characterized in that the first oscillator 201 generates a multi-phase frequency signal according to another embodiment of the present invention. It is a block diagram of the temperature sensor that contains. The up / down counter 601 and the buffer 603 of FIG. 6 are included in the frequency / digital converter 207, which will be described later with reference to FIG. 10.

The fine resolution generating circuit 209 is a circuit using a multi-phase frequency signal generated by the temperature-sensitive oscillation circuit 201, and is a time point at which the temperature-sensitive oscillating circuit finishes its operation according to a signal of the external controller 211. The signal position is identified and the fine resolution is output as a digital code. The external controller 211 equals the time for counting the rising clock of the signal from the oscillation circuit 203 which is not sensitive to the temperature and the time for counting the rising clock of the signal from the oscillating circuit 201 which is sensitive to the temperature. The role of distribution. The resolution may be dramatically increased by the fine resolution generating circuit 209 without increasing power consumption.

FIG. 7 illustrates that when the temperature sensitive first oscillator circuit 201 generates a multi-phase frequency signal, the fine resolution generator 209 outputs the multi-phase frequency signal. An example of generating a fine code using

In FIG. 7, for example, the temperature sensitive oscillator 201 generates a multi-phase signal having three different phases. The multi-phase signal having three different phases has a single temperature sensitive oscillator circuit. It plays a role of dividing one period into eight parts when generating a phase signal. That is, when one phase signal is used, information between the rising signals is not available, but when the three multi-phase signals are used, the up / down direction determination signal 701 sent out from the external controller 211 is used. Captures the position at the point of change of direction from the temperature sensitive oscillator circuit 201 to the temperature sensitive oscillator circuit 203, so that the fine code generating circuit 209 generates a fine code at that point. As a result, the information between the rising signals is made available and a higher resolution can be ensured.

It can be seen that the microcode of the temperature sensitive oscillation circuit at the time point 703 at which the external controller 211 in FIG. 7 changes the direction of the up / down counter is represented by [1 10]. As described above, it is understood that the resolution is increased by allowing the fine code generation circuit 209 using the multi-phase signal to display parts that cannot be represented more precisely when using one phase signal.

8 is a graph showing a difference in resolution in the case of including and not including the fine code generation circuit according to an exemplary embodiment of the present invention.

Fig. 8A shows the resolution when no fine code generation circuit is included, and Fig. 8B shows the resolution when fine code generation circuit is included.

Referring to FIG. 8 (a), the digital clock 801a counting the rising clock of the signal from the temperature-sensitive oscillation circuit 201 and the rising clock of the signal from the oscillation circuit 203 that are not temperature-sensitive. It can be seen that the difference between the counted digital outputs 803a becomes the temperature 805a to be measured. Therefore, in the case of not including the fine code generation circuit, the resolution becomes the difference 807a of the outputtable temperatures.

Referring to FIG. 8B in the same manner as above, the resolution in the case of including the fine code generation circuit becomes the difference 807b of the outputable temperatures.

Therefore, when the micro code generation circuit 209 is included, the first oscillation circuit 201 and the second oscillation circuit which are not sensitive to the temperature are higher than those when the micro code generation circuit 209 is not included. It can be seen that the difference in the digital output of the signals from 203 can be represented more finely. Accordingly, the resolution representing the temperature can be increased.

9 is a circuit diagram of a temperature insensitive oscillating circuit according to a preferred embodiment of the present invention.

A process of compensating for the change in temperature in the oscillation circuit which is not sensitive to temperature will be described with reference to FIG. 9.

In the circuit diagram, the current flowing through P3 is expressed by Equation 1 below.

I _{D , P3} : Current flowing in the drain of the PMOS transistor P3

μ: carrier mobility

C _OX : Oxide capacitance forming a silicon insulation layer

W: Width of MOS

L: Gate length of MOS

V _{GS , P3} : Gate source voltage of PMOS transistor P3

V _T : Threshold voltage of MOS transistor

λ: The degree to which the drain voltage affects current by channel length modulation

The <Equation 1> is the amount of current in a MOS controlled by V _GS, and operates that the V _GS is the V or more _T be the MOS transistor. In addition, the V _GS multiplied by λ in Equation 1 is actually V _DS, but may be expressed as Equation 1 because drain and gate are connected.

Meanwhile, the current according to the temperature of Equation 1 may be expressed as Equation 2 below.

μ ₀ : Carrier mobility constant at constant temperature

T: Absolute temperature value

T ₀ : Constant absolute temperature value

k, m: device information constant for the material

α: Constant for calculating the amount of current change with temperature

If Equation 2 is differentiated with respect to temperature and the condition satisfying Equation 3 is found, Equation 4 is obtained.

Substituting Equation (4) into Equation (2) is the same as Equation (5).

Looking at Equation 5, it can be seen that the current flowing through the transistor P3 does not depend on the temperature T. Therefore, if the temperature-insensitive currents I _{D and P3} are supplied to the oscillating circuit in the dotted line through the current mirror consisting of P1 and P2 and the current mirror consisting of N1 and N2, the oscillating circuit insensitive to the temperature The characteristic is not dependent on temperature.

10 is a block diagram of a frequency-to-digital converter (FDC) according to a preferred embodiment of the present invention.

Referring to FIG. 10, the frequency / digital converter according to the present invention includes an up-down counter 601 and a counter buffer 603. The up-down converter 601 is a reset signal stage for initializing a counter, an up / down signal stage for determining whether the counter counts up or counts down, and the counter continues to count or a current value. It is connected to the Run / Hold signal stage which decides whether or not to be maintained. The run / hold signal terminal is connected to the count buffer 603 to control whether the count buffer 603 outputs an internal signal as an external signal.

When the run signal is input to the up-down counter 601, the up-down counter receives a signal MUX_out output from the mux. The output signal of the mux is a signal in which a signal of a frequency generated from two oscillating circuits is selectively passed through the mux. First, when the output signal of the mux is a frequency signal from the oscillation circuit sensitive to temperature, the up-down counter 601 performs a count up operation by controlling the up signal. On the other hand, when the output signal of the mux is a frequency signal from the oscillator circuit which is not sensitive to temperature, the up-down counter 601 performs a count up operation on the frequency signal from the oscillator circuit which is sensitive to temperature by controlling the down signal. A countdown operation is performed for the same time to count the difference between the two frequencies. When the digital encoding process between the two frequencies is completed in the up-down counter 601, a Hold signal is input to stop the operation of the up-down counter 601 and all the oscillation circuits and maintain the current value. On the other hand, when the Hold signal is input, the counter buffer 603 receives the value held by the up-down counter 601 and outputs the value to the outside.

The counter buffer 603 and the up-down counter 601 are controlled by the same Run / Hold signal but operate in opposite directions. That is, when the Run signal is input, the up-down counter 601 performs a count up or count down operation, but the counter buffer 603 stops the operation and does not output an internal change to the outside. On the contrary, when the Hold signal is input, the up-down counter 601 stops the operation and maintains the current value, and the counter buffer 603 outputs the internal value to the outside. Through this operation it is possible to significantly lower the power consumption without need.

On the other hand, the reset signal is used for initializing the up-down counter 601 when the temperature is measured.

11 is a detailed block diagram of a frequency / digital converter according to an embodiment of the present invention. The frequency / digital converter in FIG. 11 is an example in which a 10-bit updown counter is used.

Referring to FIG. 11, one bit of the up-down converter of the frequency / digital converter includes XOR, flip-flop, mux, and AND. Here, the Up / Down signal is input to the mux, a Reset signal is input to the XOR, and a Run / Hold signal is input to the AND as a control signal.

In order to increase the resolution of the temperature sensing, the number of bits of the up-down converter of the frequency / digital converter may be increased. Therefore, the resolution can be adjusted to meet the specifications of the desired temperature sensor.

12 is a block diagram of a counter buffer according to an embodiment of the present invention.

Referring to FIG. 12, the counter buffer according to the present invention uses as many buffer stages or inverter stages as necessary to drive the load of the final stage, and attaches a control transistor to the power supply of the first buffer stage. It is configured to control power supply of buffer stage by Run / Hold signal. When the run signal is input, the control transistor is turned off to stop the operation of the buffer stage. When the hold signal is input, the control transistor is operated so that the buffer terminal can send out the signal to the outside. Therefore, no matter how the signal in front of the buffer stage is changed, the counter buffer outputs only the final output to the outside, thereby greatly reducing power consumption.

13 is a flowchart illustrating a procedure of measuring a temperature in a temperature sensor using an oscillation circuit according to an exemplary embodiment of the present invention.

Referring to FIG. 13, first, a temperature sensor according to the present invention drives a temperature sensitive oscillator circuit and a temperature sensitive oscillator circuit when an enable signal is input for temperature measurement (step 901). At this time, the two oscillator circuits generate respective frequency signals in accordance with the temperature. Thereafter, the mux of the temperature sensor selectively passes through the two frequency signals output from the two oscillation circuits and outputs them to the frequency / digital converter inside the temperature sensor (step 903). The frequency / digital converter then converts the frequency signal input from the mux into a digital code (step 905). In this case, the converted digital code corresponds to a temperature to be measured as a value corresponding to a difference between the two frequency signals.

When the temperature measurement is completed, the temperature sensor enters a power saving operation mode by stopping the operation of the two oscillating circuits and the up-down counter by a disable signal (step 907).

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

1 is a block diagram of a temperature sensor using a conventional Complementary Metal Oxide Semiconductor (CMOS) process.

2 is a block diagram of a temperature sensor using an oscillation circuit according to an embodiment of the present invention.

3 is a block diagram of a gated oscillation circuit according to a preferred embodiment of the present invention.

4 is a characteristic graph according to a temperature of a frequency signal generated in a temperature-sensitive oscillation circuit and a temperature-sensitive oscillation circuit according to a preferred embodiment of the present invention.

5 is a graph showing the difference between frequency signal characteristics generated in a temperature sensitive oscillator circuit and a temperature sensitive oscillator circuit according to an exemplary embodiment of the present invention.

6 is a configuration diagram of a temperature sensor further comprising a fine resolution generating circuit using the multi-phase frequency signal when the first oscillator is an oscillator for generating a multi-phase frequency signal according to an embodiment of the present invention.

7 is an exemplary diagram illustrating a process of generating a fine code using a multi-phase frequency signal by a fine resolution generating circuit according to an exemplary embodiment of the present invention.

8 is a comparison graph illustrating an increase in resolution in the case of including a fine code generation circuit according to an exemplary embodiment of the present invention.

9 is a circuit diagram of a temperature insensitive oscillation circuit according to one preferred embodiment of the present invention.

10 is a block diagram of a frequency-to-digital converter (FDC) according to an embodiment of the present invention.

11 is a detailed block diagram of a frequency / digital converter according to an embodiment of the present invention.

12 is a block diagram of a counter buffer according to an embodiment of the present invention.

13 is a flowchart illustrating a procedure for measuring temperature in a temperature sensor using an oscillation circuit according to an embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

201: temperature sensitive oscillation circuit

203: temperature sensitive oscillation circuit

205: MUX

207: Frequency-to-Digital Converter (FDC)

209: fine resolution generating circuit using multi-phase frequency signal

211: external controller

601: up-down counter

603: counter buffer

Claims (16)

A first oscillation circuit; A second oscillation circuit; A mux for selectively passing a first frequency signal output from the first oscillator circuit and a second frequency signal output from the second oscillator circuit; And And a frequency / digital converter for converting the frequency difference between the first frequency signal and the second frequency signal into a digital code. The method of claim 1, Wherein the first oscillator circuit is a temperature sensitive oscillator circuit, and the second oscillator circuit is a temperature sensitive oscillator circuit. Temperature sensor, characterized in that. The method of claim 2, The second oscillation circuit is configured by adding a circuit for compensating for the change due to temperature to the first oscillation circuit. Temperature sensor, characterized in that. The method of claim 2, The first oscillation circuit and the second oscillation circuit being gated oscillation circuits Temperature sensor, characterized in that. The method of claim 2, The first oscillator circuit is an oscillator circuit for generating a multi-phase frequency signal Temperature sensor, characterized in that. The method of claim 5, Further comprising a fine resolution generating circuit for generating a fine resolution code by using the multi-phase frequency signal Temperature sensor, characterized in that. The method of claim 2, The frequency / digital converter An up-down counter that performs a count up operation when the first frequency signal is input and performs a count down operation when the second frequency signal is input; And A count buffer for outputting the final value counted by the up-down counter to the outside Temperature sensor, characterized in that. The method of claim 7, wherein One bit of the up-down counter includes a mux to which an up / down control signal is input, an xor to which a reset control signal is input, and an AND and flip-flop to which a run / hold control signal is input. Temperature sensor, characterized in that. The method of claim 7, wherein The counter buffer includes a plurality of buffers, the power control transistor is coupled to the power supply of the first buffer stage of the plurality of buffers Temperature sensor, characterized in that. The method of claim 1, The first oscillator circuit and the second oscillator circuit are operated by the enable signal, the operation is stopped by the disable signal Temperature sensor, characterized in that. In the method for measuring the temperature in a temperature sensor comprising a first oscillation circuit and a second oscillation circuit, Operating the first oscillator circuit and the second oscillator circuit; Selectively passing a first frequency signal output from the first oscillator circuit and a second frequency signal output from the second oscillator circuit; And Converting the difference between the first frequency signal and the second frequency signal into a digital code; The digital code corresponds to the temperature to be measured Temperature measuring method, characterized in that. The method of claim 11, Wherein the first oscillator circuit is a temperature sensitive oscillator circuit, and the second oscillator circuit is a temperature sensitive oscillator circuit. Temperature measuring method, characterized in that. The method of claim 11, Stopping the operation of the first oscillator circuit and the second oscillator circuit by a disable signal; Temperature measuring method, characterized in that. The method of claim 11, The first oscillation circuit and the second oscillation circuit being gated oscillation circuits Temperature measuring method, characterized in that. The method of claim 11, The first oscillator circuit is an oscillator circuit for generating a multi-phase frequency signal Temperature measuring method, characterized in that. The method of claim 15, Generating a fine resolution code using the multi-phase frequency signal Temperature measuring method, characterized in that.

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