JP2012221301A - Electronic apparatus, control method for the same, and semiconductor integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic apparatus capable of keeping an operation voltage of a built-in semiconductor integrated circuit low.SOLUTION: An electronic apparatus 1 includes: a power circuit 13; a semiconductor integrated circuit 10 that operates by a supply voltage to be supplied from the power circuit 13; and a temperature sensor 11 that measures the temperature of the semiconductor integrated circuit 10. The power circuit 13 decreases the supply voltage in accordance with a rise in the temperature to be measured.

Description

  The present invention relates to a semiconductor integrated circuit having a built-in CMOS, an electronic apparatus including the semiconductor integrated circuit, and a control method thereof.

  For example, a semiconductor integrated circuit including a CMOS such as a central processing unit (CPU) or an SOC (System-on-a-chip) is widely used as a component of an electronic device (see, for example, Patent Document 1).

US Pat. No. 6,518,823

  In recent years, with the miniaturization of CMOS, a tendency different from the conventional product appears in the temperature dependence of the performance. However, a method for efficiently using a semiconductor integrated circuit in accordance with such characteristics has not yet been sufficiently considered.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a semiconductor integrated circuit capable of keeping operating voltage low, an electronic device including the semiconductor integrated circuit, and a control method thereof. There is to do.

  An electronic apparatus according to the present invention includes a power supply circuit, a semiconductor integrated circuit that operates with a supply voltage supplied from the power supply circuit, and a temperature sensor that measures a temperature of the semiconductor integrated circuit, and the power supply circuit includes: The supply voltage is lowered in accordance with an increase in the measured temperature.

  In the electronic device, the power supply circuit may lower the supply voltage by a predetermined decrease width when the measured temperature becomes a predetermined threshold value or more.

  According to another aspect of the invention, there is provided an electronic device control method including an electronic power source circuit, a semiconductor integrated circuit that operates with a supply voltage supplied from the power source circuit, and a temperature sensor that measures a temperature of the semiconductor integrated circuit. A device control method, comprising: obtaining the measured temperature; and lowering a supply voltage that the power supply circuit supplies to the semiconductor integrated circuit in response to an increase in the obtained temperature. It is characterized by.

  The semiconductor integrated circuit according to the present invention is a semiconductor integrated circuit that operates by a supply voltage supplied from a power supply circuit, and includes a temperature sensor that measures the temperature of the semiconductor integrated circuit, and a rise in the measured temperature. And means for requesting the power supply circuit to lower the supply voltage accordingly.

1 is a schematic configuration diagram of an electronic device including a semiconductor integrated circuit according to an embodiment of the present invention. It is a figure which shows typically the time change of the operating frequency f at the time of the operating frequency f change in the prior art example, and the supply voltage Vp. It is a figure which shows typically the time change of the operating frequency f at the time of the operating frequency f change in this embodiment, and the supply voltage Vp. It is a graph which shows the relationship between the frequency | count N of change at the time of the operating frequency f change, the required time R which the said change requires, and the target voltage Vp2. It is a graph which shows typically the relation between lower limit voltage Vl of operating frequency f, and temperature T. It is a graph which compares the power consumption when not performing with the case where voltage control according to temperature is performed.

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

[Configuration of electronic equipment]
FIG. 1 is a configuration diagram showing a schematic circuit configuration of an electronic apparatus 1 including a semiconductor integrated circuit 10 according to an embodiment of the present invention. The electronic device 1 includes a semiconductor integrated circuit 10, a temperature sensor 11, a temperature controller 12, a power supply circuit 13, and a power supply control circuit 14.

  The semiconductor integrated circuit 10 is an integrated circuit including a complementary metal oxide semiconductor (CMOS), and may be, for example, a CPU or an SOC. The semiconductor integrated circuit 10 operates with the supply voltage Vp supplied from the power supply circuit 13. In the following, it is assumed that the semiconductor integrated circuit 10 is an arithmetic device that performs various types of information processing in accordance with programs stored in an internal memory or an external memory. The semiconductor integrated circuit 10 can internally change its own operating frequency f in accordance with the operation content (the content of the program to be executed here). When changing its own operating frequency f, the semiconductor integrated circuit 10 outputs an instruction for changing the supply voltage Vp to the power supply control circuit 14 in accordance with the change.

  The semiconductor integrated circuit 10 includes a temperature sensor 11. The temperature sensor 11 measures the temperature of the semiconductor integrated circuit 10 and outputs an electrical signal indicating the result to the temperature controller 12.

  The temperature controller 12 receives a signal output from the temperature sensor 11 and outputs information representing the temperature T of the semiconductor integrated circuit 10 obtained in accordance with the received signal to the power supply control circuit 14.

  The power supply circuit 13 includes, for example, a power supply IC that functions as a switching regulator. The power supply circuit 13 is a power supply source outside the electronic device 1 (for example, a commercial AC power supply or a USB host device), or a battery built in the electronic device 1. The power supplied from the above is converted into a given voltage and supplied to each part of the electronic device 1. In particular, the power supply circuit 13 supplies power to the semiconductor integrated circuit 10 at a supply voltage Vp according to an instruction input from the power supply control circuit 14.

  The power supply control circuit 14 is a circuit that controls the operation of the power supply circuit 13 and is configured by a microcomputer or the like. In the present embodiment, the power supply control circuit 14 is based on an instruction according to a change in the operating frequency f input from the semiconductor integrated circuit 10 and / or information indicating the temperature T of the semiconductor integrated circuit 10 input from the temperature controller 12. The supply voltage Vp is determined, and the power supply circuit 13 is instructed to supply power to the semiconductor integrated circuit 10 with the determined supply voltage Vp.

[Changing operating frequency]
Next, control when the semiconductor integrated circuit 10 changes the operating frequency f in the present embodiment will be described.

  In general, the lower limit value of the supply voltage Vp to be supplied to the semiconductor integrated circuit 10 (the minimum voltage value necessary for normal operation of the semiconductor integrated circuit 10) varies according to the operating frequency f. That is, the higher the operating frequency f, the larger the value of the necessary supply voltage Vp. Therefore, in order to reduce the power consumption of the semiconductor integrated circuit 10, when the operating frequency f is dynamically changed, the supply voltage Vp is also changed accordingly and before and after the change of the operating frequency f, the lower limit value is possible. It is desirable to supply the semiconductor integrated circuit 10 with a supply voltage Vp close to. Specifically, when the semiconductor integrated circuit 10 changes the operating frequency f from the initial frequency f1 to the target frequency f2 (> f1), the supply voltage Vp also corresponds from the initial voltage Vp1 corresponding to the initial frequency f1 to the target frequency f2. The target voltage is changed to Vp2 (> Vp1). In the following, the lower limit value of the minimum voltage required for the semiconductor integrated circuit 10 to stably operate at the target frequency f2 is referred to as the lower limit voltage Vl.

Here, if the target voltage Vp2 is set to a value substantially equal to the lower limit voltage Vl, the current flowing in the semiconductor integrated circuit 10 fluctuates due to noise generated in the semiconductor integrated circuit 10 due to the change in the operating frequency f. The supply voltage Vp may fall below the lower limit voltage Vl. Therefore, the power supply control circuit 14 sets the target voltage Vp2 to a value larger than the lower limit voltage Vl. That is, the target voltage Vp2 is
Vp2 = Vl + α
It must be set to the value represented by. Here, the value of α is determined in consideration of the fluctuation of the supply voltage Vp due to noise. However, if the supply voltage Vp larger than the lower limit voltage Vl is supplied to the semiconductor integrated circuit 10, the power consumption of the semiconductor integrated circuit 10 increases accordingly.

  Therefore, in the present embodiment, the semiconductor integrated circuit 10 operates in stages through one or more intermediate frequencies fm (f1 <fm <f2) by dividing the change from the initial frequency f1 to the target frequency f2 into a plurality of times. Change the frequency f. By so doing, voltage fluctuations caused by noise can be reduced, so that the value of α can be made smaller than when the initial frequency f1 is changed to the target frequency f2 at once.

  2A and 2B are diagrams for comparing the voltage control of the conventional example when the operating frequency f is changed with the voltage control of the present embodiment, and FIG. 2A shows the operating frequency f and the supply voltage Vp in the conventional example. FIG. 2B schematically shows temporal changes in the operating frequency f and the supply voltage Vp in this embodiment. In any of the figures, the horizontal axis represents time, and time t0 represents the change timing from the initial voltage Vp1 to the target voltage Vp2. The vertical axis indicates the magnitude of the supply voltage Vp and the operating frequency f. As shown in FIG. 2A, when the change from the initial frequency f1 to the target frequency f2 is performed at once, the supply voltage Vp fluctuates relatively greatly due to noise after the frequency change, and therefore the target voltage Vp2 is The supply voltage Vp after such fluctuation is a relatively large value so that it does not fall below the lower limit voltage Vl. On the other hand, in FIG. 2B, the change from the initial frequency f1 to the target frequency f2 is performed in three steps. That is, the operating frequency f is changed stepwise from the initial frequency f1 to the first intermediate frequency fm1, then from the first intermediate frequency fm1 to the second intermediate frequency fm2, and further from the second intermediate frequency fm2 to the target frequency f2. The In this way, in each of the plurality of changes, the ratio of the frequency after the change to the frequency before the change is relatively small compared to the case where the change is made at one time. The fluctuation of Vp is also reduced. Therefore, even if the target voltage Vp2 is lowered compared to the example of FIG. 2A, the supply voltage Vp can be prevented from falling below the lower limit voltage Vl.

  As apparent from FIG. 2B, in the present embodiment, the supply voltage Vp is first changed only once, and then the operating frequency f is changed a plurality of times. Generally, since the supply voltage Vp is changed by controlling the power supply circuit 13 outside the semiconductor integrated circuit 10, it takes time. On the other hand, since the change of the operating frequency f is internally performed by the semiconductor integrated circuit 10 itself, it does not require much time. In the present embodiment, although the number of changes of the operating frequency f is increased as compared with the conventional example, the number of times of change of the supply voltage Vp is one time, which is the same as that of the conventional example, so the time required for changing from the initial frequency f1 to the target frequency f2 Is almost the same as before. In the case where it does not take much time to change the supply voltage Vp, the supply voltage Vp may be changed stepwise in a plurality of times as the operating frequency f is changed stepwise.

  Here, when the change from the initial frequency f1 to the target frequency f2 is performed, how many times the change of the operating frequency f should be performed and how each of the one or more intermediate frequencies fm should be determined Will be described.

このような計算式によれば、半導体集積回路１０の動作周波数ｆは、初期周波数ｆ１から始まって（Ｎ−１）個の中間周波数ｆｍ（ｎ）を経て目標周波数ｆ２まで等比数列的に増加することになる。なお、実際には半導体集積回路１０で変更可能な動作周波数ｆの値には制約がある場合もあるが、そのときには変更可能な動作周波数ｆのうち上述した計算式で求められる値に近い値を設定すればよい。 Assuming that the number of changes in the operating frequency f when changing from a certain initial frequency f1 to a certain target frequency f2 is N, the semiconductor integrated circuit 10 passes the (N-1) intermediate frequencies fm through the operating frequency f. Will be changed. The intermediate frequency fm in this case should be determined so as to minimize the variation in the magnitude of noise generated by each change. Here, the magnitude of noise caused by one change is determined according to the ratio of the operating frequency f before and after the change. Therefore, when the intermediate frequency fm to be set in the nth change (n is a natural number from 1 to N-1) is expressed as fm (n), the intermediate frequency fm (n) is ideally calculated as Is required.

According to such a calculation formula, the operating frequency f of the semiconductor integrated circuit 10 starts from the initial frequency f1 and increases in a geometric sequence from (N−1) intermediate frequencies fm (n) to the target frequency f2. Will do. In practice, the value of the operating frequency f that can be changed by the semiconductor integrated circuit 10 may be limited, but at that time, a value close to the value obtained by the above-described calculation formula among the changeable operating frequencies f. You only have to set it.

When the intermediate frequency fm (n) is determined, a value to be set as the target voltage Vp2 is also determined accordingly. According to the calculation formula described above, the operating frequency f increases by (f2 / f1) ^{(1 / N)} times before the change in the change per time. The manufacturer of the electronic device 1 obtains information on how much voltage drop occurs with such a change in the operating frequency f by, for example, measuring using a prototype in advance. Can do. The target voltage Vp2 can be determined by determining the value of α using this information.

  Furthermore, how many times the change from the initial frequency f1 to the target frequency f2 should be performed can be determined as follows. FIG. 3 is a graph showing the relationship between the number of changes N when changing the operating frequency f from the initial frequency f1 to the target frequency f2, the required time R required for the change, and the target voltage Vp2. As shown in this figure, the total required time R required for changing the operating frequency f increases as the number of changes N increases. On the other hand, if the number of changes N is increased, the change width of the operating frequency f per operation can be reduced, so that the target voltage Vp2 can be lowered accordingly. However, as can be seen from the figure, when the number of changes N exceeds a certain level, the decrease rate of the target voltage Vp2 does not increase so much even if the number of changes N is further increased. Therefore, it is necessary to determine the number of changes N based on the balance between how low the target voltage Vp2 is to be suppressed and how long the required time R required for the change is to be kept. In the example of FIG. 3, a curve indicating the relationship between the number of changes N and the required time R and a curve indicating the relationship between the number of changes N and the target voltage Vp2 intersect in the vicinity of the number of changes = 3. . Therefore, when it is desired to achieve both the short required time R and the low target voltage Vp2, the number of changes N may be set to three. Alternatively, the number of times of change may be adopted with an emphasis on either the required time R or the target voltage Vp2.

  The values to be set as the target voltage Vp2 and the intermediate frequency fm need to be determined for each combination of the initial frequency f1 and the target frequency f2. These values may be recorded in advance in the semiconductor integrated circuit 10 when the electronic apparatus 1 is shipped from the factory. When the operating frequency f is changed from a certain initial frequency f1 to a certain target frequency f2, the semiconductor integrated circuit 10 sets the value of the target voltage Vp2 recorded in association with the combination of the initial frequency f1 and the target frequency f2. By outputting to the power supply control circuit 14, the power supply circuit 13 is requested to supply power at the target voltage Vp2. Thereafter, the semiconductor integrated circuit 10 is divided into N times so as to pass through the (N−1) intermediate frequencies fm recorded in association with the combination of the initial frequency f1 and the target frequency f2. Make changes. In this way, it is possible to reduce the target voltage Vp2 while suppressing the generation of noise accompanying the change of the operating frequency f.

  So far, the control for changing the operating frequency f has been described. From the viewpoint of lowering the supply voltage Vp in order to reduce power consumption, when changing the operating frequency f, it is not always necessary to change the operating frequency f in multiple steps as described above. However, not only the lower limit voltage Vl but also the upper limit voltage Vu corresponding to the operating frequency f may be set in the semiconductor integrated circuit 10. In this case, in order to operate the semiconductor integrated circuit 10 normally, it is necessary to prevent a voltage exceeding the upper limit voltage Vu from being applied. However, if the operating frequency f is greatly changed at once, the operating frequency f is changed. Due to the accompanying noise, the supply voltage Vp may temporarily exceed the upper limit voltage Vu. When the upper limit voltage Vu is a value that changes according to the operating frequency f, it is conceivable that the changed supply voltage Vp will exceed the upper limit voltage Vu even when changing the operating frequency f. Therefore, the semiconductor integrated circuit 10 may perform the change to the target frequency f2 in a plurality of times even when making a change to lower the operating frequency f. In this case, the number N of changes and the intermediate frequency fm may both be determined in the same manner as in the case of increasing the operating frequency f described above. Further, the target voltage Vp2 after the change is set to a value lower than the value expected as the fluctuation due to noise from the upper limit voltage Vu.

  In the above description, the power supply control circuit 14 controls the supply voltage Vp of the power supply circuit 13, but the semiconductor integrated circuit 10 may directly control the supply voltage Vp of the power supply circuit 13. Further, the temperature sensor 11 and the temperature controller 12 are not necessarily required only for performing the control for changing the operating frequency f described above.

[Voltage control according to temperature]
The power supply control circuit 14 may change the supply voltage Vp supplied from the power supply circuit 13 to the semiconductor integrated circuit 10 in accordance with the temperature change of the semiconductor integrated circuit 10 measured by the temperature sensor 11. In particular, in this embodiment, control is performed to lower the supply voltage Vp as the temperature of the semiconductor integrated circuit 10 increases. This will be described below.

  Due to the characteristics of the CMOS used in the semiconductor integrated circuit 10, the lower limit voltage Vl corresponding to the operating frequency f described above changes depending on the temperature T. FIG. 4 is a graph schematically showing the relationship between the lower limit voltage Vl and the temperature T. The broken line indicates the characteristics of a CMOS having a conventional gate length exceeding 65 nm, and the solid line indicates a CMOS having a recent gate length of 65 nm or less. The characteristics are shown respectively. Specifically, CMOS has temperature dependence on mobility and threshold voltage, which are parameters that determine its performance, and the mobility deteriorates as the temperature increases, and the performance improves as the threshold voltage increases. . The conventional CMOS having a gate length of more than 65 nm has a tendency to deteriorate at high temperatures because the influence of mobility is dominant. That is, as shown in FIG. 4, in the semiconductor integrated circuit having such a CMOS, even when the semiconductor integrated circuit operates at the same operating frequency, the lower limit voltage Vl rises when the temperature is higher than when the temperature is low. . Therefore, when a semiconductor integrated circuit including such a CMOS is used in a high temperature environment, it has been necessary to operate with a relatively high supply voltage Vp. However, in recent years, with the miniaturization of CMOS, the temperature dependence of the performance of CMOS has become different from the past. That is, the CMOS having a gate length of 65 nm or less that has recently appeared has a tendency that the influence of the threshold voltage is dominant at a high temperature, and the performance tends to be improved at a high temperature. For this reason, in such a semiconductor integrated circuit including a CMOS with a short gate length, the lower limit voltage Vl tends to decrease as the temperature increases, as shown in FIG.

  Therefore, the electronic apparatus 1 according to the present embodiment decreases the supply voltage Vp supplied to the semiconductor integrated circuit 10 as the temperature of the semiconductor integrated circuit 10 increases. Specifically, for example, when the temperature T of the semiconductor integrated circuit 10 indicated by the information output from the temperature controller 12 becomes equal to or higher than a predetermined threshold Tth, the power supply control circuit 14 decreases the supply voltage Vp by a predetermined decrease width β. The power supply circuit 13 is instructed. It is assumed that the value of β in this case is recorded in the power supply control circuit 14 in advance. Further, when the temperature T becomes lower than the predetermined threshold Tth, the power supply control circuit 14 returns the supply voltage Vp to the previous value (that is, increases the supply voltage Vp by β).

  FIG. 5 is a graph comparing the power consumption when such control is performed and when it is not performed. The horizontal axis indicates the temperature T, and the vertical axis indicates the power P. Further, the solid line indicates the case where the change control of the supply voltage Vp accompanying the temperature rise is not performed, and the broken line indicates the case where the change control is performed. In the example of this figure, the power supply circuit 13 reduces the supply voltage Vp by 0.5 V when the threshold Tth or higher, and as a result, the power consumption of the semiconductor integrated circuit 10 is greatly improved in the region where the temperature T is higher than the threshold Tth. I understand that

  In the example of FIG. 5, only one threshold value Tth is used. However, there may be a plurality of threshold values Tth. For example, when the threshold value Tth is set every 20 degrees, the power supply control circuit 14 decreases the supply voltage Vp step by step each time the temperature of the semiconductor integrated circuit 10 increases by 20 degrees. In this case, the decrease width β of the supply voltage Vp may be different from each other corresponding to each of the plurality of threshold values Tth. In this way, even if the lower limit voltage Vl changes non-linearly with respect to the rise in temperature T, the supply voltage Vp can be changed to an optimal value as the temperature T rises.

  Further, it is desirable that the value of β when the supply voltage Vp is lowered is set with a margin. For example, when the threshold value Tth is 50 ° C., the power supply control circuit 14 becomes equal to or higher than the lower limit voltage Vl when the temperature of the semiconductor integrated circuit 10 is (50−γ) degrees when the temperature T becomes 50 ° C. or higher. Thus, the supply voltage Vp is changed. The value of γ is determined according to the measurement error of the temperature sensor 11, for example. In this way, the power supply circuit 13 can supply a voltage necessary for the operation of the semiconductor integrated circuit 10 even if there is a measurement error of the temperature sensor 11 or the like. Further, when the power supply control circuit 14 detects that the temperature T has become equal to or higher than the threshold value Tth, the power supply control circuit 14 does not immediately change the supply voltage Vp but changes the supply voltage Vp after waiting for a predetermined time. Also good. Further, the power supply control circuit 14 may change the supply voltage Vp at a timing determined according to the operation state of the semiconductor integrated circuit 10. Specifically, when the processing load of the semiconductor integrated circuit 10 is less than a predetermined value, the temperature T tends not to increase so much, so that the supply voltage Vp is not immediately decreased even when the temperature T exceeds the threshold Tth. When the supply voltage Vp is lowered after a state where the temperature T is equal to or higher than the threshold value Tth continues for a predetermined time or longer, and conversely, when the temperature T becomes equal to or higher than the threshold value Tth, the processing load of the semiconductor integrated circuit 10 is higher than the predetermined value Alternatively, the supply voltage Vp may be immediately reduced.

  In the above description, the temperature sensor 11 is incorporated in the semiconductor integrated circuit 10 itself. However, the temperature sensor 11 may be arranged outside the semiconductor integrated circuit 10. In this case, the measurement accuracy of the temperature T is lower than when the temperature sensor 11 is disposed inside the semiconductor integrated circuit 10. However, if the measurement result of the temperature sensor 11 and the actual temperature of the semiconductor integrated circuit 10 are investigated in advance and the threshold value Tth and the decrease width β are determined according to the result, the temperature sensor 11 is arranged inside the semiconductor integrated circuit 10. As in the case where the temperature is increased, the control for lowering the supply voltage Vp according to the temperature rise of the semiconductor integrated circuit 10 can be realized.

  In the above description, the temperature controller 12 directly outputs information on the temperature T to the power supply control circuit 14. Instead, the temperature controller 12 sends information on the temperature T to the semiconductor integrated circuit 10. It is good also as outputting. In this case, the semiconductor integrated circuit 10 itself determines whether or not the temperature T is equal to or higher than the threshold Tth, and outputs a request for changing the supply voltage Vp to the power supply control circuit 14 according to the determination result.

  The control at the time of changing the operating frequency f and the control of the supply voltage Vp depending on the temperature described above may be performed independently or in combination with each other. In the case of combination, when the operating frequency f is changed, the supply voltage Vp after the change is determined by subtracting the decrease width β determined according to the temperature T at the time point from the target voltage Vp2 determined according to the target frequency f2 after the change. it can.

  DESCRIPTION OF SYMBOLS 1 Electronic device, 10 Semiconductor integrated circuit, 11 Temperature sensor, 12 Temperature controller, 13 Power supply circuit, 14 Power supply control circuit

Claims (4)

A power circuit;
A semiconductor integrated circuit that operates by a supply voltage supplied from the power supply circuit;
A temperature sensor for measuring the temperature of the semiconductor integrated circuit;
Including
The electronic device according to claim 1, wherein the power supply circuit lowers the supply voltage in accordance with an increase in the measured temperature. The electronic device according to claim 1,
The electronic device according to claim 1, wherein the power supply circuit lowers the supply voltage by a predetermined decrease amount when the measured temperature becomes a predetermined threshold value or more. A power circuit;
A semiconductor integrated circuit that operates by a supply voltage supplied from the power supply circuit;
A temperature sensor for measuring the temperature of the semiconductor integrated circuit;
A method for controlling an electronic device including:
Obtaining the measured temperature;
Reducing the supply voltage that the power supply circuit supplies to the semiconductor integrated circuit in response to the increase in the acquired temperature;
A method for controlling an electronic device, comprising: A semiconductor integrated circuit that operates by a supply voltage supplied from a power supply circuit,
A temperature sensor for measuring the temperature of the semiconductor integrated circuit;
Means for requesting the power supply circuit to lower the supply voltage in response to an increase in the measured temperature;
A semiconductor integrated circuit comprising:

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