JPH04307964A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To enable the design fully utilizing performance of an integrated circuit to improve the operation margin of a circuit for a wide range of temperature by selecting only one circuit from a plurality of reference voltage generating circuits depending on the signal from a temperature detecting circuit. CONSTITUTION:When ambient temperature is lower than the predetermined temperature T1, an output voltage of temperature detecting circuits 1a, 1b becomes lower than a threshold voltage of Schmitt trigger circuits 31a, 31b. As a result, only an output of an AND gate G1 becomes high level, a power supply voltage Vout which is equal to a voltage V1 generated by a reference voltage generating circuit 2a is supplied to a buffer circuit 4 and internal circuits 5 are driven by the lowest voltage. Meanwhile, when the ambient temperature is higher than the temperature T1 and is lower than the temperature T2, only output of gate G2 becomes high level and the circuit 5 is driven by an intermediate voltage. When the ambient temperature becomes higher than the temperature T2, only output of gate G3 becomes low level and the circuit 5 is driven by the highest voltage.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to semiconductor integrated circuit technology and to technology that is particularly effective when applied to countermeasures against temperature dependence of circuit characteristics, such as technology that is effective when applied to power supply voltage supply systems for logic integrated circuits. Regarding.

0002

2. Description of the Related Art The characteristics of semiconductor integrated circuits change depending on the environment in which they are used, particularly the temperature. Conventionally, regarding the temperature dependence of the characteristics of semiconductor integrated circuits, the worst-case conditions have been set for both the low-temperature side and the high-temperature side, and the design has been designed to operate correctly under those conditions, or a temperature compensation circuit has been provided for linear integrated circuits. (Asakura Shoten, June 1981, "Integrated Circuit Application Handbook," p. 118; Ohmsha, November 1984, edited by the Institute of Electronics and Communication Engineers, "LSI
(Refer to page 611 of ``Handbook.'')

0003

Conventionally, in the design of semiconductor logic integrated circuits, consideration has been given to reliability against temperature, but no consideration has been given to performance. For example, with regard to operating speed, the design takes into consideration the worst conditions on the high temperature side, and for finished products, the measurement speed on the high temperature side is only guaranteed as a specification. Therefore, even though it is possible to actually operate at a faster speed than the specified operating speed guaranteed at the low temperatures where it is actually used, the system has to be designed to operate at a slower speed. As a result, designs that take full advantage of the performance of integrated circuits have not been carried out. Furthermore, since the operating speed of the circuit changes depending on the temperature of the environment in which it is used, there is a problem in that if the system is configured to the limit of the specifications, the operating margin of the circuit will decrease when the temperature rises.

An object of the present invention is to enable a design that fully utilizes the performance of an integrated circuit, and to improve the operating margin of the circuit over a wide range of temperatures. The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0005]

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows. That is, for example, a temperature detection circuit, a plurality of reference voltage generation circuits generating different voltages from each other, and a signal for selecting one of the plurality of reference voltage generation circuits based on a signal from the temperature detection circuit are formed. A control circuit is also provided.

[0006]

[Operation] According to the above-described means, since the optimum reference voltage circuit is automatically selected according to the temperature of the environment in which the integrated circuit is used, it is possible to design a circuit that fully utilizes the performance of the integrated circuit. The above objective of improving the operating margin of the circuit over a wide range of temperatures can be achieved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a semiconductor integrated circuit according to the present invention. In FIG. 1, 1a and 1b are temperature detection circuits, 2a, 2b, and 2c are reference voltage generation circuits designed to generate different voltages, and 3 is a reference voltage generation circuit designed to generate different voltages. A control circuit for selecting one of the generated voltages among the reference voltage generation circuits 2a, 2b, and 2c; 4 is the reference voltage generation circuit 2;
The buffer circuit is, for example, a voltage follower or a power supply voltage generation circuit, which receives the generated voltage from one of the voltages a, 2b, and 2c and supplies the same voltage to the internal circuit 5 at low impedance.

The voltages V1, V2, V3 generated by the reference voltage generating circuits 2a, 2b, 2c are connected to the buffer circuit 4 via switches S1, S2, S3 which are controlled on and off by the control circuit 3. is configured to be supplied to The temperature detection circuits 1a and 1b include a pair of diodes D1 and D2 connected in parallel in opposite directions, and a resistor R connected in series with the diodes D1 and D2.
1 or R2, and the connection nodes between the two are output nodes N1 and N2, and are set so that R1>R2. As a result, when the same magnitude of through current is caused to flow, the potentials V1 and V of the output nodes N1 and N2 are
2 is configured such that V1>V2.

The control circuit 3 includes hysteresis circuits 31a and 31b such as Schmitt trigger circuits, inverters 33a and 33b that receive output signals from the hysteresis circuits 31a and 31b, and hysteresis circuits 31a and 31b and inverters 33a and 33b.
The output signal of is used as the input signal, and the switches S1, S2, S3
Selection signal C1, C2, C3 that turns on any one of
It is constituted by AND gates G1, G2, and G3 forming a .

In this embodiment, temperature detection circuits 1a and 1b
The temperature dependence of the characteristics of the diodes D1 and D2 is more remarkable than that of other elements (resistors and transistors), and the higher the ambient temperature, the more current flows through the diodes D1 and D2. Therefore, when the ambient temperature is lower than a certain predetermined temperature T1, the output voltages of the temperature detection circuits 1a and 1b are both lower than the threshold voltages of the Schmitt trigger circuits 31a and 31b, and this causes the Schmitt trigger circuits 31a and 31b to have lower threshold voltages. Both outputs of 31b are set to high level. As a result, only the output of the AND gate G1 is set to high level, the power supply voltage Vout which is the same as the voltage V1 generated by the reference voltage generation circuit 2a is supplied to the buffer circuit 4, and the internal circuit 5 is driven at the lowest voltage.

On the other hand, when the ambient temperature becomes higher than a certain predetermined temperature T1 (but lower than T2), both the output voltages of the temperature detection circuits 1a and 1b increase, and first only the output of the temperature detection circuit 1a becomes Schmitt trigger. Circuits 31a, 31
The voltage becomes higher than the threshold voltage of b, thereby causing the output of the Schmitt trigger circuit 31a to be at a low level (the output of the Schmitt trigger circuit 31b remains at a high level). As a result, only the output of AND gate G2 is set to high level, voltage V2 generated by reference voltage generating circuit 2b is supplied to buffer circuit 4, and internal circuit 5 is driven with an intermediate voltage.

Furthermore, when the ambient temperature becomes higher than a certain predetermined temperature T2, the output voltages of the temperature detection circuits 1a and 1b further increase, and the outputs of the temperature detection circuits 1a and 1b both exceed the Schmitt trigger circuits 31a and 31b. The voltage becomes higher than the threshold voltage, and thereby the outputs of Schmitt trigger circuits 31a and 31b are both set to low level. As a result, only the output of AND gate G3 is set to high level, voltage V3 generated by reference voltage generating circuit 2c is supplied to buffer circuit 4, and internal circuit 5 is driven at the highest voltage.

FIG. 2 shows the relationship between ambient temperature and supply voltage Vout in the above embodiment. As is clear from the figure, if this example is followed, the higher the ambient temperature, the higher the internal circuit will be driven at a higher voltage, so it will operate at almost the same speed over a wide temperature range, which will improve the performance of the integrated circuit. It becomes possible to design a system that takes full advantage of the Along with this, there is also the advantage that the device does not operate at an unnecessarily high speed at low temperatures, and power consumption is reduced by lowering the power supply voltage. On the other hand, since the internal circuitry is driven at a high voltage at high temperatures, there is an advantage that the operating speed does not decrease due to temperature rise, and the operating margin does not decrease even if the design is at the limit of the specifications.

Furthermore, in the above embodiment, since the output of the temperature detection circuit is received by the Schmitt trigger circuit, even if the output of the temperature detection circuit fluctuates due to temperature fluctuations, the power supply voltage Vout to the internal circuit can be maintained. It can be stably supplied.

Note that in the above embodiment, the reference voltage generation circuit 2
Switches S1, S2, and S3 are provided to select one of the generated voltages V1, V2, and V3 of a, 2b, and 2c. The reference voltage generation circuit 2a, 2b, or 2c is configured to activate one of the reference voltage generation circuits 2a, 2b, and 2c by selectively turning on a power switch provided therein or a switch provided on the current path. Good too. Alternatively, the voltage itself can be changed by changing element constants such as resistances provided in the reference voltage generating circuit according to signals from the control circuit.

Furthermore, in the above embodiment, a plurality of temperature detection circuits 1a and 1b whose output voltages change depending on the ambient temperature are provided, and their output voltages are input to Schmitt trigger circuits 31a and 31b having the same threshold voltage. Although,
It is also possible to provide only one temperature detection circuit whose output voltage changes depending on the ambient temperature and supply the output voltage to a plurality of Schmitt trigger circuits configured to have different threshold voltages.

Furthermore, in the above embodiment, the reference voltage generation circuit is switched between high temperature and low temperature, but in a semiconductor integrated circuit having a delay circuit, it is possible to use a plurality of delay circuits with different time constants or switch the time constant. A delay circuit may be provided, and the circuit or time constant may be switched between high temperature and low temperature. Also, M.O.
In the S integrated circuit, a plurality of circuits of the same type, differing only in the constants of the MOSFETs constituting the circuit, may be provided, and the circuits may be switched between high temperature and low temperature.

As explained above, the above embodiment includes a temperature detection circuit, a plurality of reference voltage generation circuits that generate different voltages from each other, and a plurality of reference voltage generation circuits that generate voltages based on signals from the temperature detection circuit. Since a control circuit is provided to form a signal to select one of the reference voltage circuits, the optimum reference voltage circuit is automatically selected according to the temperature of the environment in which the integrated circuit is used. This has the effect of not only making it possible to design a device that takes full advantage of its performance, but also improving the operating margin of the circuit over a wide range of temperatures.

Although the invention made by the present inventor has been specifically explained above based on examples, the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Needless to say. For example, in the above embodiment, a temperature detection circuit in which a diode and a resistor formed on the same chip as the internal circuit are connected in series is used, but other types of circuits may be used or a varistor may be used instead of the diode. It is also possible to use other elements with significant temperature dependence, such as a thermistor, or to configure the temperature detection circuit with an external circuit. However, if a diode is used, it can be easily formed in the same process as other circuit elements, resulting in good process consistency.

In the above explanation, the invention made by the present inventor was mainly applied to the logic integrated circuit RAM, which is the background field of application, but the invention is not limited thereto, and is applicable to linear It can be used for integrated circuits and other semiconductor integrated circuits in general.

[0021]

Effects of the Invention The effects obtained by typical inventions disclosed in this application are briefly explained below. That is, it is possible to design a circuit that fully utilizes the performance of the integrated circuit, and to improve the operating margin of the circuit over a wide range of temperatures.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of a semiconductor integrated circuit according to the present invention.

FIG. 2 is a graph showing the relationship between ambient temperature and output voltage of the circuit of the example.

[Explanation of symbols]

1a, 1b Temperature detection circuit 2a, 2b, 2c Reference voltage generation circuit 3 Control circuit 4 Buffer circuit 31a, 31b Hysteresis circuit (Schmitt trigger circuit)

Claims (3)

[Claims] 1. A control circuit comprising: a plurality of circuits having the same function having different characteristics; and a control circuit forming a signal for selecting one of the plurality of circuits with the same function based on a signal from a temperature detection circuit. A semiconductor integrated circuit characterized by: 2. A temperature detection circuit, a plurality of reference voltage generation circuits generating different voltages from each other, and a signal for selecting one of the plurality of reference voltage generation circuits based on a signal from the temperature detection circuit. 1. A semiconductor integrated circuit comprising: a control circuit for forming a semiconductor integrated circuit; 3. The semiconductor integrated circuit according to claim 1, wherein the control circuit includes a hysteresis circuit for identifying a signal from the temperature detection circuit.