Electric power consumption reduction device
First Claim
1. A semiconductor device which can change a power voltage of at least part of said semiconductor device, comprising:
- a constant-voltage circuit for generating said power voltage, which comprises voltage generation means for generating at least first, second, and third voltages, wherein the absolute value of said first voltage is set to be less than the absolute value of said second voltage, andthe absolute value of said second voltage is set to be less than the absolute value of said third voltage, wherein;
said constant-voltage circuit further comprises control means for said voltage generation means such that, when switching from said first voltage to said third voltage, or from said third voltage to said first voltage is performed, said second voltage is generated before said switching to said first or third voltage is performed, thus implementing stepwise voltage switching.
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Accused Products
Abstract
A semiconductor device, microcomputer, or electronic equipment capable of switching internal power voltages in order to suppress the power consumption thereof can prevent erroneous operation of the internal circuitry by switching the level of the internal power voltage in a stepwise manner. A constant-voltage circuit that causes the generation of power voltages is capable of generating voltages of at least three levels. During the switching of the power voltages, a control circuit implements stepwise switching of the power voltages by causing the sequential output of the voltages in increasing or decreasing order of absolute value. Immediately after a switch of power voltage, the level of the signal on the signal line is determined to be at the same level as that before the switching even if a potential change in a signal line is delayed by more than a change in the threshold voltage of a digital circuit, and thus erroneous recognition of data, or rather data inversion, is prevented. This improves the reliability of the device.
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Citations
26 Claims
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1. A semiconductor device which can change a power voltage of at least part of said semiconductor device, comprising:
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a constant-voltage circuit for generating said power voltage, which comprises voltage generation means for generating at least first, second, and third voltages, wherein the absolute value of said first voltage is set to be less than the absolute value of said second voltage, and the absolute value of said second voltage is set to be less than the absolute value of said third voltage, wherein; said constant-voltage circuit further comprises control means for said voltage generation means such that, when switching from said first voltage to said third voltage, or from said third voltage to said first voltage is performed, said second voltage is generated before said switching to said first or third voltage is performed, thus implementing stepwise voltage switching. - View Dependent Claims (2, 3)
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4. A semiconductor device for selecting and using as the power voltage thereof a first power voltage and a second power voltage of an absolute value less than that of said first power voltage, comprising:
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a voltage generation circuit for generating said first power voltage, said second power voltage, and a constant voltage of a potential intermediate between those of said first power voltage and said second power voltage; and first and second gate circuits mutually connected by signal transmission paths and each capable of operating equally well under said first power voltage and said second power voltage;
whereinduring a switching of power voltage to said first and second gate circuits from said first power voltage to said second power voltage or from said second power voltage to said first power voltage, a stepwise switching of power voltage is performed by generating the constant voltage of intermediate potential before switching to said first or second power voltage. - View Dependent Claims (5, 6, 7)
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8. A microcomputer comprising:
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a clock output circuit for outputting a first clock and a second clock of a frequency lower than that of said first clock; a central processing unit (CPU) operating by using either of said first and second clocks output by said clock output circuit; a voltage generation circuit for generating a first power voltage, a second power voltage of an absolute value less than that of said first power voltage, and a constant voltage of a potential intermediate between those of said first power voltage and said second power voltage; and a control circuit for controlling operation of said voltage generation circuit;
wherein;said control circuit controls operation of said voltage generation circuit in such a manner that stepwise switching of a power voltage occurs such that, when said CPU is operating using said first clock, said first power voltage is generated from said voltage generation circuit;
when said CPU is operating using said second clock, said second power voltage is generated from said voltage generation circuit; and
when switching between said first power voltage and said second power voltage is being performed, said constant voltage of intermediate potential is first generated before switching to said first or second power voltage. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A microcomputer comprising:
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a clock output circuit provided with a first oscillation circuit for generating a first clock, a second oscillation circuit for generating a second clock of a frequency lower than that of said first clock, and a clock selection circuit for selecting and outputting said first or second clock on the reception of a clock select signal; a central processing unit (CPU) operating by using said first or second clock output by said clock output circuit; a voltage generation circuit for generating a first power voltage for operations using said first clock, a second power voltage of an absolute value less than that of said first power voltage for operations using said second clock, and a constant voltage of a potential intermediate between those of said first power voltage and said second power voltage; and a control circuit for providing control such that, on receiving an instruction from said CPU indicating that clock-switching is to be performed, said control circuit generates a control signal for said voltage generation circuit and said clock select signal, and causes stepwise switching of said power voltage and clock switching by applying said signals to said voltage generation circuit and said clock selection circuit, respectively. - View Dependent Claims (15, 16, 17, 18)
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19. An electronic equipment including a semiconductor device which can change a power voltage of at least part of the semiconductor device, comprising:
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a constant-voltage circuit for generating said power voltage, which comprises voltage generation means for generating at least first, second, and third voltages, wherein the absolute value of the first voltage is set to be less than the absolute value of the second voltage, and the absolute value of the second voltage is set to be less than the absolute value of the third voltage, wherein; the constant-voltage circuit further comprises control means for the voltage generation means such that, when switching from the first voltage to the third voltage, or from the third voltage to the first voltage is performed, the second voltage is generated before the switching to the first or third voltage is performed, thus implementing stepwise voltage switching. - View Dependent Claims (20, 21, 22)
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23. An electric equipment including a microcomputer, comprising:
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a clock output circuit for outputting a first clock and a second clock of a frequency lower than that of the first clock; a central processing unit (CPU) operating by using either of the first and second clocks output by the clock output circuit; a voltage generation circuit for generating a first power voltage, a second power voltage of an absolute value less than that of the first power voltage, and a constant voltage of a potential intermediate between those of the first power voltage and the second power voltage; and a control circuit for controlling operation of the voltage generation circuit, wherein; the control circuit controls operation of the voltage generation circuit in such a manner that stepwise switching of a power voltage occurs such that, when the CPU is operating using the first clock, the first power voltage is generated from the voltage generation circuit;
when the CPU is operating using the second clock, the second power voltage is generated from the voltage generation circuit; and
when switching between the first power voltage and the second power voltage is being performed, the constant voltage of intermediate potential is first generated before switching to the first or second power voltage. - View Dependent Claims (24, 25, 26)
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Specification