Semiconductor Device and Wireless Tag Using the Same
First Claim
1. A semiconductor device comprising:
- a voltage detection circuit outputting a potential in accordance with a level of electric power supplied from an external portion;
a memory circuit holding a potential in accordance with a maximum value of the potential output from the voltage detection circuit; and
a protection circuit, wherein impedance of the protection circuit is changed in accordance with the potential which is held by the memory circuit.
1 Assignment
0 Petitions
Accused Products
Abstract
In a wireless tag with which a wireless communication system whose electric power of a carrier wave from a R/W is high, an overvoltage protection circuit is provided to prevent from generating excessive electric power in the wireless tag when the wireless tag receives excessive electric power. However, as noise is generated by operation of the overvoltage protection circuit, an error of reception occurs in receiving a signal whose modulation factor is small. To solve the problem, the maximum value of generated voltage in the wireless tag is held in a memory circuit after the overvoltage protection circuit operates, then the overvoltage protection circuit is controlled in accordance with the maximum value of generated voltage. The voltages at which the overvoltage protection circuit starts and stops operating are different from each other, and hysteresis occurs between the timing when the overvoltage protection circuit starts and stops operating.
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Citations
5 Claims
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1. A semiconductor device comprising:
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a voltage detection circuit outputting a potential in accordance with a level of electric power supplied from an external portion; a memory circuit holding a potential in accordance with a maximum value of the potential output from the voltage detection circuit; and a protection circuit, wherein impedance of the protection circuit is changed in accordance with the potential which is held by the memory circuit. - View Dependent Claims (4, 5)
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2. A semiconductor device comprising:
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a voltage detection circuit outputting a potential in accordance with a level of electric power supplied from an external portion; a memory circuit holding a potential in accordance with a maximum value of the potential output from the voltage detection circuit; and a protection circuit consuming or reflecting an excess of the electric power by changing impedance of the protection circuit in accordance with the potential which is held by the memory circuit.
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3. A semiconductor device comprising:
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an antenna circuit receiving electric power from an external portion; a voltage detection circuit outputting a potential in accordance with a level of the electric power; a memory circuit holding a potential in accordance with a maximum value of the potential output from the voltage detection circuit; and a protection circuit changing resonance frequency of the antenna circuit and reflecting an excess of the electric power by changing impedance of the protection circuit in accordance with the potential which is held by the memory circuit.
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Specification