Semiconductor Device and Wireless Tag Using the Same

• US 20100072285A1
• Filed: 09/11/2009
• Published: 03/25/2010
• Est. Priority Date: 09/19/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Nishijima, Tatsuji
• Granted Patent: US 8,439,270 B2
• Time in Patent Office: Days
• US Class Current: 235/492
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: H01L 27/0251 for MOS devices

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.

Claims

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.

4. The semiconductor device according to any one of claims 1 to 3,

wherein the memory circuit includes a reset terminal, and

the memory circuit resets the potential which is held when a reset signal is input to the reset terminal.

5. A wireless tag comprising:

the semiconductor device according to any one of claims 1 to 3;

a wireless communication circuit by which communication with an external portion can be performed wirelessly;

a power supply circuit which generates a DC voltage based on the electric power supplied from the external portion; and

a logic circuit which is driven by using the generated DC voltage and performs data processing.

2. 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 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.

3. A semiconductor device comprising:

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.