SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE

• US 20080238632A1
• Filed: 03/28/2008
• Published: 10/02/2008
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: ENDO, Takefumi, Tsukamoto, Takayuki
• Granted Patent: US 8,138,893 B2
• Time in Patent Office: Days
• US Class Current: 340/10.51
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

In an IC tag, when a semiconductor integrated circuit device is activated, an operation control unit sets existence/nonexistence of a communication distance limitation for reducing a communication distance to a state management unit. If the communication distance limitation is not set, a switch unit is turned ON and a demodulated command is inputted from a command demodulation circuit to a command decode unit. If the communication distance limitation is set, a power intensity monitor unit judges whether the power of a rectification circuit is a predetermined arbitrary field intensity or more. If the power is smaller than the predetermined arbitrary field intensity, the switch unit is turned OFF and various commands demodulated by the command demodulation circuit are not inputted to the command decode unit. As a result, the semiconductor integrated circuit device does not operate.

Claims

1. A semiconductor integrated circuit device used in an IC tag converting a radio wave received from a reader/writer to power and returning information to the reader/writer comprising:

a rectification circuit receiving the radio wave outputted from the reader/writer, rectifying power caused by electromagnetic induction of the radio wave and generating a primary voltage;

a voltage stabilization circuit stabilizing the primary voltage generated by the rectification circuit and generating an internal power source voltage;

a command demodulation circuit demodulating a command added to the radio wave outputted from the reader/writer to a digital signal;

a command decode unit decoding the command of the digital signal demodulated by the command demodulation circuit; and

a communication distance limitation control circuit limiting a communication distance with the reader/writer,

wherein the communication distance limitation control circuit performs control permitting no acceptance of the digital signal outputted from the command demodulation circuit when communication distance limitation setting data setting limitation of the communication distance with the reader/writer is set.

2. The semiconductor integrated circuit device according to claim 1,

wherein the communication distance limitation control circuit comprises:

a communication distance setting unit storing information about whether the communication distance limitation setting data setting the limitation of the communication distance with the reader/writer is set;

a power intensity monitor unit monitoring power of the primary voltage generated by the rectification circuit and making judgment whether the power of the primary voltage is predetermined arbitrary field intensity or more; and

a communication distance limitation circuit performing control so that the command decode unit has no input of the digital signal outputted from the command demodulation circuit by making connection between the command demodulation circuit and the command decode unit nonconductive when the communication distance limitation setting data setting the limitation of the communication distance is set in the communication distance setting unit and the power intensity monitor unit makes judgment that the power of the primary voltage is smaller than the predetermined arbitrary field intensity.

3. The semiconductor integrated circuit device according to claim 1,

wherein the communication distance limitation control circuit comprises:

a communication distance setting unit storing information about whether the communication distance limitation setting data setting the limitation of the communication distance with the reader/writer is set;

a power intensity monitor unit monitoring power of the primary voltage generated by the rectification circuit and making judgment whether the power of the primary voltage is predetermined arbitrary field intensity or more; and

a communication distance limitation circuit shutting off the radio wave from the reader/writer inputted to the command demodulation circuit when the communication distance limitation setting data setting the limitation of the communication distance is set in the communication distance setting unit and the power intensity monitor unit makes judgment that the power of the primary voltage is smaller than the predetermined arbitrary field intensity.

4. The semiconductor integrated circuit device according to claim 2,

wherein the power intensity monitor unit monitors the power of the primary voltage using a clamp current clamped when the voltage stabilization circuit generates the internal power source voltage.

5. The semiconductor integrated circuit device according to claim 2,

wherein the power intensity monitor unit performs comparison between a clamp voltage obtained by converting a clamp current to a voltage and a comparison voltage and outputs a result of the comparison as a judgment result.

6. A semiconductor integrated circuit device including a rectification circuit connected to an external antenna, a command demodulation circuit and a back scatter circuit, comprising:

a voltage stabilization circuit stabilizing a voltage of the rectification circuit and supplying power;

a power intensity monitor unit detecting field intensity from an output voltage of the voltage stabilization circuit; and

a logic circuit receiving a signal from the command demodulation circuit, performing operation and outputting a result of the operation to the back scatter circuit,

wherein the logic circuit comprises a state management unit making judgment whether a current state is ordinary communication or under distance limitation, and

wherein the logic circuit cuts off a signal path from the command demodulation circuit to a command decode unit when the state management unit makes judgment that the current state is under the distance limitation and the field intensity detected by the power intensity monitor unit is smaller than predetermined arbitrary field intensity.

7. The semiconductor integrated circuit device according to claim 6,

wherein the logic circuit further comprises a communication distance limitation control circuit including a communication distance limitation circuit performing control so that the command decode unit has no input of a digital signal outputted from the command demodulation circuit by making connection between the command demodulation circuit and the command decode unit nonconductive when the state management unit makes judgment that the current state is under the distance limitation and the field intensity detected by the power intensity monitor unit is smaller than the predetermined arbitrary field intensity.

8. The semiconductor integrated circuit device according to claim 6,

wherein the power intensity monitor unit monitors power of a primary voltage generated by the rectification circuit and makes judgment whether the power of the primary voltage is the predetermined arbitrary field intensity or more.

9. The semiconductor integrated circuit device according to claim 8,

wherein the power intensity monitor unit monitors the power of the primary voltage using a clamp current clamped when the voltage stabilization circuit generates an internal power source voltage.

10. The semiconductor integrated circuit device according to claim 8,

wherein the power intensity monitor unit performs comparison between a clamp voltage obtained by converting a clamp current to a voltage and a comparison voltage and outputs a result of the comparison as a judgment result.