Semiconductor integrated circuit device

• US 8,138,893 B2
• Filed: 03/28/2008
• Issued: 03/20/2012
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: Tsukamoto, Takayuki, Endo, Takefumi
• Primary Examiner(s): HOLLOWAY III, EDWIN C
• Application Number:
  US12/057,671
• Publication Number:
  US 20080238632A1
• Time in Patent Office: 1,453 Days
• Field of Search: 340/10.1, 340/10.5, 340/572.1, 340/572.3, 342/44, 342/51, 235/492
• US Class Current: 340/10.5
• 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 greater than or equal to a predetermined arbitrary field intensity. If the power is less 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, the communication distance limitation control circuit comprising;

a communication distance setting unit storing communication distance limitation setting data for setting the limitation of the communication distance with the reader/writer; and

a power intensity monitor unit monitoring power of the primary voltage generated by the rectification circuit and making a judgment as to whether or not the power of the primary voltage is greater than or equal to a predetermined field intensity,

wherein the communication distance limitation control circuit performs control so that;

(1) the command decode unit receives an input of the digital signal outputted from the command demodulation circuit by making a connection between the command demodulation circuit and the command decode unit conductive when the communication distance limitation setting data is not set in the communication distance setting unit,

(2) the command decode unit receives the input of the digital signal outputted from the command demodulation circuit by making the connection between the command demodulation circuit and the command decode unit conductive when the communication distance limitation setting data is set in the communication distance setting unit and the power intensity monitor unit makes judgment that the power of the primary voltage is greater than or equal to the predetermined field intensity, and

(3) the command decode unit receives no input of the digital signal outputted from the command demodulation circuit by making the connection between the command demodulation circuit and the command decode unit nonconductive when the communication distance limitation setting data is set in the communication distance setting unit and the power intensity monitor unit makes iudgment that the power of the primary voltage is less than the predetermined field intensity.

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

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.

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

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.

4. 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 performing operation and outputting a result of the operation to the back scatter circuit and including a command decode unit receiving a signal from the command demodulation circuit,

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

wherein the logic circuit couples a signal path from the command demodulation circuit to the command decode unit when the state management unit makes judgment that the current state is in the ordinary communication,

wherein the logic circuit couples the signal path from the command demodulation circuit to the command decode unit when the state management unit makes judgment that the current state is in the distance limitation communication and the field intensity detected by the power intensity monitor unit is greater than or equal to a predetermined field intensity, and

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

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

wherein the state management unit comprises a register for setting communication distance limitation setting data for setting the limitation of the communication distance with the reader/writer;

wherein the current state is in the ordinary communication when the communication distance limitation setting data is not set in the register,

wherein the current state is in the distance limitation communication when the communication distance limitation setting data is set in the register.

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

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.

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

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.

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