JP2005165511A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an illicit action to a device with a simple configuration. <P>SOLUTION: A semiconductor device 3 including a rectifier 4 which rectifies received power and a regulator 6 which stabilizes rectified power output to supply to inner circuits, is equipped with voltage divider circuits 5 and 7 which divide the output of the rectifier 4 and the regulator 6 respectively, and a comparator 8 which compares the output of the voltage divider circuits 5 and 7 mutually. Further, it has a mode control means to control an operation mode based on the output of the comparator 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor device that protects confidential information inside the device from fraudulent acts for the purpose of falsification and copying.

  In recent years, in the field of IC cards such as cash cards and credit cards, confidentiality of confidential information inside semiconductor devices has become very important. In order to protect this confidentiality, various sensor circuits are provided in the semiconductor device, and when an input or condition that is different from normal operation is detected, technology that prevents tampering and reading of confidential information has become important. . One of them is a technology in which a voltage detection circuit is mounted in a card body, and when a voltage other than the operation guarantee is applied, a malfunction of the semiconductor device is induced to prevent information from being estimated and analyzed.

FIG. 2 is a diagram showing a configuration of a voltage detection circuit mounted on the semiconductor device. In FIG. 2, the voltage detection circuit includes a voltage dividing circuit 20 that divides a power supply voltage to be monitored to generate a comparison voltage, a reference voltage generation circuit 21 for comparison, and a comparator 22. In this voltage detection circuit, the voltage obtained by dividing the power supply voltage by the voltage dividing circuit 20 and the voltage generated by the reference voltage generating circuit 21 are compared by the comparator 22, and the fraud detection signal C is output according to the comparison result. (For example, refer to Patent Document 1). Further, by using the fraud detection signal C, it is possible to prevent the information from being plagiarized and analyzed by inducing a malfunction of the semiconductor device, for example.
JP-A-10-117138

  However, the conventional fraud detection technique requires a complicated voltage detection circuit including the reference voltage generation circuit 21 in the card body, and a temporary voltage change due to a steep environmental change and a voltage change due to fraudulent behavior. Difficult to distinguish. On the other hand, if it is attempted to employ a circuit that is not affected by variations in device characteristics and environmental changes, more complicated compensation circuits and trimming circuits are required, which increases design difficulty and requires a layout area for these circuits.

  On the other hand, when a simple voltage detection circuit is used, it is necessary to impose a certain allowable range on the detector, and there is a possibility that an illegal act is performed using the allowable range. Further, if the circuit is not affected by device characteristic fluctuations or environmental changes, more complicated compensation circuits and trimming circuits are required, which is uneconomical. An object of the present invention is to provide a semiconductor device capable of detecting an illegal act against the device with a simple configuration.

  The semiconductor device of the present invention is a semiconductor device including a rectifying unit that rectifies received power and a stabilizing unit that stabilizes a rectified output and supplies the rectified output to an internal circuit, and outputs the rectifying unit and the stabilizing unit. Each of the voltage dividing means for dividing the pressure and a comparing means for comparing the outputs of the voltage dividing means. According to this configuration, by providing the comparison unit that compares the divided voltage outputs of the rectification unit and the stabilization unit with each other, it is possible to detect a potential change at the time of fraud that changes with respect to normal operation. It is possible to detect fraud by capturing.

  The semiconductor device having the above configuration converts the power that can be used in the semiconductor device by the rectifying means, stabilizes the power by the stabilizing means, and supplies the power to the internal circuit. During normal operation, the output potential of the rectifying means is greater than the output potential of the stabilizing means. However, if a fraudulent act of applying a voltage directly to the output of the stabilization means using an external pad or the like is performed, the output potential of the stabilization means is less than the output potential of the rectification means because the rectification means is not used. Also grows. By detecting such a potential change by the comparison means, it is possible to detect an illegal act with a simple configuration.

  The semiconductor device of the present invention further includes mode control means for controlling an operation mode based on the output of the comparison means. According to this configuration, by including mode control means for controlling the operation mode based on the output of the comparison means, a fixed mode that does not return unless the power is turned off at the time of fraud, a safety mode that erases confidential information, etc. It is possible to control to shift to, and to prevent leakage of confidential information inside at the time of fraud.

  According to the present invention, it is possible to detect a change in potential during a fraud that changes with respect to normal operation with a simple configuration, and it is possible to detect a fraud by capturing this potential change. Further, by controlling the operation mode when an illegal act is detected, leakage of confidential information inside can be prevented and tamper resistance can be improved.

  FIG. 1 is a diagram showing a configuration of a semiconductor device according to an embodiment of the present invention. The semiconductor device shown in FIG. 1 is mounted on an IC card or the like, and includes a receiving antenna 2, a rectifier 4, a first voltage dividing circuit 5, a regulator 6, a second voltage dividing circuit 7, a comparator 8, an internal circuit load 9, and a wafer. A test pad 10 and a control circuit 11 are provided.

  The reception antenna 2 receives a carrier transmitted through the transmission antenna 1 of an external reader / writer. The rectifier 4 rectifies the carrier received by the receiving antenna 2 and extracts a DC voltage. The regulator 6 suppresses fluctuations in the voltage obtained from the rectifier 2 and supplies a stabilized voltage to the internal circuit load 9 and the like. The voltage dividing circuits 5 and 7 are respectively connected to the input side and the output side of the regulator 6, and the input side voltage and the output side voltage are stabilized from the regulator 6 by the resistance elements R1, R2, R3, and R4. Divide the voltage to a voltage sufficiently lower than the applied voltage.

  The comparator 8 receives the voltages divided by the two voltage dividing circuits 5 and 7, compares their magnitudes, and outputs a fraud detection signal described later. The fraud detection signal output from the comparator 8 functions to control the semiconductor device 3 to shift to a fixed mode that does not return unless the power is turned off, or to a safe mode that erases confidential information. The test pad 10 is used to input a test signal to an internal circuit load 9 having a memory that is a circuit to be tested and a CPU that manages the memory. The control circuit 11 supplies a control signal for invalidating the comparison operation by the comparator 8 only when the internal circuit load 9 is in the test mode.

  In the above configuration, when the semiconductor device 3 is inspected, the semiconductor device is set to the test mode by the mode selection signal D. Upon receiving the mode selection signal D, the control circuit 11 outputs a control signal, invalidates the comparison operation by the comparator 8, and outputs a normal detection signal instead of the fraud detection signal C. Further, inspection is performed by supplying power from the inspection PAD 10 to the internal circuit load 9 and the like of the semiconductor device 3. In modes other than the test mode, the comparison operation of the comparator 8 is always enabled by a control signal from the control circuit 11.

  On the other hand, when a carrier is transmitted from the transmitting antenna 1 of the reader / writer, the receiving antenna 2 in the IC card receives the carrier and propagates it to the semiconductor device 3. The rectifier 3 rectifies the propagated carrier and takes out DC power at a level suitable for the subsequent circuits. However, the power at this point is unstable and the voltage fluctuates up and down depending on the communication distance of the carrier. The regulator 6 creates a stable voltage according to the specifications of the semiconductor device from the unstable voltage and supplies it to the internal circuit load 9 of the semiconductor device 3.

  Usually, there is a level difference between the output voltage of the rectifier 4 (input voltage of the regulator 6) and the output voltage of the regulator 6, and the potential of the output voltage of the rectifier 4 is higher. Since the comparator 8 obtains the drive voltage from the regulator 6, for comparison, the first voltage dividing circuit 5 and the second voltage dividing circuit 7 are used to make the voltage lower than the voltage of the regulator 6 at the same ratio. It is more convenient in terms of operation to generate the reduced comparison voltages A and B and input them to the comparator 8. Thereby, the comparator 8 monitors the relationship that the comparison voltage A is higher in potential than the comparison voltage B.

  On the other hand, the fraudster disassembles the IC card and attacks the semiconductor device itself by applying various voltages from the outside using the inspection pad 10 to alter the confidential information or information from the inside of the semiconductor device. Try to estimate. For this reason, the carrier by the correct communication is not input via the rectifier 3, and the magnitude relationship between the comparison voltages A and B is reversed. Accordingly, the fraud detection signal C is output from the comparator 8, and based on the fraud detection signal, the fixed mode, the operation reset, or the means for shifting the operation mode so as to erase the confidential information is provided. Can be protected. Furthermore, if there is a function of switching the mode selection signal D physically rather than electrically, the tamper resistance is further improved.

  The semiconductor device of the present invention can detect a potential change at the time of fraud that changes with respect to normal operation with a simple configuration, and can detect the fraud by capturing this potential change. It is useful as a semiconductor device or the like that protects confidential information inside the device from unauthorized acts for the purpose of falsification and copying.

It is a figure showing composition of a semiconductor device concerning one embodiment of the present invention. It is a figure which shows the structure of the conventional voltage detection circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission antenna 2 Reception antenna 3 Semiconductor device 4 Rectifier 5 1st voltage dividing circuit 6 Regulator 7 2nd voltage dividing circuit 8 Comparator 9 Internal circuit load 10 Test pad 11 Control circuit 20 Voltage dividing circuit 21 Reference voltage generation circuit 22 Comparator A, B Comparison voltage C Fraud detection signal D Mode selection signal

Claims (2)

A semiconductor device including rectifying means for rectifying received power and stabilizing means for stabilizing a rectified output and supplying the rectified output to an internal circuit,
Voltage dividing means for dividing the output of the rectifying means and the stabilizing means, respectively;
A semiconductor device comprising comparison means for comparing outputs of the voltage dividing means with each other.   2. The semiconductor device according to claim 1, further comprising mode control means for controlling an operation mode based on an output of the comparison means.

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