JP3546979B2 - Semiconductor device and IC card device using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device having a built-in oscillation circuit and an IC card device using the same, and more particularly to a circuit configuration of the oscillation circuit.
[0002]
[Prior art]
Conventionally, there is a so-called CR oscillation circuit or a ring oscillation circuit as an oscillation circuit which does not require components such as a vibrator such as a ceramic crystal or an inductance element and has a simple circuit configuration and is easily integrated, and these are formed in the semiconductor device. It was often used. The ring oscillating circuit 9 shown in FIG. 4 is an example, and each input and output of a signal inverting element 9m (m = 1 to n: n is a positive odd number) composed of a NAND circuit, an inverter circuit and the like formed in a CMOS configuration is connected to a ring. An odd number of the capacitors are connected in cascade, and a delay capacitor 3m is connected to the output of the signal inverting element 9m. Further, a signal connected to one input of the NAND 9 from the inverter 9n is also connected to an input of the inverter 6, and an output thereof is connected to another circuit (not shown) as a clock signal CP so that it can be used as a reference clock of the semiconductor device. And a control signal S is connected to the other input of the NAND 91 so that the start and stop of the oscillation can be controlled.
[0003]
[Problems to be solved by the invention]
However, the above-described ring oscillation circuit and CR oscillation circuit can be used without any problem in the case of a device such as a toy that does not require high precision in the oscillation frequency, but a ticket gate system using a non-contact type IC card. It was difficult to use this device for the following reasons.
[0004]
That is, in a ticket gate system using a non-contact type IC card, it is necessary to match the timing of data transmission and reception between the IC card and the ticket gate, and relatively high precision oscillation characteristics are required. Since only the power that receives and rectifies the transmitted radio waves from the ticket gate and charges the capacitor is used as the power source, the power supply voltage supplied to the oscillation circuit is likely to fluctuate depending on the distance from the ticket gate and the reception state, and the power supply voltage As a result, the driving capability of each signal inverting element changes and the charging / discharging current of each capacitor changes, so that the delay time of each signal inverting element changes and the oscillation frequency fluctuates. Similarly, the driving capability of each output inverting element is also likely to change due to a temperature change or a variation in element characteristics at the time of manufacturing a semiconductor device, and the oscillation frequency has further changed.
[0005]
As described above, the oscillation frequency fluctuates due to various factors.Conventionally, the center oscillation frequency is adjusted by changing the size and number of transistors of the signal inversion element or changing the capacitance value by changing the capacitor size. However, these changes are time-consuming and impractical because a mask or the like used in forming a semiconductor device must be changed.
[0006]
In addition, since there was no method for suppressing the fluctuation of the oscillation frequency of the oscillation circuit built in the conventional semiconductor device, the required frequency accuracy could not be satisfied unless the conditions such as the power supply voltage and the temperature were limited. .
The frequency accuracy can be easily improved by using an external component such as an oscillator. However, in the case of an IC card or the like, the product thickness is limited, and the board area for externally mounting the component is limited. However, adoption was difficult because of the increased size, the need for a package with more pins, and the need for additional external component costs and management costs, which increased costs.
[0007]
Therefore, the present invention provides an oscillation circuit in which the frequency accuracy of an oscillation frequency is relatively good in a wide power supply voltage range and a temperature range and in which a reference oscillation frequency can be easily changed inside a semiconductor device. It is an object to easily provide a semiconductor device having a small number of components.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an IC card device according to claim 1 includes a ring-shaped odd number of a plurality of signal inverting elements as an oscillation circuit of a non-contact type IC card which rectifies a received signal and uses it as a power supply. An IC card device using a semiconductor device incorporating a ring oscillation circuit connected in cascade ,
At least one of in series with the constant current circuit is set to less current value than the current capacity of the power supply side transistors of the power supply side transistor connected to the power supply voltage or reference potential of the transistors constituting the plurality of signal inversion element characterized by a transistor are respectively connected.
[0009]
By using the oscillation circuit of the circuit configuration of the present invention to an IC card system, power by Rukoto suppressing fluctuation of the delay time of the voltage and the signal inverting element of the oscillation circuit when the temperature is varied little in the oscillation frequency variation This makes it possible to easily form an oscillator that prevents an increase in current consumption while reducing the number of external components.
[0010]
Embodiment
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. In this specification, the same or similar circuit elements are denoted by the same reference numerals throughout the drawings to simplify the description.
FIG. 1 shows an embodiment of an oscillation circuit 1 according to the present invention, in which a plurality of signal inversion elements are connected in cascade in a ring shape, and a ring oscillation circuit section 2 is connected corresponding to each signal inversion element and its output. It comprises a constant current circuit section 5 for limiting current and a constant voltage circuit 4 for generating a constant voltage serving as a reference for defining a current value supplied to each signal inverting element.
[0011]
The configurations of the ring oscillation circuit section 2 and the constant current circuit section 5 will be described in more detail. The ring oscillation circuit unit 2 cascade-connects the input and output of n (n = positive odd number) signal inverting elements 2m (m = 1 to n) composed of a CMOS inverter circuit, a NAND circuit, and the like in a ring shape. In addition, a capacitor 3m for delaying transmission of a signal output is connected to the output of each signal inversion element 2m. Each signal inverting element 2m has its reference potential side transistor directly connected to the reference potential similarly to the conventional signal inverting circuit, and the power supply side transistor connected to the power supply voltage via each constant current source 5m of the constant current circuit 5. It has been configured. With such a configuration, the output current of each signal inverting element 2m and the delay time due to it are kept substantially constant without depending on the variation in the driving ability.
[0012]
The constant current circuit section 5 generates a constant current based on a constant voltage from the constant voltage circuit 4 using a resistor 5a and a diode-connected NMOS transistor 5b, and a transistor 5c that is current mirror-connected to the transistor 5b. And a transistor 5d serving as a load resistance thereof, a plurality of PMOS transistors 5m (m = 1 to n) which are current mirror-connected to the transistor 5d, and a transistor 5e for controlling the operation of the constant current circuit section 5. It is configured. The transistor 5m is inserted and connected in series with the power supply side transistor of each signal inversion element 2m.
[0013]
A control line S is connected to one input of the transistor 5e and one input of the NAND circuit 21, so that start and stop of oscillation can be controlled. The output of the inverter circuit 2n fed back to the NAND circuit 21 is an inverter. The output of the circuit 6 is also connected to another circuit (not shown) as the clock signal CP so that the operation timing of the semiconductor device can be determined.
[0014]
Each capacitor 3m may use only parasitic wiring capacitance or diffusion capacitance. However, if a capacitance element is separately formed to increase the capacitance value, it is possible to cope with a lower oscillation frequency and to oscillate. The accuracy of frequency creation can be further improved. The constant voltage circuit 4 may use a general constant voltage circuit using a forward voltage of a diode, a zener voltage of a zener diode, or the like, and thus a detailed description of the configuration is omitted.
[0015]
Next, the operation of the circuit will be described. When the voltage of the control line S is at the low level, the output of the NAND circuit 21 is fixed to the high level and the constant current supply to each signal inverting element is stopped, so that each signal inverting element keeps its previous output state. And the oscillation stops.
On the other hand, when the voltage of the control line S goes high, the output of the NAND circuit 21 is first inverted to a low level and the charge of the capacitor 31 is rapidly discharged, and the charge voltage of the capacitor 31 is reduced to the input threshold of the inverter circuit 22. When the voltage falls below the voltage, the output of the inverter circuit 22 is inverted, and the capacitor 32 is charged with the constant current from the transistor 52. When the charging proceeds and the charging voltage of the capacitor 32 exceeds the input threshold voltage of the inverter circuit 23, the output of the inverter circuit 23 is inverted and the charge of the capacitor 33 is discharged. When such a charging / discharging operation is repeated in each signal inverting element 2m, a signal of a different voltage level is fed back to the NAND circuit 22 because an odd number of signal inverting elements are connected in a ring. As a result, the oscillation operation continues.
[0016]
As described above, the charging of each capacitor 3m is performed by the constant current from the transistor 5m. Therefore, if the constant current value is set so that the charging time is sufficiently longer than the discharging time, fluctuations in the power supply voltage may occur. Irrespective of the fluctuation of the driving capability of the signal inverting element, a substantially constant delay time is obtained in each signal inverting element, and the oscillation frequency is kept substantially constant.
[0017]
The oscillation frequency can be changed by changing the number of signal inverting elements and the capacitance value of the capacitor as in the conventional case. However, in the case of the present embodiment, the resistor 5a for determining the constant current value is used. The output current of each signal inverting element and its delay time can be changed only by externally changing the resistance value so that the oscillation frequency can be easily changed.
[0018]
FIG. 2 shows another embodiment of a CMOS signal inversion element used in the present invention. FIG. 2A shows a transistor element on the power supply line side of a signal inversion element 2am (m = 1 to n) of an inverter circuit configuration. Indicates a state in which a constant current circuit 5am (m = 1 to n) is inserted and connected in series to the transistor element on the reference potential line side as in the conventional inverter circuit, as well as being directly connected to the power supply voltage. . If a plurality of the signal inverting elements are connected in cascade in a ring shape and a constant current value is set by a constant current circuit having a configuration similar to that of FIG. 1, an oscillation circuit can be configured. In FIG. 2B, constant current sources 5am and 5bm (m = 1 to n) are respectively inserted in series with each transistor element connected to the power supply line and the reference potential line in the signal inversion element 2bm (m = 1 to n). In this case, the connection is made, and the accuracy of the oscillation frequency can be further improved.
[0019]
FIG. 3 shows an IC card 100 in which an IC card is formed by using a semiconductor device 10 having a built-in oscillation circuit 1 of the present invention. The antenna 15 transmits and receives radio waves for power and data, and rectifies the received radio waves. A rectifier circuit 11 and a smoothing capacitor 16 for smoothing and obtaining a constant power; a power supply circuit 12 for supplying a power supply voltage to an internal circuit using the obtained power; and a data component of a received radio wave. , A modulation / demodulation circuit 14 for demodulating received data and modulating data to be transmitted, and the oscillation circuit 1 of the present invention described with reference to FIGS. 1 and 2. In addition, as a configuration not shown, there are a control circuit such as a microcomputer for processing received data and a storage device such as a FLASH memory for storing data. The power supply circuit 12 includes a power supply voltage detection circuit for stopping or initializing the operation of the IC card 100 when the power supply voltage becomes lower than a preset voltage value and malfunctions easily. It works only with voltage.
[0020]
Next, a usage example and an operation when the IC card 100 is used in a ticket gate system will be described. The power required by the IC card 100 is received by the antenna 15 at a frequency of about several hundred kHz and a weak radio wave of several μW transmitted from the transmitting antenna of the ticket gate when passing near the ticket gate (not shown). Then, the power is rectified by the rectifier circuit 11 and charged into the capacitor 16 to obtain a power supply voltage.
[0021]
While receiving this power supply, similarly, the radio wave such as the request number confirmation request data transmitted from the antenna of the ticket gate is received by the antenna 15, detected by the detection circuit 13, demodulated by the modem circuit 14, and demodulated. The control circuit such as a computer rewrites the data such as the fee and the number of times stored in the storage device, modulates the result by the modulation / demodulation circuit 14, and transmits the result from the antenna 15 to the ticket gate. In the same manner, the ticket gate device performs data reception processing to check the ID number and use status of the IC card 100, thereby guiding or passing only available people or objects or guiding them in a predetermined direction. Display is performed or data is changed again.
[0022]
Since the IC card is used in this way, if the power supply voltage obtained is low due to a low received signal level due to being away from a transmission device such as a ticket gate device, the oscillation frequency of a conventional IC card using an oscillation circuit is significantly increased. Although it took time to write data to the storage device at a later time, the IC card 100 using the oscillation circuit of the present invention can obtain a stable oscillation frequency even when the power supply voltage is low, so that it is substantially constant. The data processing can be performed in the time. Since the operation time is substantially constant, it is possible to prevent an increase in current consumption in the oscillation circuit, and to use the remaining power to perform transmission with higher power, thereby extending a communication distance. Also.
[0023]
It should be noted that the present invention is not limited to the configuration shown in the embodiment of FIG. 3, and it is needless to say that all the circuit functions of FIG. You may do it. Further, the storage device may be a non-volatile memory capable of holding stored data even when the power supply voltage is lost, and may be a built-in microcomputer or the like. The structure and material of the IC card 100 may be the same as those of the prior art, and the number and arrangement of the antennas may be arbitrary. Further, the oscillation circuit of the present invention can be used as a reference clock signal for a VTR or a TV device.
[0024]
As described above, according to the present invention, the IC card device according to the first aspect suppresses the fluctuation of the delay time of the signal inverting element of the oscillation circuit when the power supply voltage and the temperature fluctuate, thereby reducing the fluctuation of the oscillation frequency. Since the oscillator can be easily formed while suppressing the number of external components, there is an effect that an IC card device capable of transmitting and receiving data more reliably can be provided more easily . Furthermore, the oscillator used in the IC card device of the present invention can keep the delay time of the delay circuit including the signal inverting circuit and the capacitor substantially constant, and the oscillation frequency varies over a wide power supply voltage range and temperature range. There is an effect that it becomes possible to suppress. Further, since the oscillation frequency can be changed only by changing the constant current value that defines the output current of the signal inversion element, there is an effect that the initial oscillation frequency can be easily adjusted.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an embodiment of the present invention,
FIG. 2 is a circuit diagram showing another embodiment of a signal inversion element used in the present invention;
FIG. 3 is a circuit diagram showing a configuration example of an IC card using the semiconductor device of the present invention;
FIG. 4 is a circuit diagram showing an example of a conventional oscillation circuit.
[Explanation of symbols]
1: Oscillation circuit 2: Ring oscillation circuit section 2n: Signal inversion element (inverter element)
3: Capacitor element 4: Constant voltage circuit 5: Constant current circuit section CP: Clock signal S: Control signal

Claims (1)

An IC card device using a semiconductor device incorporating a ring oscillation circuit in which an odd number of signal inversion elements are connected in cascade in a ring shape as an oscillation circuit of a non-contact type IC card which rectifies a received signal and uses it as a power supply. ,
At least one of in series with the constant current circuit is set to less current value than the current capacity of the power supply side transistors of the power supply side transistor connected to the power supply voltage or reference potential of the transistors constituting the plurality of signal inversion element An IC card device, wherein the transistors constituting the above are connected to each other.

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