Registers – Records – Conductive
Reexamination Certificate
1998-03-03
2001-05-01
Lee, Michael G. (Department: 2876)
Registers
Records
Conductive
C235S487000, C235S451000
Reexamination Certificate
active
06223990
ABSTRACT:
TECHNICAL FIELD
This invention relates to a semiconductor device incorporating into an oscillating circuit, an IC card utilizing the same and a communication system.
BACKGROUND ART
In recent years, a proximity type IC card, hereinafter abbreviatedly called as “the IC card” has being brought into usage, which is capable of confirming and updating data contained therein without manually passing through a card reader at a card gate or the like, whenever it is used. Such card, called as “a radio-frequency tag” is used as a card tag in an application such as coupon tickets for skiing-ground rifts, coupon or commuter tickets for trains or buses, inventory management, and so on.
The IC card of this kind has a structure as shown in
FIG. 4
, wherein in (a) of
FIG. 4
is a perspective view viewed from the above and in (b) of
FIG. 4
a perspective view viewed from the side. As shown in the figure, a fixing resin
34
has a thickness of approximately 0.5 to 2.0 mm to incorporate to fix therein a substrate
31
which has semiconductor devices and discrete electronic parts previously mounted thereon and an antenna
32
formed spiral in the form of a coil. The fixing resin
34
has a surface patched with a film
33
, which is formed of polyethylene-terephthalate, or PET, or the like to a thickness of approximately 0.1 mm to have a given mark assigned previously. The substrate
31
has a wiring pattern formed beforehand by printing to allow mounting thereon a semiconductor device such as a micro-computer and memories as well as discrete electronic components involving resistors, capacitors, etc. The antenna
32
, serving for transmission and reception of an electromagnetic waves, constitutes a tuning circuit in association with a capacitor forming a resonant circuit.
FIG. 5
shows a general example of a communication system utilizing an IC card. The communication system of
FIG. 5
comprises an IC card
10
a
having an independent data and a card-gate apparatus
20
a,
which apparatus serves to transmit an electromagnetic wave to supply electric power to the IC card
10
a,
as well as perform transmission and reception of data. The IC card
10
a
comprises an antenna
22
a
for receiving an electromagnetic wave, a rectifying circuit
11
with a capacitor
6
to rectify the received electromagnetic wave for creation of electric power, a power source circuit
12
for supplying an internal circuit of the IC card
10
a
with power source voltage created from the obtained electric power, a wave-detecting circuit
13
for detecting a data component from the received electromagnetic wave, a modulating/demodulating circuit
14
for demodulating the received data and modulating data to be transmitted, an oscillating circuit
1
for generating a clock signal CP to be supplied into internal circuits, a control circuit formed by a micro-computer and memories, not shown, respectively for processing and storing the obtained data.
On the other hand, the card-gate apparatus
20
a
comprises a modulating circuit
14
a
for modulating an electric power signal and a data signal to be transmitted to the IC card
10
a,
an antenna
22
f
for transmitting electromagnetic waves for carrying them, an antenna
22
g
for receiving an electromagnetic wave from the IC card
10
a,
a detecting circuit
13
b
for detecting a data component of the received electromagnetic wave from the IC card
10
a,
a demodulating circuit
14
d
for demodulating the detected data, and a control circuit
15
a
for processing the demodulated data to permit the card-gate apparatus, not shown, to perform control depending on the result of data processing. The control circuit
15
a
comprises a semiconductor device such as a micro-computer and memories, whereas the card-gate apparatus is constituted by a gate device for controlling passage, a guiding display, and so on.
Conventionally, there have been oscillator circuits, which are incorporated into the IC card
10
a,
such as CR oscillator circuits and ring oscillator circuits, which are easy to configure for integration for a semiconductor device without using components such as ceramic-quartz oscillators and inductance elements. These circuits were often used by incorporation within a semiconductor device. There is shown as an example in
FIG. 6
a ring oscillating circuit
9
of a CMOS structure having odd numbers of signal inverters
9
m,
wherein m=1−n: n is a positive odd number, of such as NAND circuits and inverter circuits. These signal inverters have their input and output terminals for connection of tandem in the form of a ring. The signal inverters
9
m
have delaying capacitors
3
m,
respectively, connected to output terminals thereof. The inverter
9
n
is connected for supply a signal to one input terminal of a NAND
9
1
as well as to an input terminal of an inverter
6
whose output terminal is connected to supply a clock signal CP to other circuitry, not shown, where it can be used as a reference clock for a semiconductor device. The other input terminal of the NAND
9
1
is connected to be supplied with a control signal S for enabling control of commencement and halt of oscillation.
In the meanwhile, ring oscillating circuits, CR oscillating circuits, etc. as stated above were used without problem in devices such as toys, where close precision is not necessary for oscillation frequency. However, they were difficult to use as a device for a card-gate system utilizing an IC card of the proximity type, due to reasons as discussed below.
That is, there is a demand for relatively close precision in oscillation characteristics in a card-gate system utilizing a proximity type IC card, due to the necessity of matching in timing of data transmission and reception between an IC card and a card-gate apparatus. However, an IC card has solely a power source where an electromagnetic wave transmitted from a card-gate apparatus, etc. is received and rectified therein to charge electricity on a capacitor, so that the voltage of the power source is apt to vary depending on the distance from the card-gate apparatus or a state of data reception. The variation of power source voltage causes variation in drivability of each signal inverter, so that each capacitor is changed of its charging or discharging current to vary delay time among the signal inverters, thereby resulting in variation in oscillation frequency. The drivability of each signal inverter also is readily varied by change of temperature or variation of device characteristics incurred through fabrication of a semiconductor device. Thus, oscillation frequency is further varied.
In this manner, the oscillation frequency is varied by various factors. As a consequence, the median oscillation frequency was conventionally controlled by altering the size or the number of transistors involved in a signal inverter, or otherwise vary the size of capacitors to alter the capacitance value. These alterations, however, is impractically troublesome because it necessitates a change of masking or the like used during fabrication of a semiconductor device.
As for oscillating circuits built-in semiconductor devices, there were also no techniques to suppress the variation of oscillation frequency, but for limiting such condition as power source voltage and temperature to meet the frequency-precision requirement.
Incidentally, the usage of external component parts such as discrete oscillators is expected to readily improve the frequency precision. However, it is still difficult to adopt, because an IC card as a product has a limitation in its thickness, the external-part mounting makes the substrate area large, the increased number of pins becomes necessary for packaging, the cost is raised by additional expensive cost, including control cost, for external parts.
It is therefore the object of the invention to form within a semiconductor device an oscillation circuit for presenting an oscillation frequency, which is relatively precise over a wide range of power source voltage and temperature and easy to alter, thereby facilitating the
Baker & Botts LLP
Franklin Jamara A.
Lee Michael G.
Rohm & Co., Ltd.
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