IC card with dual level power supply interface and method for operating the IC card
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United States of America Patent
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Feb 6, 1996
Grant Date -
N/A
app pub date -
Mar 23, 1994
filing date -
Mar 23, 1993
priority date (Note) -
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Abstract
An objective of the present invention is to provide a highly reliable IC card which is large in the scale of integration, fast, and low power-consuming, which contains the latest type of IC that has an operating voltage of 3.3 V and a maximum rated voltage of 5 V or less, and which can be used in either the latest equipment rated at 3.3 V or existing equipment rated at 5 V, or which does not cause this latest type of IC to be destroyed. The interface circuit comprises an analog switch, an external interface circuit, an interval interface circuit, and a high-voltage detection circuit. If the voltage of the power supply Vcc of the host system is less than or equal to an upper-limit voltage of 4 V, the power supply voltage is applied unchanged through the analog switch to a ROM that is the main circuit. On the other hand, if the power supply voltage is greater than this upper-limit voltage of 4 V, the analog switch is made non-conductive and thus the power supply voltage is not applied to the ROM. This prevents the ROM from being destroyed. If a regulated-voltage circuit is also provided, a power supply voltage regulated at 3.3 V can be applied to the ROM, even when the power supply voltage of host system is greater than the upper-limit voltage of 4 V.
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