US 5,490,117 AGranted

IC card with dual level power supply interface and method for operating the IC card

AssigneeSeiko Epson Corporation

InventorsZenzo Oda, Noriaki Sakurada

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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.

Claims36

Dependent claims

An IC card comprising a main circuit, a connector for connecting said IC card to a host system, and an interface circuit provided between said connector and said main circuit, wherein:

said interface circuit comprises:
an external interface circuit for connecting said host system to an internal interface circuit, a power supply line of the external interface circuit being connected to a first power supply line that is a power supply line from said host system;
said internal interface circuit for connecting said external interface circuit to said main circuit, a power supply line of the internal interface circuit being connected to a second power supply line that is a power supply line of said main circuit;
voltage detecting means for detecting a voltage of said first power supply line;
switching means for selectively connecting and disconnecting said first power supply line and said second power supply line based on a detection result of said voltage detection means, said switching means connecting said first power supply line to said second power supply line when an absolute value of said voltage of said first power supply line is less than an absolute value of a prescribed voltage, said switching means disconnecting said first power supply line from said second power supply line when said absolute value of said voltage of said first power supply line is at least said absolute value of said prescribed voltage.

2 more elements

An IC card comprising a main circuit, a connector for connecting said IC card to a host system, and an interface circuit provided between said connector and said main circuit, wherein said interface circuit comprises:

an external interface circuit for connecting said host system to said main circuit;
voltage detection means for detecting a voltage of a first power supply line that is a power supply line from said host system;
switching means for selectively connecting and disconnecting said first power supply line and a second power supply line based on a detection result of said voltage detection means, said second power supply line being a power supply line of said main circuit, said switching means connecting said first power supply line and said second power supply line when an absolute value of said voltage of said first power supply line is less than an absolute value of a prescribed voltage, said switching means disconnecting said first power supply line from said second power supply line when said absolute value of said voltage of said first power supply line is at least said absolute value of said prescribed voltage.

Dependencies are inferred from the claim text.

Facts

Application: 08/216,272Filed 23 Mar 1994
Priority: JP 5-06434723 Mar 1993
Granted: 6 Feb 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01R 31/31715
Input or output aspects: testing of input or output circuits; test of circuitry between the I/C pins and the functional core, e.g. testing of…
G11C 5/143
Power supply arrangements , e.g. power down, chip selection or deselection, layout of wirings or power grids, or multiple supply levels: detection…
G11C 5/147
Power supply arrangements , e.g. power down, chip selection or deselection, layout of wirings or power grids, or multiple supply levels: voltage…
G01R
Measuring electric variables