Static information storage and retrieval – Powering – Data preservation
Patent
1992-05-12
1993-11-30
LaRoche, Eugene R.
Static information storage and retrieval
Powering
Data preservation
365229, G11C 514
Patent
active
052672115
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a memory card mounted with a storage device and an electronic appliance using such memory card, and particularly relates to reduction of soft errors.
2. Background Art
In a conventional memory card, an externally supplied source voltage was applied to a storage device, for example, a RAM, built in the memory card in use of the memory card, while in not-use, the storage device was backed up by a battery built in the memory card so as to maintain the data stored therein. In such a backup state, however, the rate of occurrence of soft errors was high in comparison with that in use of the memory card so that an electronic appliance mounted with the memory card operated erroneously or the stored data became changed.
By the way, soft errors are temporary errors having no reproducibility, and soft errors caused by .alpha. rays have come into serious problems affecting the reliability of memory elements. Soft errors due to .alpha. rays are caused when .alpha. particles, which are produced when a very fine quantity of radioactive isotope uranium (U) or thorium (Th) included in a package or the like .alpha.-decays, come into the surface of a memory chip. The incident .alpha. particles produce a number of electron and positive-hole pairs in the vicinity of the chip surface, so that the electrons concentrate in a memory cell to thereby break the information of the memory cell.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a memory card in which the rate of occurrence of above-mentioned soft errors at the time of backup is reduced.
It is another object of the present invention to provide an electronic appliance mounted with a memory card in which the rate of occurrence of soft errors is reduced.
The present invention is based on the knowledge that the larger the voltage applied to memory elements, the more reduced the rate of occurrence of soft errors, and the present invention has been attained in the circumstances that the upper limit of the voltage value of batteries applicable to devices such as memory cards which are restricted in fixing conditions is 3V at present and there exists no buttery having an output voltage higher than 3V.
According to an aspect of the present invention, the memory card comprises an RAM, a battery, a voltage converter for boosting a voltage of the battery and for outputting the boosted voltage, and a switching circuit for receiving an output voltage of the voltage converter and an externally supplied voltage and for supplying one of the output voltage of the voltage converter and the externally supplied voltage to the RAM as a driving voltage therefor. For example, in the state where the memory card has been removed from an electronic appliance, the external voltage is not supplied so that the switching unit supplies the output voltage of the voltage converter, that is, the output voltage obtained by boosting the voltage of the battery, to the RAM as a backup voltage therefor. As has been described, at the time of backup, a voltage higher than the voltage of the battery is supplied to the RAM as a backup voltage therefor, so that soft errors can be reduced on a large scale.
Further, according to another aspect of the present invention, the memory card comprises a voltage monitor for supervising the externally supplied voltage so as to bring the voltage converter into an operation inhibition mode when the externally supplied voltage is equal to or higher than a predetermined value. Since the voltage converter does not have to operate at any time other than the time of backup, the operation of the voltage converter is inhibited when the memory card is driven by an electronic appliance to thereby realize low power consumption.
Further, according to another aspect of the present invention, the voltage converter includes a clock generator circuit for generating a clock signal, and a voltage converter circuit for receiving the clock signal and for boosting the voltage of the battery.
Further, acco
REFERENCES:
patent: 4654829 (1987-03-01), Jiang et al.
patent: 4712195 (1987-12-01), Finger
patent: 4912346 (1990-03-01), Mizuta
patent: 5046052 (1991-09-01), Miyaji et al.
patent: 5058075 (1991-10-01), Mizuta
patent: 5153855 (1992-10-01), Konishi
patent: 5168206 (1992-12-01), Jones
Kobayashi Ichiro
Sakurada Noriaki
Yamada Atsushi
Kessell Michael C.
LaRoche Eugene R.
Seiko Epson Corporation
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