Time-measurement device for applications without power source

Abstract

The present invention relates to a time-measurement device comprising a timing-reference circuit on a single substrate or on multiple substrates; a source of radioactive radiation on or in the substrate; and a counter for radioactive decay events on or in the substrate. A control circuit on the substrate is configured to control the integration time of the counter using the timing reference, receive the count signal from the counter, and calculate a time difference between a momentaneous time and a reference time using the count signal, the value of the integration time span, the half life, and a known decay rate of the at least one radioisotope at the reference time.

Description

technical field [0001] The invention relates to a time measuring device, a real time clock, and to an electrical assembly comprising a real time clock circuit. The invention also relates to a card-like identification or authentication device and to a method for measuring time relative to a reference time. Background technique [0002] The use of radioactive decay to measure time in integrated circuits is known in the art, eg US4,676,661. The time measuring device disclosed in US 4,676,661 is intended to replace quartz oscillator based time measurement by periodically providing an electrical signal to count time in seconds by counting radioactive decays up to a preset number of decay counts. Although US4,676,661 is in Figure 5 Calculation of time elapsed since manufacture is also contemplated in embodiments, but this time calculation is only performed with year precision. [0003] Time measurement has received attention for incorporation into many other application devices...

AI Technical Summary

Problems solved by technology

However, many of these applications, such as RFID tags and identification cards, bank cards, etc., are usually not continuously connected to a power source

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