US Patent 8963647 Self-powered timer apparatus

A method is provided for implementing a timer using a floating-gate transistor. The method includes: injecting a charge into a floating-gate transistor at an initial time, where a gate terminal of the floating-gate transistor is comprised of polysilicon encased by an insulating material; creating lattice imperfections at boundary of the polysilicon to cause leakage from the floating-gate transistor; measuring current read out from the floating-gate transistor at a time subsequent to the initial time; and determining an amount of time between the initial time and the subsequent time using the measured current.