A "Stitch" in Time: Accurate Timekeeping with On-Chip Compensation

Applications like Energy Meters that rely on real time data require accurate time under all environmental conditions. Typically, these applications rely on Real Time Clock (RTC) for all real time operations but there are many factors like crystal aging, incorrect loading and temperature variations that tend to change the frequency of the clock used for RTC resulting in inaccurate time. Hence there is an unavoidable need to have compensation technique inside the RTC to counter balance this error in clock frequency of crystal. This paper describes a digital hardware compensation technique which compensates by adding or removing pulses in a particular timing window thus maintaining accurate clock. Technique described in this paper uses simple hardware to ensure low power consumption thus maintaining longer battery life. This enables applications to use cheaper crystal that may be inaccurate and compensate for the inaccuracies within the hardware thus reducing board cost.