ISL12022 RTC accuracy optimization calibration procedure

Real Time Clock (RTC) devices contain an oscillator and normally require a crystal to operate with the required accuracy. Most commonly used 32.768kHz crystal oscillators have a frequency tolerance of ±20ppm at +25°C, and a nonlinear parabolic temperature drift 锟紸lpha锟? of -0.034ppm/°C?. Alpha is parabolic in nature, worsening as the crystal temperature deviates from the turnover temperature, referred to as T0 of the crystal, commonly +25锟紺.

This application note describes a simple trimming procedure, which optimizes the accuracy of an ISL12022 RTC and presents data for a variety of crystals with calibrated vs. uncalibrated.

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