What is a programmable calibration adjustment?

Real Time ClockFunction

• Nisshinbo Micro Device RTCs have a programmable calibration adjustment from -189 ppm to +189 ppm or -63 ppm to +63 ppm. The crystal oscillator used in Nisshinbo Micro Device RTCs provides 32,644 to 32,892 pulses per 20 seconds or 60 seconds while a normal crystal oscillator provides exactly 32,768 pulses per second.

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  • *)Nisshinbo Micro Device RTCs perform this calibration adjustment every 20 or 60 seconds. (Notes: R2025/R2045 performs a calibration adjustment evey 20 seconds.)

Tuning fork crystal provides highly stable natural oscillation frequency; however, environmental changes of temperature, humidity, pressure, vibration or a capacitance formed on a substrate can change the resonant frequency of a crystal oscillator.

When performing a capacitor matching evaluation using a PCB for mass production, those influences need to be considered. Nisshinbo Micro Device RTCs have a programmable time register to adjust a timekeeping glitch without the need of additional capacitors, which makes the capacitor matching evaluation easier.

• A tuning fork crystal is usually cut such that its frequency over temperature is a parabolic curve centered around 25°C. Nisshinbo Micro Device's programmable calibration circuit have an external temperature sensor to compensate this deviation.

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  Uncompensated Crystal Drift

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  Nisshinbo Micro Device RTCs Compensated Crystal Drift