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Ricoh RTCs have a programmable calibration adjustment from −189 ppm to +189 ppm or −63 ppm to +63 ppm.
The crystal oscillator used in Ricoh 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.
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. Ricoh 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. Ricoh's programmable calibration circuit have an external temperature sensor to compensate this deviation.
Uncompensated Crystal Drift
Ricoh RTCs Compensated Crystal Drift