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
These RTCs provide a power-on reset function, an oscillation halt sensing function and a supply voltage monitoring function.
These functions can be applied to judge a clock data validity.
These RTCs have a backup battery switch-over circuit which detects power failures and automatically switches to the battery supply when a power failure occurs. They are also equipped with two or three power supply pins so there is no need of adding a diode.