Clock functions often have a backup power circuit, so they can continue to keep time while the primary source of power is off or unavailable. Although keeping time can be done without an RTC, using RTC has benefits of reducing the size and the cost of developing a backup circuit board since it only requires extremely low consumption current and very low input voltage.
Back-up Time Measurement (R2051S01)
|Backup Device||Backup Time|
|Backup Starting Voltage: 5V||Backup Starting Voltage: 3V|
|Coin Cell Primary Battery (CR2032)||-||10 Years or more (Calculated Value)|
|Electric Double Layered Capacitor (1 F)||130 Days||116 Days|
|Electric Double Layered Capacitor (0.1 F)||21 Days||15 Days|
|Aluminum Electrolytic Capacitor (4700 µF)||20 Hrs||12 Hrs 30 Min|
|Aluminum Electrolytic Capacitor (470 µF)||2 Hrs||1 Hrs 15 Min|
|Aluminum Electrolytic Capacitor (47 µF)||12 Min||7 Min 30 Sec|
RTCs are specifically designed for keeping track of the current time and calendar. The clock function of RTCs tracks hours, minutes and seconds. The calendar function of RTCs tracks year, month, date, day-of-the-week and is accurate through 2099, with automatic leap year/ long month/ short month correction. By integrating RTCs, the need of developing a complicated software for tracking time and calendar can be omitted.
RTCs have peripheral components for the oscillator circuit built in, so an oscillator circuit can be easily configured by only adding a crystal resonator as an external component.
Using RTCs can facilitate a layout design of oscillator circuit which is susceptible to noises.