What is a Real Time Clock? RTC Module Mechanisms and Uses

Overview of Real Time Clocks (RTC)

What is a real time clock (RTC)?

An RTC (Real Time Clock) is a dedicated IC that generates and outputs time, date, and other digital data from a clock source. It may also refer to functional blocks and software that realize these same functions.

How do real time clocks (RTC) work?

A basic RTC consists of a crystal unit as a clock source, its oscillator circuit, and a date/time counter circuit. Applying a voltage to the crystal produces a phenomenon called the "piezoelectric effect,” generating a small electric charge. This electric charge is amplified and fed back to the crystal to obtain a constant frequency signal. The oscillation signal of the crystal unit is used as the clock source of the date-time counter circuit to generate date-time data. Quartz crystals have the most stable oscillation frequencies among all piezoelectric materials and therefore generate highly accurate time data.

What are Real Time Clock Modules (RTC Modules)?

What is an RTC module?

RTC functions can be embedded in an MCU, but you can also use either a separate RTC module or a discrete RTC (called an RTC IC or RTC chip). Separating the RTC from the MCU allows the time to be kept independently, even when the MCU is in Sleep mode. As explained below, RTC modules have crucial advantages over discrete RTCs.
An RTC module is a single package that contains an integrated RTC IC, oscillator circuit, and master clock.

Differences between an RTC module and an RTC IC

Unlike RTC ICs, RTC modules contain the necessary components in a single-package, so users don’t have to design their own oscillator circuits or make frequency adjustments.
RTC modules can save board space, since they reduce the number of discrete components. They also have the advantage of being less susceptible to influence from the external environment.

Three configurations that provide RTC functions and the features of each

Main uses of RTC modules

Even when the MCU is in sleep mode, an RTC module can continue timekeeping and wake the MCU up at a specified interval or any designated time using its wake-up timer or alarm. This allows the MCU’s active time to be minimized, leading to significant reductions in overall system power consumption.
- Examples of use : MFP (Multifunction Peripheral), Automotive BMS (Battery Management System), etc.

Due to superior timekeeping precision, these models are widely adopted in applications where minimizing time drift is critical or where periodic time synchronization with a server is not possible.
- Examples of use : Infortainment, Smart Lighting, etc.

High Accuracy and Low Current Consumption! Epson's RTC Module Uses a Quartz Crystal Unit

Overview of Epson's RTC modules

Epson's RTC modules are a single-package solution that combines an RTC IC, which is equipped with an oscillator circuit and date-time counter, with a crystal unit that has been optimally designed for it.
Epson fabricates its own quartz crystals and ICs, ensuring that its RTC modules provide high accuracy and low current consumption. These modules can reduce power consumption and increase efficiency in systems with a variety of features and functions.

Features of Epson's RTC modules

- The single-chip integrated design saves and eliminates the need for a power supply switching circuit.
- Temperature compensation limits frequency drift to within ±9 seconds per month. *Limited XA accuracy product (-40℃ to +105℃ environment)
- Reduce power consumption in Sleep mode.
- No circuit matching required, saving time and work.
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