What Are Real Time Clocks (RTC) and How Do They Work?
Exploring These Popular Electrical Components

A real time clock, or RTC, is a digital clock designed with a main function of keeping ongoing accurate time, including when the power supply to a device is cut off or reduced to low function. RTCs are a combination of a controller, oscillator, and an embedded quartz crystal oscillator that outperforms discrete electronic components, simplifies integration in new designs, and accelerates time to market.

Registers are the functions of real time clocks. Register data is programmed into the memory of the RTC and updated periodically, even during regular operation. RTCs are designed with a power switch function that can shift to being supported by a battery or other backup power source. This allows the RTC to continue providing precise and consistent time counts, even when the power is cut off or the unit enters sleep mode.

These sophisticated components are the backbone of many devices we use on a daily basis including alarms, timers, and more.

How Are Real Time Clocks Used Today?
Real time clocks are utilized across many industries and applications in different ways. These industries and applications include:

Internet of Things (IoT), like GPS systems and smart home technology
Wearable technologies, like smartwatches and fitness trackers
Consumer products
Automotive electronics
Medical product applications
And more

Many modern products rely on batteries for their power supply, so they have minimal access to replacement batteries and recharging options. This lack of power options places restrictions on how much certain functions and sensors can operate. Continuous operation of all systems and functions drains battery power quickly. That’s where RTCs come in. Engineers have found that having a scheduled intermittent activation of the device helps extend the battery life. Real time clocks allow the engineer to design power saving protocols into the device by powering down high usage functions when not in use. RTCs are interesting in that they can operate at low energy when required, but still maintain accurate timekeeping and alarm functions when needed.

RTCs solve many problems for engineers because they stay on and operate at the lowest possible usage level when no task is required. The sophistication of these devices is critical to the design of many electronics, medical equipment, industrial products, and other products that benefit from power saving and backup timekeeping.

Interruptions and Variations
Real Time Clocks can provide various interrupt functions to a system. In fact, the RTC can be programmed to signal an alarm or trigger that provides a full clock and calendar for use. What’s even more useful is that the interrupt functions actually still operate when a backup power supply is being used, completed with a digital timestamp of each event to ensure consistency and proper function. Some examples of potential interrupts include:

Periodic time updates
Periodic countdown for timers
Low voltage detectors
Automatic power source switchover
Power on reset
Alarms

Alarm triggers are reliant on the timing settings in the registers. When the time matches the setting’s registers, the alarm interrupt is triggered. This same logic is applied to countdown timers and timed event notifications.

Potential Power Supply and Backup Power Sources
Most RTCs will begin by relying on the main system power supply for function, with an identified backup power source already established. The most common backup power sources include coin cells, rechargeable batteries, MLCCs, or super capacitors. Some RTCs will also be close enough to another source to rely on as well.

Real time clocks can’t afford interruptions, so understanding where power is coming from in all situations is imperative for accurate and consistent timekeeping without interruption.

Does Your System Require a Real Time Clock?
Now that the value of these real time clocks has been established, many engineers and designers have probably already envisioned some uses for RTCs in their systems. If your project can benefit from consistent timing and reliability, you’ll be surprised at the online presence of manufacturers carrying these and other electronic components.

The most efficient way to approach finding a source for a real time clock is to find a specialist to partner with. They can ask questions about your application to gain a better understanding of the electronic components you need to meet your requirements. Components are extremely particular so it is important to find the correct size, specs, and function before adding any component to your design. Working with an expert helps put you on the path to the highest possible efficiency and performance from your system.