RTC Module Benchmark

In this article, we will compare the RTC module that we often use in projects that need clock processing with other alternative modules. First of all, we would like to point out that the RTC modules in this table are the most widely available and frequently used modules on the market, there are different and non-RTC modules in this table.

When it comes to measuring time in microcontrollers, there are many ways to do things. For the fastest purposes, such as rection delays or other standby situations, counting only a few cycles of the main clock will serve the purpose. Up to tens of milliseconds of truth, they can do this without consuming a lot of energy.

The RTC you select for a specific project will depend on several factors. While battery-powered projects benefit from low power consumption, scientific measuring instruments may need the highest accuracy over time. Communication protocols are also important, as the implementation of an RTC in an existing design may require part selection due to the presence of I2C or SPI.

Since parts are inexpensive, the budget for those working in this area is usually not a problem, but a production of thousands of pieces will save a lot in quantity from a cheaper part. As always, having a clear idea of project requirements is the key to choosing the right component for the job.

Comparison of Modules

For Those Who Say Only Time Is Enough: DS1307

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For microprocessors and watch experimenters, the DS1307 is an ideal and inexpensive RTC module. Thanks to the spare battery slot on the back surface of the circuit board, it can continue to operate without delay through its own battery, even if the development card or the source to which it is connected stops working. Powered by 5V, this module attracts 500nA current and uses an external 32,768 kHz crystal. Due to the design and noise of the circuit board, it sometimes makes deviations in the time count, so it should not be preferred in cases where timing is important. However, to save data, it is ideal for a simple project. Here you can see the details by looking at the datasheet.

Communication protocol: I2C, Default I2C Address: 0x68

High Accuracy and Alarm Requesters: DS3231 (I2C), DS3234 (SPI)

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For those who need accuracy they can rely on, an RTC module with an integrated oscillator is very important. These devices guarantee factory accuracy, since there is no possible user design error in the installation of the crystal. Modules such as DS3231 and DS3234 are suitable for this recipe with temperature-compensate crystal oscillators (TCXO) with a sensitivity as good as ±2 ppm at temperatures between 0°C and +40°C. However, it has an unfamiliar power consumption in other modules, such as 1500 nA.

These modules are more modern, can operate at voltages between 2.3-5.5V and are easy to use with a variety of different microcontrollers. They also have square wave and alarm outputs. These can be used to create clocks for other hardware or to wake microcontrollers through a GPIO pin set as a interrupt. RTCs are widely used in this way to keep the main microcontroller in low-power sleep mode and make the most of battery-powered projects by waking up only when needed. There is also a built-in extra temperature sensor that can be readable, which can be useful in some projects.

Communication protocol: I2C and SPI , Default I2C Address: 0x68

Low Power Consumption and All Remaining Features: RV-1805, RV-3028

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When it comes to battery power, each plan and project is important. For projects implemented in the field, it is often even more important to replace batteries regularly or guarantee a continuous supply of energy from alternative sources such as solar or wind, as it is often impractical.

For applications like this, the RV-1805 and its newer backup, the RV-3028, are activated. Party parts, complete with alarms and other high-end features, certainly attract a very small current. With a special mode based on a crystalline low-power RC oscillator as a calibration backup, the RV-1805 pulls only 22 nA in time-operation mode.

This uses a supercapacitor that can only maintain the time set for a full 35 days of Sparkfun's module, when other RTCs should rely instead on batteries. The RV-3028 raises this to 100 nA and demands a potential uptime of 9 years with the supplied battery. Accuracy in these parts is also highest (±2 ppm RV-1805, ±1 ppm RV-3028), making them perfect for accurate data recording in remote environments.

Extra: RTC Module for Single Card Computers

Like many computers from the 1980s, the Raspberry Pi lacks a real-time watch. This eliminates the need for a battery, but can also cause damage to system logs and other tasks, especially in non-networked environments. Fortunately, most of the RTC devices listed above are available in special modules designed for the special form factor of the Raspberry Pi. All kinds of modules up to the DS1307, DS3231 are available for the Raspberry Pi.

Installing these modules takes some effort. The vast majority communicate via I2C, which can be a headache for projects that already use the interface for other purposes. In addition, you need to install a utility to communicate with RTC and use it to properly update the system clock as needed.

You can also use it with other single card computers whose pin scheme is similar to the Raspberry Pi.

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DS1307 Line
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