Real-Time Clock (RTC) Component for Data Loggers

Product Specifications

Technical details and manufacturing context for Real-Time Clock (RTC)

Definition

A Real-Time Clock (RTC) is a specialized integrated circuit or module used in data loggers and other electronic systems to maintain accurate timekeeping even when the main system is powered off. It operates using a quartz crystal oscillator to generate precise timekeeping signals, counting seconds, minutes, hours, days, months, and years. When the main system is powered down, a small backup battery, typically a lithium coin cell, maintains power to the RTC circuit, allowing it to continue keeping time. Communication with the data logger's main processor occurs via serial interfaces like I²C or SPI to read/write time data. This ensures precise timestamping for logged data entries, enabling chronological accuracy and synchronization across multiple data collection points. The RTC is designed for industrial applications, with a typical timekeeping accuracy of ±2 ppm at 25°C for TCXO-based variants. It operates over a supply voltage range of 1.8–5.5 V, with a backup voltage range of 1.3–5.5 V for battery operation. Active supply current is typically 0.5–2 mA at 3.3 V during I²C communication, while standby current for timekeeping only is 0.3–1 µA. The operating temperature range is -40 to 85°C, with storage from -55 to 125°C, and non-condensing humidity tolerance of 5–95% RH. The RTC supports standard I²C interface up to 400 kHz, provides time in HH:MM:SS format (24-hour or 12-hour with AM/PM), and calendar in YYYY-MM-DD with leap year compensation up to 2100. It is commonly available in SOIC-8 surface-mount packages, weighing approximately 0.1–0.3 g. These specifications are typical reference values; actual values must be confirmed with the manufacturer for the specific model and application.

Working Principle

The RTC uses a quartz crystal oscillator to generate a stable frequency, typically 32.768 kHz, which is divided to count seconds, minutes, hours, and calendar dates. When the main system is powered off, a backup battery (lithium coin cell) supplies power to the RTC circuit, allowing it to continue timekeeping. The RTC communicates with the main processor via I²C or SPI interfaces, enabling the processor to read the current time and set alarms or timestamps. The oscillator's accuracy is affected by temperature, but TCXO-based RTCs maintain ±2 ppm accuracy at 25°C. The RTC also handles leap year compensation up to 2100. The backup voltage range is 1.3–5.5 V, ensuring operation during power loss. The RTC's low standby current (0.3–1 µA) extends battery life. The interface operates up to 400 kHz, and the RTC supports both 12-hour and 24-hour time formats. The RTC is designed to operate in industrial temperature ranges (-40 to 85°C) and can be stored in -55 to 125°C. The RTC's timekeeping function is independent of the main system, providing reliable timestamps for data logging.

Common Materials

Silicon (IC), Quartz crystal, Lithium battery

Technical Parameters

Parameter	Typical range	Notes & selection driver
Timekeeping Accuracy	±2 ppm	At 25°C, typical for TCXO-based RTCs
Supply Voltage	1.8–5.5 V	Wide range for battery or main power
Backup Voltage	1.3–5.5 V	For battery backup operation
Supply Current (Active)	0.5–2 mA	At 3.3V, I2C communication
Supply Current (Standby)	0.3–1 µA	At 3.3V, timekeeping only
Operating Temperature	-40–85 °C	Industrial grade
Storage Temperature	-55–125 °C	Non-operating
Humidity (Non-condensing)	5–95 % RH	Relative humidity range
Interface	I2C	Standard interface, up to 400 kHz
Time Format	HH:MM:SS	24-hour or 12-hour with AM/PM
Calendar Format	YYYY-MM-DD	Leap year compensation up to 2100
Package Type	SOIC-8	Common surface-mount package
Weight	0.1–0.3 g	Typical for SOIC-8

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Quartz Crystal Oscillator
Generates precise timing pulses for timekeeping

Material: Quartz crystal, metal electrodes
CMOS Integrated Circuit Part
Processes timing signals and manages time/date registers

Material: Silicon semiconductor
Backup Battery Holder Part
Secures and connects backup power source to maintain timekeeping during main power loss

Material: Plastic, metal contacts
Communication Interface Pins Part
Provides electrical connection for data exchange with main processor

Material: Copper alloy, gold plating

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Data Logger

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Central Processing Unit (CPU)

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Manufacturers of Real-Time Clock (RTC)

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Frequently Asked Questions

What is the typical accuracy of an RTC?

Typical timekeeping accuracy is ±2 ppm at 25°C for TCXO-based RTCs. This means a drift of about 2 seconds per million seconds, or roughly 1 minute per year. Actual accuracy depends on temperature and the specific model.

How does the RTC maintain time when the main power is off?

The RTC uses a backup battery, typically a lithium coin cell, to power the timekeeping circuit when the main system is off. The backup voltage range is 1.3–5.5 V, and the standby current is very low (0.3–1 µA), allowing the battery to last for years.

What communication interfaces does the RTC support?

The RTC supports standard I²C interface up to 400 kHz. Some models may also support SPI, but the listed specification is I²C. The interface is used to read and write time and date data.

What are the operating temperature limits?

The operating temperature range is -40 to 85°C, and storage temperature is -55 to 125°C. Humidity tolerance is 5–95% RH non-condensing. These are typical industrial-grade specifications.

Data Basis

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Preliminary Technical Classification

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voltage:	1.8V to 5.5V (typical operating range)
accuracy:	±5 ppm to ±20 ppm (typical timekeeping accuracy)
temperature:	-40°C to +85°C (industrial grade), -40°C to +105°C (extended industrial)
backup current:	100nA to 500nA (typical battery backup current)

Real-Time Clock (RTC)

Product Specifications

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