RTC DS3231 Module Symbol

The RTC DS3231 Module schematic symbol. Standard-specific details are listed below where available.

Definition: The RTC DS3231 Module symbol represents a real-time clock module built around the Maxim DS3231 temperature-compensated crystal oscillator (TCXO) IC, depicted as a rectangular block with VCC, GND, and SDA (I2C data) pins, used in circuit diagrams to indicate a battery-backed precision timekeeping peripheral that maintains accurate date and time independent of the host microcontroller.

Also known as: DS3231 RTC, real-time clock module, I2C RTC, battery-backup clock, DS3231SN module.

What the RTC DS3231 Module symbol means

The RTC DS3231 Module symbol in a circuit diagram represents a self-contained timekeeping module that uses the DS3231 TCXO IC to maintain accurate time (±2 ppm from 0 °C to +40 °C) even when the host system is powered off, using a CR2032 coin-cell backup battery. The module communicates with a microcontroller over I2C using the SDA and SCL lines.

In schematics, the RTC module symbol indicates where persistent time-of-day and date information originates in a system. It is used in data loggers, alarm clocks, scheduled-task controllers, and any embedded design where time must be known accurately across power cycles.

How to identify the RTC DS3231 Module symbol

The RTC DS3231 Module symbol is drawn as a rectangle labelled 'RTC DS3231' or 'RTC Module' with power pins VCC and GND on one edge and I2C signal pins SDA (and often SCL) on the same or opposing edge. Some symbol libraries also show SQW (square-wave/interrupt output) and 32K (32.768 kHz output) pins. The symbol resembles a generic IC block and is distinguished by the 'RTC' or 'DS3231' label and the I2C pin names.

Function and usage boundary

The DS3231 RTC module maintains a running clock (seconds, minutes, hours, day, date, month, year with leap-year compensation) and communicates the current time to a host microcontroller via I2C at address 0x68. The on-chip temperature-compensated oscillator corrects for frequency drift due to temperature changes, achieving ±2 ppm accuracy. A CR2032 backup battery on the module keeps the clock running when main power is removed, preserving time across power cycles for months to years.

Standards: IEC vs ANSI

IEC 60617	IEC 60617 does not define a dedicated symbol for RTC modules. IEC practice represents the module as a functional rectangular block with labelled I2C signal pins per IEC 60617-12.
ANSI/IEEE 315	ANSI/IEEE 315 does not define a specific RTC module symbol. The DS3231 module is represented as a rectangular IC block with VCC, GND, SDA, SCL, SQW, and 32K pin labels following IEEE 315 IC symbol conventions.
Key difference	No IEC vs ANSI standard symbol difference exists for RTC modules. Both standards use a generic IC block representation with labelled pins.

The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.

Logical terminals

Logical ID	Editor terminal name
vcc	VCC
gnd	GND
sda	SDA

Where the RTC DS3231 Module symbol is used

Data loggers — timestamping sensor readings (temperature, humidity, current) stored to SD card or EEPROM
Arduino and Raspberry Pi alarm clock projects requiring accurate time display on an LCD
Scheduled task controllers that activate relays or outputs at specific times of day
Industrial IoT edge devices that must log events with accurate timestamps when internet NTP is unavailable
Battery-powered environmental monitors that record data over weeks and need accurate time alignment for analysis
Home automation systems (ESP32, ESP8266) where time-based rules must persist across Wi-Fi or power outages

Key facts

The DS3231 uses a temperature-compensated crystal oscillator (TCXO) to achieve ±2 ppm accuracy (0–40 °C), far more accurate than the DS1307 (no temperature compensation, ±20 ppm typical).
The I2C address of the DS3231 is fixed at 0x68 (7-bit); only one DS3231 can share an I2C bus without address conflict.
Pin VCC accepts 2.3–5.5 V, making the module compatible with both 3.3 V (ESP32, Raspberry Pi) and 5 V (Arduino Uno) systems without level shifting.
The CR2032 backup battery on the module maintains timekeeping for approximately 8–10 years at room temperature when main power is absent.
The SQW pin outputs a programmable square wave at 1 Hz, 1.024 kHz, 4.096 kHz, or 8.192 kHz, or can be configured as an alarm interrupt output.
The DS3231 module also contains an internal temperature sensor (±3 °C accuracy) accessible over I2C, useful as a secondary ambient temperature reference.
The standard pin designators are VCC (+3.3–5 V), GND, SDA (I2C data), SCL (I2C clock), SQW (square wave/interrupt), and 32K (32.768 kHz output).

Frequently asked questions

What does the RTC DS3231 module symbol mean in a circuit diagram?

The RTC DS3231 module symbol represents a real-time clock module that maintains accurate date and time over I2C and continues running from a CR2032 backup battery when main power is off. The symbol shows where a microcontroller obtains timekeeping data in the circuit.

What does the RTC module symbol look like?

The RTC DS3231 module symbol is a rectangle labelled 'RTC DS3231' or 'RTC Module' with power pins (VCC, GND) and I2C pins (SDA, SCL) on its edges. Some versions show additional pins SQW and 32K. The shape follows the standard IC rectangular block convention used in EDA tools.

What I2C address does the DS3231 use?

The DS3231 has a fixed I2C address of 0x68 (7-bit). This address cannot be changed, so only one DS3231 can be used on a single I2C bus. To use multiple real-time clocks, a different RTC IC with configurable address pins is required.

How accurate is the DS3231 RTC?

The DS3231 achieves ±2 ppm accuracy from 0 °C to +40 °C, equivalent to less than 1 minute of drift per year. Over the full industrial range (−40 °C to +85 °C) accuracy is ±3.5 ppm. This is significantly better than the DS1307 (±20 ppm typical) due to the on-chip temperature-compensated oscillator.

How long does the backup battery last on the DS3231 module?

A standard CR2032 lithium coin cell powering only the DS3231's timekeeping circuit lasts approximately 8–10 years at room temperature. Battery life is reduced if the SQW or 32K outputs are actively loaded, or at elevated temperatures.

What is the difference between DS3231 and DS1307?

The DS3231 includes a temperature-compensated crystal oscillator (TCXO) for ±2 ppm accuracy and operates from 2.3–5.5 V. The DS1307 uses an external 32.768 kHz crystal, achieves ±20 ppm typical, and requires 4.5–5.5 V supply. The DS3231 is the superior choice for accurate timekeeping.

What pins does the RTC DS3231 module have?

The DS3231 module exposes VCC (2.3–5.5 V supply), GND (ground), SDA (I2C data), SCL (I2C clock), SQW (programmable square-wave or alarm interrupt output), and 32K (32.768 kHz auxiliary clock output). Only VCC, GND, SDA, and SCL are needed for basic timekeeping operation.

Related symbols

Physical breadboard, PCB, and panel mapping

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