What Is DS3231S RTC?

What Is DS3231S?
The DS3231 is a highly accurate, low-cost I2C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. It features a battery input to maintain timekeeping during power interruptions, ensuring reliability. Its integrated crystal enhances long-term accuracy and reduces component count, making it suitable for commercial and industrial use in a 16-pin SO package.
This RTC tracks seconds, minutes, hours, day, date, month, and year, with automatic adjustments for shorter months and leap years. It supports 12-hour or 24-hour formats with AM/PM indicators, two programmable alarms, and a square-wave output. The device uses an I2C interface for serial communication. It also includes a voltage reference and comparator to monitor power status, switch to backup power when needed, and provide reset functionality through the RST pin.
Pin Description of DS3231S
Pin 1 - 32kHz: 32kHz output, open-drain requiring external pullup resistor; operates on either power supply. Can be left unconnected if unused.
Pin 2 - VCC: Primary power supply pin; decouple with a 0.1µF to 1.0µF capacitor. Connect to ground if unused.
Pin 3 - INT/SQW: Multifunction pin (interrupt or square wave), open-drain with external pullup to ≤5.5V. Function depends on INTCN bit. Defaults to interrupt output on power-up. Leave unconnected if unused.
Pin 4 - RST: Active-low reset, open-drain with internal 50kΩ pullup. Indicates VCC status, doubles as a debounced pushbutton input. No external pullup needed.
Pins 5-12 - N.C.: No connection, must be grounded.
Pin 13 - GND: Ground connection.
Pin 14 - VBAT: Backup power input; decouple with a low-leakage capacitor if used as primary power source. Ground if unused. UL recognized for lithium battery safety.
Pin 15 - SDA: I2C data input/output, open-drain with external pullup. Supports pullup voltage up to 5.5V.
Pin 16 - SCL: I2C clock input, synchronizes data movement. Pullup voltage up to 5.5V.
Circuit Principle of DS3231S
The circuit principle of the DS3231S is based on a high-precision I2C real-time clock module, with its core components being a temperature-compensated crystal oscillator (TCXO) and an internal crystal. The module generates precise clock signals through the internal oscillator and employs temperature compensation technology to minimize the impact of environmental temperature changes on clock accuracy.
VCC acts as the main power input, with the chip using it when available and switching to VBAT during power loss to maintain timekeeping. The I2C interface enables communication with external devices for time data exchange or settings. The clock output generates a square wave for synchronization, while internal circuitry handles date, month, and leap year adjustments for accurate timekeeping.
Specification of DS3231S
Operating Voltage (VCC): 2.3V ~ 5.5V
Backup Battery Voltage (VBAT): 2.3V ~ 3.7V
Timekeeping Current: 110µA ~ 170µA @ 3.63V ~ 5.5V
Interface: I2C, 2-Wire Serial
Temperature Range (Commercial): 0°C ~ 70°C
Time Format: HH:MM:SS (12/24 hr)
Date Format: YY-MM-DD-dd
Clock Format: 12-hour or 24-hour with AM/PM indicator
Alarms: Two programmable alarms
Package: 16-SOIC
Backup Switchover Time: <1µs
Power Consumption (Timekeeping Mode): 1µA (typical) at VBAT = 3.0V
Features of DS3231S
Highly Accurate RTC Completely Manages All Timekeeping Functions
Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year, with Leap-Year Compensation Valid Up to 2100
Accuracy ±2ppm from 0°C to +40°C
Accuracy ±3.5ppm from -40°C to +85°C
Digital Temp Sensor Output: ±3°C Accuracy
Register for Aging Trim
RST Output/Pushbutton Reset Debounce Input
Two Time-of-Day Alarms
Programmable Square-Wave Output Signal
Simple Serial Interface Connects to Most Microcontrollers
Fast (400kHz) I2C Interface
Battery-Backup Input for Continuous Timekeeping
Low Power Operation Extends Battery-Backup Run Time
3.3V Operation
Operating Temperature Ranges: Commercial (0°C to +70°C) and Industrial (-40°C to +85°C)
Underwriters Laboratories® (UL) Recognized
Where to Use DS3231S?
The DS3231S is ideal for applications requiring high-precision timekeeping and reliability. Its integrated temperature-compensated crystal oscillator ensures accuracy across varying environments, making it well-suited for servers to maintain precise system clocks, telematics systems for accurate data logging and synchronization, utility power meters to record exact usage times, and GPS devices for reliable time reference in navigation systems.
How to Use DS3231S?
The process of using the DS3231S is as follows: First, connect the module to the system circuit, ensuring that the VCC pin is connected to the main power supply and the VBAT pin is connected to a backup power source (such as a coin cell battery) to maintain clock data during power outages. Simultaneously, integrate the I2C bus by connecting the SDA and SCL pins to the corresponding data and clock lines of the host device for data transmission and command reception.
Next, send I2C commands from the host device to set the time or read time data. You may choose to enable square wave output by using the SQW pin to provide synchronization signals to external devices. The module's internal circuitry automatically adjusts the date, month, and leap years without requiring additional calibration. Once these settings are completed, the DS3231S can deliver precise timekeeping and ensure reliable clock functionality.
Package of DS3231S
The DS3231S is housed in a 16-pin SOIC package, offering a compact and reliable form factor. The key dimensions of the 16-SOIC package are as follows:
- Body Width: 7.5 mm.
- Body Length: 10.3 mm.
- Pin Pitch: 1.27 mm.
- Package Height: 2.35 mm.
- Pin Width: 0.41 mm.
This package provides ease of integration into PCB designs, offering sufficient pin spacing for soldering while maintaining a small footprint suitable for various electronic applications.
FAQs
Can the DS3231S output a square wave?
Yes, the DS3231S can generate a square wave output through the SQW pin, which can be used for synchronization with external devices.
How does the DS3231S adjust for leap years and different month lengths?
The DS3231S automatically adjusts for months with fewer than 31 days and accounts for leap years.
How does the DS3231S maintain time during power outages?
The DS3231S has a backup battery (VBAT) that automatically powers the chip when the main power (VCC) fails, ensuring continuous timekeeping.