The DS3231 is a low-cost, high-accuracy 12-bit real-time clock (RTC) featuring an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input terminal, enabling timekeeping to persist when the main power supply is disconnected. The integrated crystal enhances the device’s long-term accuracy and reduces the number of components required in production lines. The DS3231 offers commercial and industrial temperature ranges and is housed in a 16-pin 300MIL SO package. The RTC stores seconds, minutes, hours, day of the week, date, month, and year information. For months with fewer than 31 days, the end-of-month date is automatically adjusted, including leap year correction. The clock’s operating format can be either 24-hour or 12-hour with AM/PM indication. Two programmable calendar alarms and one programmable square wave output are provided. Address and data are transmitted serially via a 12C bidirectional bus. A temperature-compensated voltage reference and comparator circuitry monitor the VCC status, detect power supply faults, provide a reset output, and automatically switch to a backup power supply when necessary. Additionally, the /RST monitor pin can serve as a manual input to generate an MP reset.
Beyond its high timing accuracy, the DS3231 incorporates additional features that expand the host system’s functionality and options. An extremely accurate digital temperature sensor is integrated internally, accessible via the I²C* interface (similar to the time function). This temperature sensor achieves an accuracy of ±3°C. On-chip control circuitry enables automatic power detection and manages power switching between the main power supply and the backup power source (i.e., the low-voltage battery). Should the main power supply fail, the device continues to provide timing and temperature functions without performance degradation. When the main power supply is restored or the voltage returns to an acceptable range, the on-chip reset function can be used to restart the system microprocessor.

1. Dimensions: 38mm (length) × 22mm (width) × 14mm (height)
2. Weight: 8g
3. Operating voltage: 3.3–5.5V
4. Clock chip: High-precision DS3231 clock chip
5. Clock accuracy: Within 0–40°C, accuracy 2PPM, annual error approximately 1 minute
6. Features two calendar alarms
7. Programmable square wave output
8. Real-time clock generates seconds, minutes, hours, day of the week, date, month, and year timing, with leap year compensation valid until 2100
9. Integrated internal temperature sensor with accuracy of ±3°C
10. Storage chip: AT24C32 (32K storage capacity)
11. I²C bus interface, high transmission speed 400kHz (at 5V operating voltage)
12. Supports cascading with other I²C devices; 24C32 address modifiable via shorting A0/A1/A2 pins; default address 0x57