DS3231S# - Accurate I2C RTC with TCXO | Analog Devices
MPN: DS3231S# ✓ ActiveDS3231S# Overview
A real-time clock is a clock-and-calendar integrated circuit that retains date and time information while a system is unpowered. The RTC belongs to the timekeeping and clock-and-timing hierarchy within semiconductor electronics. Unlike a general-purpose microcontroller timer, the DS3231S# is designed to maintain calendar information, provide a programmable square-wave output, and interface through a two-wire I2C bus.
The DS3231S# combines a battery-backed RTC, an integrated temperature-compensated crystal oscillator, and an integrated crystal in one package. Its operating-voltage range of 2.3 V to 5.5 V supports both 3.3 V and 5 V systems. The two-wire interface reduces the number of host-controller connections required for timekeeping, while the integrated backup-battery path allows continued operation during a main-power loss.
According to the Analog Devices manufacturer product page, the device is a low-cost, extremely accurate I2C real-time clock with an integrated TCXO and crystal. This integration supports compact designs for industrial controllers, embedded products, data-acquisition equipment, and consumer electronics. The device also provides a 32.768 kHz square-wave output according to the manufacturer datasheet, allowing it to serve as a timebase or clock source for additional system functions.
DS3231S# is appropriate when calendar accuracy, backup timekeeping, and a compact integrated crystal matter more than implementing a software-disciplined oscillator. Designers should provide the required decoupling and maintain suitable routing around the integrated crystal and TCXO. Because the verified source material does not provide a complete pin-by-pin mapping or numeric accuracy and temperature-drift tables, those details should be confirmed in the manufacturer datasheet before schematic release.
This page combines verified manufacturer and distributor information, structured technical guidance, and a comparison framework for engineers evaluating the DS3231S#. It does not infer missing electrical limits, lifecycle claims, or alternative-device specifications that are absent from the supplied source data.
Drop-in alternatives for DS3231S# — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with DS3231S# (same form factor and footprint) — differing in Mounting Type, Package, Product Type.
DS3231SN#
✅ Drop-InContact for price
View Datasheet →DS3231S# Specifications
| Product Type | I2C real-time clock with integrated TCXO and crystal |
| Operating Voltage Range | 2.3 V to 5.5 V |
| Interface | I2C, 2-wire serial |
| Timekeeping Format | Date/month/year and hour/minute/second |
| Integrated Time Base | 32.768 kHz temperature-compensated crystal oscillator and crystal |
| Square-Wave Output | 32.768 kHz |
| Package | 16-SOIC, 7.50 mm width |
| Mounting Type | Surface mount |
| Battery Backup | Integrated battery input for continued timekeeping |
| Main-Power Interruption Handling | Maintains accurate timekeeping during main-power interruption |
| Oscillator Compensation | Temperature-compensated crystal oscillator |
| Crystal Integration | Crystal integrated in the package |
DS3231S# 16-soic, 7.50 mm width Pin Configuration Guide
Pin configuration for DS3231S# (16-soic, 7.50 mm width package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for DS3231S#.
Refer to the datasheet for full pin configuration.
Typical Applications
DS3231S# is suitable for 6 applications: Industrial Data-Acquisition Systems, Battery-Backed Embedded Controllers, Networked IoT Gateways, Precision Test and Measurement Equipment, Automated Access and Attendance Systems, Consumer Electronics and Appliances.
Industrial Data-Acquisition Systems
The DS3231S# fits industrial data-acquisition systems that need timestamps which remain meaningful through brief power interruptions. Its 2.3 V to 5.5 V operating range accommodates common embedded supply rails, while the integrated 32.768 kHz temperature-compensated crystal oscillator and crystal reduce external timing-component count. The I2C interface lets a controller read calendar and clock registers without occupying many general-purpose I/O pins. According to the Analog Devices manufacturer product page, the integrated TCXO and crystal enhance long-term accuracy. Engineers should still verify the qualified temperature range, backup-current demand, and battery-life calculations against the manufacturer datasheet before deploying the RTC in long-duration field installations.
Recommended
Battery-Backed Embedded Controllers
The DS3231S# is well suited to battery-backed embedded controllers because it includes a battery input and maintains timekeeping when main power is interrupted. The verified manufacturer material identifies this behavior as a core function of the device. A host such as an STM32 microcontroller can read and write the clock through I2C while the backup source preserves the time base during resets or power cycling. The 2.3 V minimum supply supports lower-voltage systems, although the exact backup-current and battery-life figures must be confirmed in the manufacturer datasheet. Designers should also verify that the selected battery chemistry and charging arrangement are compatible with the device's battery input.
Recommended
Networked IoT Gateways
The DS3231S# can provide a stable local calendar reference for IoT gateways that must timestamp events, synchronize downstream equipment, or retain time through network interruptions. Its integrated temperature-compensated oscillator and crystal simplify the timekeeping subsystem compared with a discrete crystal design, while I2C provides a compact connection to an application processor. The 2.3 V to 5.5 V range offers flexibility between 3.3 V and 5 V host rails. Because the verified data does not specify long-term drift figures, calibration performance, or environmental limits, gateway designs should use the official datasheet values and evaluate enclosure temperature behavior before relying on the RTC for compliance-grade timestamps.
Recommended
Precision Test and Measurement Equipment
The DS3231S# is useful in test and measurement equipment that records the date and time of samples, calibration events, or diagnostic runs. Its integrated TCXO and crystal provide a compact alternative to an external oscillator network, and the I2C interface allows a measurement controller to synchronize multiple instruments through software. The 32.768 kHz square-wave output can also serve system timing functions where supported. Exact RTC accuracy and drift must be taken from the manufacturer datasheet because those numerical values are not present in the verified excerpts. For laboratory-grade traceability, verify calibration, aging, temperature behavior, and synchronization requirements against the system specification.
Recommended
Automated Access and Attendance Systems
The DS3231S# fits access-control and attendance terminals that need a date and time independent of network time. Backup capability preserves the clock during maintenance or short outages, while the integrated crystal and TCXO reduce component count compared with a discrete oscillator implementation. The I2C interface supports low-pin-count access to the RTC, leaving controller I/O available for displays, readers, and communication. The DS3231S# should not be treated as a security credential or anti-tamper mechanism by itself. For deployments subject to regulatory timekeeping rules, verify the exact accuracy, operating-temperature range, battery behavior, and any external synchronization requirements in the manufacturer datasheet.
Recommended
Consumer Electronics and Appliances
The DS3231S# can support calendar functions, timers, and event logging in consumer electronics and appliances where wall-clock time must survive a power interruption. Its integrated 32.768 kHz TCXO and crystal reduce assembly requirements, and the 2.3 V to 5.5 V range supports both common logic voltages. A host microcontroller reads the time over I2C and applies user-facing scheduling or diagnostic logic. The backup source must be selected for the required service life and safety environment, while exact current consumption and environmental limits remain to be verified in the official datasheet. Cost-sensitive designs should also compare the verified price and availability of the exact ordering suffix.
Recommended
Recommended Products Summary
Engineering reference data for DS3231S# — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | DS3231SN# |
|---|---|---|
| Brand | Analog Devices | Analog Devices |
| Package | 16-SOIC, 7.50 mm width | 16-pin SOIC - same |
| Product Type | I2C real-time clock with integrated TCXO and crystal | I2C-integrated RTC/TCXO/crystal |
| Interface | I2C, 2-wire serial | I2C |
| Integrated Time Base | 32.768 kHz temperature-compensated crystal oscillator and crystal | Integrated RTC/TCXO/crystal |
Key Differentiators
- Integrated temperature-compensated time base (vs DS3231SN#)
- Wide embedded supply compatibility (vs DS3231SN#)
- Compact two-wire timekeeping interface (vs DS3231SN#)
- Main-power interruption resilience (vs DS3231SN#)
Design Notes
Place the DS3231S# close to the host MCU's I2C pins and route SDA and SCL away from switching-regulator inductors, high-current traces, and crystal oscillators. Place the manufacturer's recommended bypass capacitors close to the supply and ground pins, with short ground returns. The integrated crystal does not remove the need for careful layout: preserve the device's recommended footprint, avoid copper or metal structures beneath the crystal area if prohibited by the datasheet, and keep assembly and cleaning processes from applying mechanical stress to the package.
Design the main and backup supplies so that battery-backed operation is not unintentionally disabled during normal power transitions. Confirm the exact battery-pin voltage, charging behavior, and backup-current limits in the Analog Devices datasheet. Estimated backup life should be calculated from the selected cell capacity, conversion efficiency, and the device's measured or specified backup current rather than from nominal capacity alone. Use a suitable protection scheme if the backup source can be reverse charged or shorted, and ensure the main rail cannot backfeed the battery input.
Follow the manufacturer's recommended land pattern and pin-1 orientation for the 16-SOIC package rather than inferring the footprint solely from the 7.50 mm body width. Keep the backup-battery connection and I2C routing away from antenna keepouts and high-voltage isolation boundaries where applicable. Because the complete pinout was not present in the supplied excerpts, verify every net against the official datasheet before PCB release. A symbol-and-footprint review should explicitly check I2C address straps, ground pins, square-wave output, and any oscillator-output or supply pins.
Do not treat DS3231S#, DS3231SN#, and the DS3231S#T&R tape-and-reel ordering code as interchangeable procurement labels without checking the manufacturer ordering information. The hash and suffix can identify package, temperature, and delivery configuration, while T&R identifies tape-and-reel packaging. Likewise, two 16-SOIC RTCs are not automatically register-compatible: verify the I2C address, calendar and alarm registers, square-wave output behavior, battery handling, and interrupt polarity. These checks prevent a mechanically similar but functionally incompatible substitution.
Compliance Information
The supplied manufacturer and distributor records do not explicitly state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. AEC-Q100 is marked not_applicable because no automotive qualification is stated and the device is a general-purpose clock-and-timing IC; this is not an automotive qualification claim.
