Analog Devices Inc./Maxim Integrated DS3234SN#

Overview

DS3234SN# from Maxim Integrated is an extremely accurate SPI bus real-time clock (RTC) with integrated temperature-compensated crystal oscillator (TCXO), 32.768kHz output, 256 bytes of battery-backed SRAM, and power-fail monitoring. It maintains timekeeping accuracy of ±2 ppm (0°C to +40°C) and ±3.5 ppm (−40°C to +85°C), supports 12/24-hour format with leap-year compensation through 2099, and operates from 2.0V to 5.5V VCC with backup via VBAT (2.0V–3.8V). It is used in utility meters, GPS modules, and industrial telemetry systems requiring long-term timing stability without external crystal calibration.

For engineers reviewing the DS3234SN# datasheet, DS3234SN# pinout, DS3234SN# application, or DS3234SN# equivalent, this page delivers verified technical context-including TCXO architecture, alarm register mapping, RST pushbutton debouncing behavior, VCC-to-VBAT switchover timing, and SRAM retention under backup power-to support schematic integration, firmware register initialization, and fail-safe reset design in embedded timing-critical systems.

Technical Context

The DS3234SN# implements a closed-loop TCXO using an on-die temperature sensor, lookup-table-based capacitance tuning, and aging-trim register (0x10–0x11) to maintain ±2 ppm accuracy across 0°C to +40°C. Its RTC core runs independently of the SPI interface and retains full functionality-including alarm matching, 32kHz output, and calendar updates-during VCC dropout and VBAT-only operation.

Power control logic monitors VCC against programmable power-fail threshold (VPF = 2.45–2.70 V); when VCC falls below VPF, RST asserts low for 250 ms and disables SPI access if VCC also drops below VBAT. The INT/SQW pin functions as either open-drain interrupt (alarm-triggered) or programmable square-wave output (1Hz–8.192kHz), selected by INTCN bit in Control Register (0x0E).

Key Specifications

Pinout & Package

DS3234SN# is housed in a 300-mil, 20-pin SOIC package (JEDEC MS-013AC) with exposed pad not electrically connected. Pin 1 is CS (active-low chip select); pins 2 and 7–14 are no-connect (must be grounded); pins 18 and 20 are internally bonded SCLK inputs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock applications.

Compared with DS3234SN#, DS3231SN# offers identical accuracy but sacrifices SPI compatibility and SRAM, while RV-3028-C7 trades precision and programmability for lower cost and I²C simplicity-making DS3234SN# the sole choice for SPI-based industrial systems demanding both high accuracy and persistent memory.

Availability

DS3234SN# is available at Aetrix Electronics and suitable for smart metering, GPS holdover timing, industrial telematics, and medical data logging requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for DS3234SN# includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and timing ICs for industrial, automotive, and communications infrastructure.

The DS3234SN# belongs to Maxim's ultra-accurate RTC product line, engineered specifically for applications where crystal aging, temperature-induced drift, and power-loss resilience directly impact system certification, regulatory compliance, and field reliability.

FAQ

What is the guaranteed accuracy specification for DS3234SN# over its full industrial temperature range?

The DS3234SN# guarantees ±3.5 ppm frequency stability from −40°C to +85°C, measured against nominal 32.768 kHz output. This translates to a maximum cumulative time error of ±1.1 minutes per year under worst-case thermal conditions, validated per Maxim's production test flow and documented in the Electrical Characteristics table (Rev 4, p.3). DS3234SN# achieves this via factory-calibrated TCXO compensation and on-die temperature sensing-not external circuitry.

How does DS3234SN# handle power transitions between VCC and VBAT, and what happens to SPI access during that switch?

When VCC drops below VPF (2.45–2.70 V), DS3234SN# asserts RST low and-only if VCC also falls below VBAT-disables all SPI read/write access to protect register integrity. Timekeeping, alarms, and 32kHz output continue uninterrupted on VBAT. SPI access resumes only after VCC rises above both VPF and VBAT and RST deasserts (tREC = 125–300 ms). This behavior is defined in Table 1 (Power Control) and prevents corrupted register writes during brownout.

Can DS3234SN# operate without an external pullup resistor on the INT/SQW pin, and what are the voltage limits for that pullup?

Yes-DS3234SN#'s INT/SQW pin is open-drain and requires no external pullup if unused. When enabled as interrupt or square-wave output, it supports external pullup voltages up to 5.5 V regardless of VCC level, allowing direct interfacing with 5 V logic or mixed-voltage systems. This is explicitly stated in the Pin Description (p.8): "The pullup voltage can be up to 5.5V, regardless of the voltage on VCC."

What is the function of the RST pin beyond power-fail indication, and how is pushbutton reset debounced in DS3234SN#?

DS3234SN#'s RST pin serves dual roles: (1) open-drain power-fail indicator (driven low when VCC < VPF), and (2) debounced pushbutton input. Upon detecting a falling edge, DS3234SN# pulls RST low for 250 ms (PBDB), then monitors for release; upon rising edge, it holds RST low for another 250 ms (tRST) before releasing. This eliminates mechanical switch bounce without MCU firmware involvement-detailed in the Pushbutton Reset Timing diagram (p.5).

Does DS3234SN# support automatic leap-year correction, and through which year is the calendar valid?

Yes-DS3234SN# automatically adjusts end-of-month dates, including February in leap years, using built-in calendar logic. Its date calculation is valid through year 2099, as confirmed in the General Description (p.1): "leap year compensation valid up to 2099." The century bit (bit 7 of month register) toggles at year overflow (99→00), enabling correct handling of 2100 (non-leap) without firmware intervention.