STMicroelectronics M41T93SQA6F

Overview

M41T93SQA6F from STMicroelectronics is a serial SPI real-time clock (RTC) with embedded 32.768 kHz crystal, battery switchover circuitry, and integrated alarm, watchdog, and 8-bit timer functions. It operates from 2.0 V to 5.5 V, delivers ±5 ppm factory-calibrated accuracy (SOX18), and maintains timekeeping during main power loss using VBAT backup. Used in industrial control panels for timestamped event logging and power-fail recovery.

For engineers reviewing the M41T93SQA6F datasheet, M41T93SQA6F pinout, M41T93SQA6F application, or M41T93SQA6F equivalent, key selection criteria include ultra-low 365 nA battery current, SPI Mode 0 compatibility, dual programmable alarms with interrupt support in backup mode, and built-in oscillator fail detection - all verified in production-grade SOX18 packaging.

Technical Context

The M41T93SQA6F implements a fully autonomous RTC subsystem: its internal 32.768 kHz oscillator drives BCD-formatted calendar counters (century/year/month/date/hour/minute/second/tenths-hundredths), with automatic leap-year and month-length correction. The device uses dedicated hardware logic-not firmware-to manage clock coherency during register reads/writes, preventing partial updates across multi-byte time fields.

SPI communication follows strict Mode 0 (CPOL = 0, CPHA = 0): SDI latches on SCL rising edge, SDO shifts out on falling edge; E must transition high-to-low before each transaction. Power management includes fixed-reference switchover at VRST = 2.93 V, automatic write protection during VCC recovery (tREC delay), and battery-low flag assertion below VBAT threshold.

Key Specifications

Pinout & Package

Package: SOX18 - 18-lead plastic SOIC (300 mil), 11.61 mm × 7.62 mm, with embedded 32.768 kHz crystal. Requires only external battery connection (VBAT) for full non-volatile operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231SN#T&R and PCF8563T, the M41T93SQA6F uniquely combines SPI interface, embedded crystal, dual alarms, watchdog, and oscillator fail detection in a single SOX18 package - optimizing for industrial reliability, design simplicity, and feature-rich timekeeping without trade-offs in accuracy or power.

Availability

M41T93SQA6F is available at Aetrix Electronics and suitable for industrial data loggers, smart energy meters, medical infusion pumps, and building automation controllers requiring stable component supply across extended product lifecycles.

Supply support for M41T93SQA6F 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and timing solutions for industrial, automotive, and consumer markets.

The M41T93 belongs to ST's precision RTC product line, engineered specifically for applications demanding guaranteed timekeeping integrity during power transitions, long-term battery operation, and minimal external component count - especially where embedded crystal integration improves yield and reliability.

FAQ

What is the function of the DU pin on M41T93SQA6F?

The DU (Do Not Use) pin is an unused terminal in the SOX18 package and must be tied to VCC per the datasheet. It has no internal connection and serves only as a mechanical anchor or thermal pad; leaving it floating or grounding it violates ST's recommended layout and may cause undefined behavior during thermal cycling.

Can the M41T93SQA6F operate without a battery connected?

Yes - VBAT may be tied directly to VSS (ground) if battery backup is not required. In this configuration, the RTC ceases operation when VCC is removed, and all registers reset on next power-up. Battery-low flag and switchover circuitry remain inactive, but all other functions (alarms, SQW, timer) operate normally while VCC is present.

How does the M41T93SQA6F handle leap year calculation?

The M41T93SQA6F automatically adjusts calendar registers for leap years (e.g., February 29, 2024) and variable month lengths (28–31 days) using hardwired logic. This occurs transparently during internal counter increment; no host software intervention is needed, and corrections apply regardless of whether the century bit (CB1:CB0) is set.

Is the SQW output capable of driving an external load directly?

Yes - the SQW pin is a push-pull output (not open-drain) capable of sourcing/sinking ≥2 mA at VCC = 3.3 V. It can directly drive LEDs, small logic inputs, or crystal oscillator enable lines without external buffering; however, capacitive loads >50 pF require series resistance to prevent waveform distortion per Figure 10 in the datasheet.