STMicroelectronics M41T93ZQA6F

Overview

M41T93ZQA6F from STMicroelectronics is a serial SPI real-time clock (RTC) with embedded 32.768 kHz crystal, battery switchover circuitry, and integrated oscillator fail detection. It delivers ±5 ppm factory-calibrated accuracy (SOX18), ultra-low 365 nA battery supply current, and operates across 2.38 V to 5.50 V VCC. Used in industrial control panels for time-stamped event logging and power-loss-resilient scheduling.

For engineers reviewing the M41T93ZQA6F datasheet, M41T93ZQA6F pinout, M41T93ZQA6F application, or M41T93ZQA6F equivalent, key selection criteria include backup-mode alarm interrupt persistence, programmable analog/digital calibration registers, SQW output frequency configurability, and VSO = VRST = 2.32 V switchover threshold.

Technical Context

The M41T93ZQA6F implements a fully autonomous RTC subsystem with BCD-formatted calendar counters (century, year, month, date, day, hour, minute, second, tenths/hundredths), dual programmable alarms, and a watchdog timer-all accessible via SPI Mode 0 (CPOL = 0, CPHA = 0). Its internal oscillator monitoring detects crystal stoppage and asserts IRQ/FT/OUT accordingly.

Power management includes automatic VCC-to-VBAT switchover at 2.32 V, write protection during brown-out recovery (tREC delay), and battery low flag detection. The device supports 7 bytes of battery-backed SRAM and features an 8-bit countdown timer with selectable source clocks (244.1 μs to 4.25 hrs).

Key Specifications

Pinout & Package

Package: SOX18 - 18-lead plastic SOIC (300 mil), 11.61 × 7.62 mm, with embedded 32.768 kHz crystal. No external crystal required.

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 M41T93ZQA6F uniquely combines SPI interface, embedded crystal, dual alarms with backup-mode operation, oscillator fail detection, and field-programmable calibration-making it optimal for industrial systems requiring robust timekeeping autonomy and diagnostic visibility.

Availability

M41T93ZQA6F 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 M41T93ZQA6F 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 ICs, sensors, and timing solutions for industrial, automotive, and consumer markets.

The M41T93 belongs to ST's precision RTC product line, engineered for applications demanding battery-backed timekeeping with diagnostic integrity, switchover reliability, and field-calibration capability in harsh environments.

FAQ

What is the function of the DU pin on M41T93ZQA6F?

The DU (Do Not Use) pin is a no-connect terminal that must be tied to VCC per the datasheet. It serves no electrical function and is reserved for future package variants. Leaving it floating may cause undefined behavior or increased leakage current; hard connection to VCC ensures stable internal biasing and meets SOX18 mechanical layout requirements.

Can the M41T93ZQA6F operate without an external battery?

Yes - VBAT may be tied directly to VSS (ground) if battery backup is not required. In this configuration, the RTC halts when VCC drops below VSO (2.32 V), and calendar registers reset on next power-up. All other functions (alarms, SQW, timer) remain operational while VCC is valid, but timekeeping continuity across power cycles is lost.

How does the M41T93ZQA6F handle leap year calculation?

The M41T93ZQA6F performs fully autonomous leap year correction in hardware: it advances from February 28 to March 1 in non-leap years, and from February 29 to March 1 in leap years (divisible by 4, except century years not divisible by 400). This logic applies regardless of MCU firmware state and persists through battery backup mode.

Is the SQW output configurable to frequencies other than 32.768 kHz?

Yes - the SQW pin can be programmed to output 32.768 kHz (default), 1.024 kHz, or 1 Hz via the square wave register (address 0x14). All outputs are open-drain and require an external pull-up resistor. Frequency selection is retained across power cycles and remains active in battery backup mode.