STMicroelectronics M41T93SMY6F

Overview

M41T93SMY6F 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 counter functions. It operates from 2.0 V to 5.5 V, achieves ±5 ppm factory calibration accuracy (SOX18), and draws only 365 nA in battery backup mode. Used in industrial control panels for timestamping event logs during mains failure.

For engineers reviewing the M41T93SMY6F datasheet, M41T93SMY6F pinout, M41T93SMY6F application, or M41T93SMY6F equivalent, key selection criteria include ultra-low backup current, dual-alarm interrupt capability, programmable square wave output, oscillator fail detection, and SRAM retention under battery power.

Technical Context

The M41T93SMY6F implements a fully autonomous RTC subsystem with BCD-encoded calendar registers (century, year, month, date, day, hour, minute, second, tenths/hundredths), automatic leap-year correction, and hardware-based data coherency protection during register reads. Its SPI interface strictly supports Mode 0 (CPOL = 0, CPHA = 0), with SDI latched on SCL rising edge and SDO driven on falling edge.

Power management includes fixed-threshold battery switchover (VSO = VRST = 2.93 V), power-on reset (trec = 250 ms), and oscillator stop detection with interrupt flag. Calibration uses both digital (±127 ppm stepwise correction) and analog (programmable load capacitance) methods, enabling post-reflow accuracy optimization without external components.

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; only VBAT connection needed for 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 PCF2129AT, the M41T93SMY6F uniquely combines SPI interface, embedded crystal, dual alarms, and programmable square wave in a single SOX18 package-making it optimal for cost-sensitive, space-constrained industrial designs requiring flexible timing peripherals.

Availability

M41T93SMY6F 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 temperature ranges and long product lifecycles.

Supply support for M41T93SMY6F 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 specializing in microcontrollers, power management, sensors, and timing solutions for industrial, automotive, and consumer markets.

The M41T93 belongs to ST's precision RTC product line, designed specifically for systems demanding reliable, low-power timekeeping with integrated backup management and flexible alarm/timing peripherals in compact packages.

FAQ

What is the battery switchover voltage threshold for M41T93SMY6F?

The M41T93SMY6F switches to battery power at VRST = VSO = 2.93 V (typical). This fixed threshold is internally generated and does not require external resistor dividers. The device holds address counters and register contents during transition, ensuring no time loss or data corruption.

Does M41T93SMY6F support SPI Mode 3 (CPOL=1, CPHA=0)?

No. The M41T93SMY6F supports SPI Mode 0 only (CPOL = 0, CPHA = 0). Attempting Mode 3 will result in incorrect data sampling on SDI and invalid SDO timing. MCU SPI peripheral must be configured exclusively for Mode 0 to ensure reliable register access.

How is the embedded crystal in the SOX18 package calibrated at manufacture?

Each SOX18 unit undergoes factory calibration for ±5 ppm accuracy after two reflow cycles. Calibration values are stored in OTP memory and applied automatically at power-up. Analog (load capacitance) and digital (counter offset) trim registers remain accessible for field fine-tuning if higher accuracy is required.

Can the 7-byte user SRAM retain data during VCC brownout if VBAT is present?

Yes. The 7-byte SRAM is powered directly by VBAT during backup mode and retains full data integrity as long as VBAT ≥ 1.5 V. Data remains valid across power cycles and is accessible immediately after VCC restoration, with no initialization delay or refresh requirement.