STMicroelectronics M41T93RMY6F

Overview

M41T93RMY6F from STMicroelectronics is a serial SPI real-time clock (RTC) with integrated 32.768 kHz oscillator, battery switchover circuitry, and 7 bytes of battery-backed SRAM. It delivers ±5 ppm factory-calibrated accuracy (SOX18), ultra-low 365 nA battery supply current, and operates across 2.7 V to 5.5 V VCC. Used in industrial control panels for time-stamped event logging under intermittent power.

For engineers reviewing the M41T93RMY6F datasheet, M41T93RMY6F pinout, M41T93RMY6F application, or M41T93RMY6F equivalent, key selection criteria include backup-mode alarm interrupt persistence, programmable analog/digital calibration, watchdog timer independence from main supply, and SQW output frequency configurability (32.768 kHz default).

Technical Context

The M41T93RMY6F implements a BCD-encoded calendar engine supporting century-aware date arithmetic (leap-year correction, month-end rollover) and dual programmable alarms with interrupt assertion during battery backup mode. Its SPI interface strictly supports Mode 0 (CPOL = 0, CPHA = 0), with chip enable (E) controlling slave selection and automatic address increment on sequential reads/writes.

Power management includes autonomous VCC-to-VBAT switchover at VRST = 2.63 V (R-grade), oscillator fail detection with interrupt enable, and a dedicated open-drain RST output asserting on power-on reset. The 8-bit countdown timer uses selectable clock sources (244.1 μs to 4.25 hrs) and generates interrupts independent of main supply status.

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 PCF8563T, the M41T93RMY6F uniquely combines SPI compatibility, dual backup-mode alarms, on-chip analog/digital calibration, and embedded crystal in SOX18-enabling robust, self-contained RTC functionality without external timing components or interface translation.

Availability

M41T93RMY6F 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 M41T93RMY6F 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, and precision analog ICs, with strong focus on industrial, automotive, and IoT applications.

The M41T93 belongs to ST's real-time clock portfolio designed for high-reliability, battery-backed timekeeping in harsh environments-emphasizing low-power operation, autonomous power switchover, and field-calibratable accuracy.

FAQ

What is the function of the DU pin on M41T93RMY6F?

The DU (Do Not Use) pin is reserved and must be tied to VCC. It has no electrical function and is not connected internally. Leaving it floating or grounding it may cause undefined behavior per STMicroelectronics' datasheet Section 1.1.4 and Figure 3. This requirement ensures proper internal biasing and avoids potential noise coupling into the oscillator circuit.

How does the M41T93RMY6F handle leap year calculation?

The M41T93RMY6F automatically corrects for leap years by evaluating the year value in its BCD-encoded calendar registers. When the date reaches February 28, the device increments to February 29 in leap years (divisible by 4, excluding century years not divisible by 400) and to March 1 otherwise. This logic is hardwired in the calendar engine and requires no firmware intervention.

Can the SQW output be disabled or reconfigured to other frequencies?

Yes-the SQW output can be disabled by clearing the SQWE bit in the square wave register (address 0x14). It supports four programmable frequencies: 32.768 kHz (default), 1.024 kHz, 32 Hz, and 1 Hz. Configuration is performed via SPI write to the SQW register; no external components are needed, and settings persist through power cycles.

What happens to the alarm interrupt during battery backup mode?

The alarm interrupt remains fully functional during battery backup mode: IRQ/FT/OUT asserts when alarm conditions match, even with VCC removed. This behavior is guaranteed by the device's autonomous backup power path and is confirmed in Section 3.5 and Figure 15 of the datasheet. No host MCU intervention is required to maintain alarm responsiveness.