STMicroelectronics M41T93RQA6F

Overview

M41T93RQA6F from STMicroelectronics is a serial SPI real-time clock (RTC) with integrated 32.768 kHz oscillator, battery switchover circuitry, and 7-byte SRAM. It delivers ±5 ppm factory-calibrated accuracy (SOX18), supports 2.7–5.5 V VCC operation, maintains time across power loss using VBAT, and provides alarm, watchdog, 8-bit timer, and programmable 32 kHz square wave output - deployed in industrial control panels requiring long-term timestamp integrity.

For engineers reviewing the M41T93RQA6F datasheet, M41T93RQA6F pinout, M41T93RQA6F application, or M41T93RQA6F equivalent, key selection criteria include backup-mode alarm persistence, analog/digital calibration capability, IRQ/FT/OUT pin interrupt priority in backup mode, and QFN16 package thermal performance under extended temperature cycling.

Technical Context

The M41T93RQA6F implements a fully autonomous RTC subsystem: its embedded oscillator uses either external crystal (QFN16) or factory-mounted crystal (SOX18), with dual-stage calibration-programmable analog load capacitance (0–12.5 pF in 0.5 pF steps) and digital periodic counter correction (±127 ppm adjustment). The device features dedicated hardware for clock data coherency during register reads, preventing partial updates across BCD-formatted time fields.

Its power management includes fixed-reference switchover at VRST = 2.63 V (R variant), automatic write protection during brown-out recovery (tREC = 250 ms min), and oscillator fail detection with interrupt enable. The IRQ/FT/OUT pin operates as open-drain with configurable priority: alarm > watchdog > timer > oscillator fail > frequency test in VCC mode; alarm retains top priority in backup mode.

Key Specifications

Pinout & Package

Package: QFN16, 4 mm × 4 mm, no-lead, wettable flank - optimized for automated optical inspection and thermal dissipation in dense PCB layouts.

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 M41T93RQA6F uniquely balances SPI compatibility, dual-alarm flexibility, and on-chip calibration - making it optimal for industrial systems needing field-adjustable accuracy and deterministic interrupt behavior in mixed-power environments.

Availability

M41T93RQA6F 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 M41T93RQA6F 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 real-time clock portfolio engineered for high-reliability embedded systems requiring battery-backed timekeeping, deterministic interrupt response, and long-term calibration stability in harsh thermal environments.

FAQ

What is the function of the DU pin on M41T93RQA6F?

The DU (Do Not Use) pin must be tied to VCC per datasheet Figure 3 and Table 1. It is an unused internal test pad with no electrical function; leaving it floating or grounding it may cause undefined behavior or increased leakage current in the QFN16 package.

Does M41T93RQA6F support SPI Mode 3 (CPOL = 1, CPHA = 1)?

No. The M41T93RQA6F supports SPI Mode 0 exclusively (CPOL = 0, CPHA = 0), as confirmed in Section 1.1.3 and Figure 6 of the datasheet. Attempting Mode 3 will result in incorrect data latching on SDI and corrupted SDO output due to mismatched clock edge sampling.

How does the M41T93RQA6F handle leap years and month-end rollovers?

The device automatically adjusts for 28-, 29- (leap year), 30-, and 31-day months using internal BCD arithmetic logic. Leap year calculation follows the Gregorian calendar rule (divisible by 4, except centuries unless divisible by 400), validated across the full –40 °C to +85 °C operating range.

Can the SQW output be disabled or configured to high-impedance state?

No. The SQW pin is a push-pull output with fixed drive strength and no disable control bit. To isolate it, external series resistance or a MOSFET gate driver must be used. The datasheet confirms SQW defaults to 32 kHz on power-up and remains active whenever VCC or VBAT is present.