STMicroelectronics M41T65Q6F

Overview

M41T65Q6F from STMicroelectronics is a low-power serial real-time clock (RTC) IC with integrated 32.768 kHz crystal oscillator, alarm interrupt, watchdog timer output (WDO), and oscillator fail detection. It operates from 1.3 V to 4.4 V, draws only 350 nA in timekeeping mode at 3 V, and maintains timekeeping down to 1.0 V. Its ultra-small 1.5 × 3.2 mm LCC-8 package embeds the crystal - eliminating external components - and targets battery-backed embedded systems requiring precise, autonomous timekeeping.

For engineers reviewing the M41T65Q6F datasheet, M41T65Q6F pinout, M41T65Q6F application, or M41T65Q6F equivalent, key selection criteria include its integrated crystal LCC-8 footprint, open-drain WDO/IRQ/FT/OUT pin for system-level fault signaling, ±2 ppm software calibration capability, and support for I²C-based alarm-triggered wake-up in ultra-low-power microcontroller sleep modes.

Technical Context

The M41T65Q65 implements a binary-coded decimal (BCD) RTC core with eight clock/calendar registers (century, year, month, date, day, hour, minute, second, and tenths/hundredths of second), automatically handling leap-year compensation and month-length corrections. Its on-chip 32.768 kHz oscillator integrates load capacitors and supports high-series-resistance crystals.

It features a dedicated watchdog timer with programmable timeout (62.5 ms to 31 minutes), oscillator fail detection with interrupt enable (OFIE), and a multifunction open-drain IRQ/FT/OUT pin supporting interrupt generation, frequency test mode, and general-purpose output - all controlled via I²C-accessible registers at slave address 0xD0h.

Key Specifications

Pinout & Package

Package: 1.5 × 3.2 mm, 8-pin ceramic leadless chip carrier (LCC-8), ECOPACK2-compliant, with embedded 32.768 kHz crystal - no external XTAL required.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RTC-with-alarm applications.

Compared with DS3231SN#T&R and M41T81Q6F, the M41T65Q6F uniquely combines embedded crystal, dedicated WDO pin, and oscillator fail detection in a 1.5 × 3.2 mm footprint - optimizing for space-constrained, battery-operated systems requiring autonomous fault signaling.

Availability

M41T65Q6F is available at Aetrix Electronics and suitable for smart metering, industrial data loggers, medical wearables, and asset tracking beacons requiring stable component supply, long-life backup operation, and minimal PCB footprint.

Supply support for M41T65Q6F 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, designing and manufacturing microcontrollers, analog ICs, MEMS, and power solutions for industrial, automotive, and consumer markets.

The M41T6x series was developed specifically for ultra-low-power, space-constrained embedded systems needing autonomous, battery-backed timekeeping with integrated timing infrastructure - reducing design risk and bill-of-materials overhead.

FAQ

Does M41T65Q6F require an external crystal?

No. The M41T65Q6F uses an embedded 32.768 kHz crystal inside its 1.5 × 3.2 mm LCC-8 package. No external crystal, load capacitors, or oscillator circuitry is needed - simplifying layout and improving reliability in vibration-prone environments.

What is the function of the IRQ/FT/OUT pin?

The IRQ/FT/OUT pin is a multifunction open-drain output. It serves as alarm interrupt (IRQ), frequency test signal (FT), or general-purpose output (OUT), configurable via register bits. In default alarm mode, it asserts low upon match and can wake a sleeping MCU without polling.

How does the watchdog timer operate independently of I²C?

The watchdog timer runs autonomously from the RTC oscillator and does not depend on I²C communication. Once enabled and configured via register 09h, it times out after a set interval (62.5 ms to 31 min) and drives the dedicated WDO pin low - triggering a hardware reset even if the MCU is unresponsive or I²C is stalled.

Can M41T65Q6F maintain time during main power loss?

Yes. When VCC drops below operating range, the device switches to backup power (e.g., supercapacitor or coin cell on VCC pin). Timekeeping continues down to 1.0 V, and the 350 nA quiescent current enables multi-year operation on typical backup sources without recharge circuitry.