STMicroelectronics M41T64Q6F

Overview

M41T64Q6F from STMicroelectronics is a low-power serial real-time clock (RTC) with integrated 32.768 kHz crystal oscillator, I²C interface (400 kHz), programmable square wave output (1 Hz to 32 kHz), alarm interrupt, and oscillator fail detection. It operates from 1.3 V to 4.4 V, maintains timekeeping down to 1.0 V, and draws only 350 nA at 3 V - enabling multi-year battery backup in portable medical monitors and industrial data loggers.

For engineers reviewing the M41T64Q6F datasheet, M41T64Q6F pinout, M41T64Q6F application, or M41T64Q6F equivalent, key selection considerations include its embedded crystal LCC8 package (1.5 × 3.2 mm), F32K dedicated 32 kHz output, SQW open-drain programmable square wave, and support for automatic leap year compensation and software calibration (±2 ppm).

Technical Context

The M41T64Q6F implements a binary-coded decimal (BCD) RTC core with eight clock/calendar registers (century, year, month, date, day, hour, minute, second, tenths/hundredths), updated via I²C slave address 0xD0h. Its on-chip 32.768 kHz oscillator integrates load capacitors and supports high-series-resistance crystals, eliminating external components.

It features dual timekeeping outputs: F32K (dedicated, always-enabled 32 kHz output) and SQW (open-drain, programmable 1 Hz–32 kHz square wave, defaulting to 32 kHz on power-up). Alarm functionality includes repeat modes and flag enable (AFE), while oscillator fail detection (OF/OFIE) provides fault monitoring without external circuitry.

Key Specifications

Pinout & Package

Package: Ultra-small 1.5 × 3.2 mm, 8-pin ceramic leadless chip carrier (LCC8), ECOPACK2-compliant, with embedded 32.768 kHz crystal - no external oscillator components required.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231SN and PCF8563T, the M41T64Q6F uniquely combines embedded crystal, dual outputs (F32K + SQW), sub-µA timekeeping, and software calibration - making it optimal for space-constrained, long-life battery systems needing both precision and flexibility.

Availability

M41T64Q6F is available at Aetrix Electronics and suitable for industrial data loggers, portable medical monitors, smart utility meters, and automotive telematics units requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for M41T64Q6F 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 analog, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The M41T6x series is part of ST's low-power timing portfolio, engineered specifically for battery-critical applications demanding autonomous, long-duration timekeeping with minimal external components and robust fault monitoring.

FAQ

Does M41T64Q6F require an external crystal?

No. The M41T64Q6F uses an ultra-small 1.5 × 3.2 mm LCC8 package with an embedded 32.768 kHz crystal and integrated load capacitors. This eliminates all external timing components, reducing PCB area, BOM cost, and layout sensitivity - confirmed in ST's DS3840 Rev 24 datasheet Section 1 and Figure 4.

What is the function of the F32K pin?

F32K is a dedicated, always-enabled CMOS-level 32.768 kHz output that drives microcontroller clock inputs directly. Unlike SQW, it cannot be disabled or reprogrammed - it starts immediately on power-up and remains active regardless of register settings, as specified in Table 2 and Figure 5 of DS3840.

How does oscillator fail detection work on M41T64Q6F?

The device continuously monitors oscillator activity and sets the OF (oscillator fail) flag in register 0Fh when oscillation stops. When OFIE is enabled (bit D7 of register 02h), this triggers an interrupt on the IRQ/OUT pin. No external circuitry is needed - detection is fully internal and documented in Section 3.11 of DS3840.

Can M41T64Q6F operate from a single-cell lithium battery?

Yes. With a 1.3 V to 4.4 V operating range and functional timekeeping down to 1.0 V, the M41T64Q6F supports direct connection to single-cell Li-ion (3.0–4.2 V) or LiFePO₄ (2.5–3.65 V) batteries. Its 350 nA current draw at 3 V enables multi-year operation on common coin cells, per Section 3.2 and Table 6 of DS3840.