STMicroelectronics M41T01M6F

Overview

M41T01M6F from STMicroelectronics is a low-power serial real-time clock (RTC) IC with integrated battery switchover circuitry, 32.768 kHz crystal oscillator interface, and I²C-compatible 2-wire serial bus. It maintains timekeeping across power loss via automatic VCC-to-VBAT switchover, supports BCD-formatted calendar registers (seconds to century), and delivers ultra-low 800 nA battery supply current. Used in industrial control panels for timestamped event logging under intermittent mains power.

For engineers reviewing the M41T01M6F datasheet, M41T01M6F pinout, M41T01M6F application, or M41T01M6F equivalent, key selection considerations include its software-calibratable ±2 ppm accuracy at 25 °C, open-drain FT/OUT pin for calibration or general-purpose output, battery-capacitor backup flexibility, and SO8 package compatibility with legacy board layouts.

Technical Context

The M41T01M6F operates as an I²C slave device with fixed 7-bit address 0xD0h, supporting sequential read/write of eight BCD registers (seconds through control). Its internal voltage sense circuit triggers automatic switchover to VBAT when VCC drops below VSO (typically 2.0 V), disabling bus access and entering ultra-low-power data retention mode.

Timekeeping relies on a 32.768 kHz external crystal with no load capacitors required; calibration is implemented via five-bit signed register (D4–D0 in Addr 7) that inserts or removes oscillator cycles every 64 minutes-enabling ±5.5 min/month total adjustment range. The FT/OUT pin serves dual roles: 512 Hz test output (FT=1) or programmable open-drain output (FT=0, OUT bit controlled).

Key Specifications

Pinout & Package

The M41T01M6F is housed in an 8-lead plastic small outline (SO8) package, compliant with JEDEC MS-012AC, with 1.27 mm pitch and 5.0 mm × 4.0 mm body dimensions.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock applications.

Compared with DS1307+ and PCF8563, the M41T01M6F uniquely combines factory-trimmed ±2 ppm accuracy, integrated crystal driver, and dual-mode FT/OUT pin - delivering higher timekeeping fidelity with lower layout risk and fewer external components.

Availability

M41T01M6F is available at Aetrix Electronics and suitable for industrial data loggers, smart energy meters, factory HMI panels, and medical diagnostic devices requiring stable component supply across extended product lifecycles.

Supply support for M41T01M6F 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 M41T01 series belongs to ST's precision timing portfolio, engineered specifically for battery-backed real-time clock applications demanding high accuracy, low power, and robust power-fail resilience in harsh industrial environments.

FAQ

Can the M41T01M6F operate without an external crystal?

No. The M41T01M6F requires an external 32.768 kHz quartz crystal connected between OSCI and OSCO pins. It contains no internal resonator or RC oscillator; the crystal is essential for timekeeping function. The oscillator circuit is designed to drive standard fundamental-mode crystals without load capacitors, but the crystal itself is mandatory.

What happens to the clock registers during VCC-to-VBAT switchover?

During switchover, the M41T01M6F immediately disables I²C bus access, halts register updates, and enters ultra-low-power retention mode. All eight BCD clock/calendar registers retain their values intact. No data corruption occurs because write protection activates before VCC drops below functional threshold, preserving time and date across power loss.

Is capacitor backup supported instead of a battery?

Yes. The M41T01M6F supports capacitor backup on VBAT, especially recommended for 3.0 V systems where lithium coin cells are discouraged. A typical 0.47 F supercapacitor charged via a diode/resistor network provides ~24 hours of backup at 800 nA drain - sufficient for short outages and enabling RoHS-compliant designs.

How is the ±2 ppm calibration achieved in practice?

Calibration is performed by writing a signed 5-bit value (0–31) to bits D4–D0 of the Control Register (Addr 7), where D5 is the sign bit. Each step adjusts timebase by ±2.034 ppm (negative) or ±4.068 ppm (positive) over a 64-minute cycle. Field calibration uses the FT/OUT pin's 512 Hz output to measure actual oscillator error and compute the required correction value.