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The M41T6x is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz oscillator. Eight registers are used for the clock/calendar function and are configured in binary-coded decimal (BCD) format. An additional eight registers provide status/control of alarm, 32 KHz output, calibration, and watchdog functions. Addresses and data are transferred serially via a two-line, bidirectional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte.
Functions available to the user include a time-of-day clock/calendar, alarm interrupts (M41T62/65), 32 KHz output (M41T62/64), programmable square wave output (M41T62/64), and watchdog output (M41T65). The eight clock address locations contain the century, year, month, date, day, hour, minute, second and tenths/hundredths of a second in 24-hour BCD format. Corrections for 28-, 29- (leap year), 30- and 31-day months are made automatically.
The M41T6x is supplied in two very small packages: a tiny, 3 x 3 mm 16-pin QFN which requires a user-supplied 32 KHz crystal, and an ultra-small 1.5 x 3.2 mm LCC with embedded crystal - no external crystal is required.
Key Features
- Serial real-time clock (RTC) with alarm functions
- 400 kHz I2C serial interface
- Memory mapped registers for seconds, minutes, hours, day, date, month, year, and century
- Tenths/hundredths of seconds register
- 350 nA timekeeping current at 3 V
- Timekeeping down to 1.0 V
- 1.3 V to 4.4 V I2C bus operating voltage
- 4.4 V max VCCsuitable for lithium-ion battery operation
- Low operating current of 35 μA (at 400 kHz I2C speed)
- 32 KHz square wave output is on at power-up. Suitable for driving a microcontroller in low-power mode. Can be disabled. (M41T62/64)
- Programmable 1 Hz to 32 KHz square wave output (M41T62/64)
- Programmable alarm with interrupt function (M41T62/65)
- 32 KHz crystal oscillator integrates crystal load capacitors, works with high series resistance crystals
- Oscillator stop detection monitors clock operation
- Accurate programmable watchdog
- 62.5 ms to 31 min timeout
- Software clock calibration. Can adjust timekeeping to within ±2 parts per million (±5 seconds per month)
- Automatic leap year compensation
- –40 to +85 °C operation
- Two package options:
- Very small 3 x 3 mm, lead-free & halogen-free (ECOPACK2®) 16-lead QFN
- Ultra-small 1.5 x 3.2 mm, lead-free & halogen-free (ECOPACK2®) 8-pin ceramic leadless chip carrier with embedded 32 KHz crystal - no external oscillator components required (M41T62)
Circuit Diagram
Resources
Technical Documentation
| Description | Version | Size | |
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DS3840: Low-power serial real-time clocks (RTCs) with alarm | 22.0 | 955 KB |
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AN3060: Applications guide for serial real-time clocks (RTCs) | 3.0 | 878 KB |
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AN1011: Battery technology used in NVRAM and real-time clock (RTC) products from ST | 4.0 | 248 KB |
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AN934: How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products | 4.1 | 123 KB |
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AN1216: Implementing a periodic alarm with TIMEKEEPER® and serial real-time clocks (RTCs) | 2.0 | 192 KB |
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AN4641: Integrating TIMEKEEPER® and real-time clock supervisor functions | 1.0 | 479 KB |
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AN923: Managing century information using serial real-time clocks and TIMEKEEPER® NVRAMs | 4.0 | 142 KB |
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AN1572: Power-down time-stamp function in serial real-time clocks (RTCs) | 2.0 | 171 KB |
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AN1336: Power-fail comparator for NVRAM supervisory devices | 2.0 | 127 KB |
Publications and Collaterals
| Description | Version | Size | |
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Serial real-time clock ICs | 1.0 | 827 KB |
| Description | Version | Size | |
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Smart watches and fitness bands benefit from the ultra-small date/time chip from STMicroelectronics | 1.0 | 160 KB |
Quality & Reliability
| Part Number | RoHS Compliance Grade | Material Declaration** |
|---|---|---|
| M41T62LC6F | Ecopack2 |
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| M41T62Q6F | Ecopack2 |
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(**) The Material Declaration forms available on st.com may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.