M41T81S Serial real-time clock (RTC) with alarm

The M41T81S is a low power serial RTC with a built-in 32.768 kHz oscillator (external crystal controlled). Eight bytes of the SRAM are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 12 bytes of SRAM provide status/control of alarm, watchdog and square wave functions. Addresses and data are transferred serially via a two line, bi-directional I²C interface. The built-in address register is incremented automatically after each WRITE or READ data byte.

The M41T81S has a built-in power sense circuit which detects power failures and automatically switches to the battery supply when a power failure occurs. The energy needed to sustain the clock operations can be supplied by a small lithium button supply when a power failure occurs. Functions available to the user include a non-volatile, time-of-day clock/calendar, alarm interrupts, watchdog timer and programmable square wave output. 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 - valid until year 2100), 30 and 31 day months are made automatically.

The M41T81S is supplied in either an 8-pin SOIC or an 18-pin (MY), 300 mil SOIC package which includes an embedded 32 KHz crystal.

The 18-pin, embedded crystal SOIC requires only a user-supplied battery to provide non-volatile operation.

技术特性

Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
32 KHz crystal oscillator with integrated load capacitance (12.5 pf) which provides exceptional oscillator stability and high crystal series resistance operation)
Oscillator stop detection (monitors clock operation)
Serial interface supports I²C bus (400 kHz protocol)
Ultra-low battery supply current of 0.6 μA (typ)
2.0 to 5.5 V clock operating voltage
Automatic switchover and deselect circuitry (fixed reference) which provides full operation in 3.0 V applications)
VCC= 2.7 to 5.5 V
2.5 V ≤ VPFD≤ 2.7 V
Power-down time stamp (HT bit) which allows determination of time elapsed in battery backup
Battery low flag
Programmable alarm and interrupt function (valid even during battery backup mode)
Accurate programmable watchdog timer (from 62.5 ms to 128 s)
Software clock calibration (to compensate for crystal deviation due to temperature)
Operating temperature of –40 to 85 °C
Package options include an 8-lead SOIC or 18-lead embedded crystal SOIC

功能框图

M41T81S 订购信息

订购型号	产品状态	美金价格	数量	封装	包装形式	温度范围	材料声明
M41T81SMY6F	Active			SO-18	Tape And Reel	-40 °C-85°C	M41T81SMY6F
M41T81SMY6E	NRND			SO-18	Tube	-40 °C-85°C	M41T81SMY6E
M41T81SM6F	Active			SO-8	Tape And Reel	-40 °C-85°C	M41T81SM6F

DATASHEET

描述	版本	大小
M41T81S : Serial access real-time clock with alarms	6	525KB

APPLICATION NOTES

描述	版本	大小
AN922: Using a Super Cap to back up the M41T56, M41T00, M41T11, M41T81, M41T81S, and M41ST84W (16-pin)	2	85KB
AN1012: Predicting the battery life and data retention period of NVRAMs and serial RTCs	4	440KB
AN1572: Power-down time-stamp function in serial real-time clocks (RTCs)	2	172KB
AN1216: Implementing a periodic alarm with TIMEKEEPER®	1	55KB
AN934: How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products	4	124KB
AN1011: Battery technology used in NVRAM and real-time clock (RTC) products from ST	4	249KB
AN3060: Applications guide for serial real-time clocks	1	355KB

USER MANUALS

描述	版本	大小
UM0963 : STEVAL-IFS012V1 demonstration board based on multiple temperature sensors and RTCs	1	2214KB