M41T81S

概要

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製品概要

概要

The M41T81S is a low-power serial real-time clock (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, bidirectional 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 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.

特徴
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)

V_CC= 2.7 to 5.5 V
2.5 V ≤ V_PFD≤ 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
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