STMicroelectronics | M41T81SMY6F

It has 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.

Features:

• 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