Features

• 5.0, 3.3, or 3.0 V operation

• 400 kHz I2C bus

• NVRAM supervisor to non-volatize external LPSRAM

• 2.5 to 5.5 V oscillator operating voltage

• Automatic switchover and deselect circuitry

• Choice of power-fail deselect voltages

− M41ST87Y: (not recommended for new design, contact ST sales office for availability) THS = 1: VPFD≈ 4.63 V; VCC = 4.75 to 5.5 V THS = 0: VPFD≈ 4.37 V; VCC = 4.5 to 5.5 V

− M41ST87W: THS = 1: VPFD ≈ 2.9 V; VCC = 3.0 to 3.6 V THS = 0: VPFD ≈ 2.63 V; VCC = 2.7 to 3.6 V

• Two independent power-fail comparators (1.25 V reference)

• Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century

• 128 bytes of clearable, general purpose NVRAM

• Programmable alarm and interrupt function (valid even during battery backup mode)

• Programmable watchdog timer

• Unique electronic serial number (8-byte)

• 32 kHz frequency output available upon power-on

• Microprocessor power-on reset output

• Battery low flag

• Ultra-low battery supply current of 500 nA (typ)

Security features

• Tamper indication circuits with timestamp and RAM clear

• LPSRAM clear function (TPCLR)

• Packaging includes a 28-lead, embedded crystal SOIC and a 20-lead SSOP

• Oscillator stop detection