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