Summary description

The M41T94 is a Serial Real Time Clock with 44 bytes of NVRAM and a RESET output. A built-in 32,768Hz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 4 on page 19) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format.

An additional 12 bytes of RAM provide status/control of Alarm, Watchdog and Square Wave functions. Addresses and data are transferred serially via a serial SPI interface. The built-in address register is incremented automatically after each WRITE or READ data byte. The M41T94 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 SRAM and clock operations can be supplied by a small lithium button-cell 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.

Feature summary

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

■ 32KHz crystal oscillator integrating load capacitance (12.5pF) providing exceptional oscillator stability and high crystal series resistance operation

■ Serial peripheral interface (2MHz SPI)

■ Ultra-low battery supply current of 500nA (max)

■ 2.7 to 5.5V operating voltage

■ 2.5 to 5.5V oscillator operating voltage

■ Battery low Flag

■ Automatic switch-over and deselect circuitry

■ 44 bytes of general purpose RAM

■ Programmable Alarm and interrupt function (valid even during battery back-up mode)

■ Accurate programmable Watchdog timer (from 62.5ms to 128s)

■ Microprocessor power-on reset

■ Choice of power-fail deselect voltages (VCC = 2.7 to 5.5V):

– THS = VSS; 2.55V ≤VPFD ≤2.70V

– THS = VCC; 4.20V ≤VPFD ≤4.50V

■ Packaging includes a 28-lead SOIC and SNAPHAT? TOP (to be ordered separately) or 16-lead SOIC

■ 28-lead SOIC package provides direct connection for a SNAPHAT TOP which contains the battery and crystal