SUMMARY DESCRIPTION
The M41T56 TIMEKEEPER® is a low power, 512-bit static CMOS RAM organized as 64 words by 8 bits. A built-in 32,768Hz oscillator (external crystal controlled) and the first 8 bytes of the RAM are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. Addresses and data are transferred serially via a two line, bi-directional bus. The built-in address register is incremented automatically after each WRITE or READ data byte.
The M41T56 clock has a built-in power sense circuit which detects power failures and automatical ly switches to the battery supply during power failures. The energy needed to sustain the RAM and clock operations can be supplied from a small lithium coin cell.
Typical data retention time is in excess of 10 years with a 50mAh, 3V lithium cell. The M41T56 is supplied in an 8-lead Plastic SOIC package or a 28-lead SNAPHAT® package.
The 28-pin, 330mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT housing contain ing the battery and crystal. The unique design allows the SNAPHAT battery package to be mounted on top of the SOIC package after the completion of the surface mount process. Insertion of the SNAPHAT housing after reflow prevents potential battery and crystal damage due to the high temperatures required for device surface mounting. The SNAPHAT housing is keyed to prevent reverse insertion. The SOIC and battery/crystal packages are shipped separately in plastic anti static tubes or in Tape & Reel form.

FEATURES SUMMARY
■ 5V ±10% SUPPLY VOLTAGE
■ COUNTERS FOR SECONDS, MINUTES, HOURS, DAY, DATE, MONTH, YEARS, AND CENTURY
■ YEAR 2000 COMPLIANT
■ SOFTWARE CLOCK CALIBRATION
■ AUTOMATIC POWER-FAIL DETECT AND SWITCH CIRCUITRY
■ I2C BUS COMPATIBLE
■ 56 BYTES OF GENERAL PURPOSE RAM
■ ULTRA-LOW BATTERY SUPPLY CURRENT OF 450nA
■ LOW OPERATING CURRENT OF 300µA
■ OPERATING TEMPERATURE OF –40 to 85°C
■ AUTOMATIC LEAP YEAR COMPENSATION
■ SPECIAL SOFTWARE PROGRAMMABLE OUTPUT
■ PACKAGING OPTIONS INCLUDE:
   – 28-lead SOIC and SNAPHAT® TOP (to be ordered separately)
   – SO8