M41T00SC64

Summary description

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Summary description

The M41T00SC64 is a low power, Serial Real Time Clock plus a 64Kb EEPROM (see

Figure 3). A built-in 32,768Hz oscillator (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 M41T00SC64 clock has a built-in power sense circuit which detects power failures and

automatically switches to the battery supply during power failures. The energy needed to

sustain the clock operations can be supplied from a small lithium coin cell.

Typical data retention time for the Serial RTC is in excess of 9.5 years with a 50mAh, 3V

lithium cell. The M41T00SC64 is supplied in an 18-lead Plastic SOIC package.

1.1

Calibration

As the crystal is molded together with the silicon in this package, ST can program the

appropriate calibration value necessary to achieve ±5 ppm accuracy at 25°C after two SMT

reflows (see Figure 4). This calibration value will be written into address 1550h of

the EEPROM. This clock accuracy can then be guaranteed to drift no more than ±3 ppm the

first year, and ±1 ppm for each following year due to crystal aging.

Figure 1.

Logic diagram

1.

Open drain output

AI09123

M41T00S

+

M24C64

(EEPROM)

SCL

WC

SDA

FT/OUT

(1)