m41t56c64 STMicroelectronics, m41t56c64 Datasheet - Page 5

• Manufacturer Part Number: m41t56c64
• Description: Serial Real Time Clock With 56 Bytes Of Nvram+64 Kbit 8192 Bit X 8 Eeprom
• Manufacturer: STMicroelectronics

M41T56C64
1
1.1
Summary description
The M41T56C64 is a low power, Serial Real Time Clock with 56 bytes of NVRAM plus a
64Kb EEPROM (see
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 M41T56C64 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 RAM and clock operations can be supplied from a small lithium coin cell.
Typical data retention time for the Serial RTC is in excess of 10 years with a 50mAh, 3V
lithium cell. The M41T56C64 is supplied in an 18-lead Plastic SOIC package.
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
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.
1. Open drain output
Figure
Logic diagram
4). This calibration value will be written into address 1550h of
Figure
SCL
3). A built-in 32,768Hz oscillator (crystal controlled) and the first
WC
E
E
E
0
1
2
V
(EEPROM)
V
CC
M24C64
M41T56
SS
+
V
BAT
SDA
FT/OUT (1)
AI09123
Summary description
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