New Real-Time Clock Chip with EEPROM and Crystal From ST

Minimizes space requirements and eliminates need for external crystal

STMicroelectronics has announced a high accuracy Serial Real-Time Clock (RTC) which adds EEPROM and an embedded crystal in a single, space-saving 18-pin SOIC (Small-Outline Integrated Circuit). ST's new M41T56C64, reduces board space, increases reliability, and lowers manufacturing costs, making it an ideal choice for applications requiring accurate timekeeping and non-volatile data storage. Among these applications are metering devices, medical equipment, vending machines, and Point of sale (POS) terminals.

The Real-Time Clock (RTC) section of the device provides year, month and day data along with hours, minutes, and seconds. Drawing only 450nA (typical), the IC can accurately keep time for more than ten years on a 48mAh lithium coin cell. The EEPROM section has 8192 bytes of memory with more than 1 million erase/write cycles per byte.

The RTC and the EEPROM are accessed via a two-wire I²C (Inter-Integrated Circuit) serial bus. The M41T56C64 also embeds the pre-calibrated 32-kHz crystal, with ±5ppm accuracy guaranteed even after two reflows. Embedding the crystal also provides better protection against the corrosive effects of moisture and humidity while avoiding manual insertion during board assembly.

The M41T56C64 includes 8 bytes of BCD (binary-coded decimal) registers used for the clock/calendar functions, 56 bytes of NVRAM and 8Kbytes of EEPROM. When power is removed, the device automatically switches to its backup battery input and goes into a low-current mode to maximize battery life.

The STMicroelectronics website address is www.st.com
[Reprinted with kind permission from STMicroelectronics]