Real-Time Clock Chip with EEPROM and Embedded Crystal from STMicroelectronics

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 EEPROM-RTC-crystal combination is built with ST’s proven stacked die packaging technology, which enables the integration levels of hybrid technology for only a slight additional cost over monolithic packaging. Allowing users to significantly reduce board space, the M41T56C64 is rated for 4.5 to 5.5 volts and operates over the industrial temperature range,–40° C to +85°C.