ST's serial real-time clocks range from ultra-low power devices for portable applications to high-accuracy parts with analog calibration up to factory-calibrated RTC modules with an embedded crystal.
SRAM supervisor functions can transform a standard volatile SRAM into a non-volatile type of memory by using the backup power of the RTC. Additional functions like programmable watchdog, an early power-fail warning circuit and the power-on reset/low-voltage detect feature provide support for master MCU operations. The programmable alarm with repeat mode may be used for battery back-up operations.
Battery with crystal option
ST's removable/replaceable SNAPHAT® battery top contains a lithium coin-cell battery and a 32-kHz crystal. It is compatible with all of ST's serial- and parallel-interface real-time clocks in surface-mount SOH-28 and SOH-44 packages.
The SNAPHAT top is designed to be "snapped on" after the SOIC is surface-mounted on the PC board, preventing the battery and crystal from being exposed to the high temperatures of the surface mount process.