ST's serial real-time clock devices combine the RTC function with the supervisor function for different master devices such as microprocessors and NVRAMs.
The features related to supervising a microprocessor include a programmable watchdog, an early power-fail warning circuit and the power-on reset/low-voltage detect. To protect an NVRAM, they can generate an automatic battery switchover and a write-protect signal, a power-fail deselect voltage and the battery-low monitor flag. The programmable alarm with repeat mode may be used in the battery back-up mode.
Battery with Crystal Option
ST's removable/replaceable SNAPHAT® battery top contains a Lithium coin cell battery and a 32KHz crystal. It is compatible with all of ST's real-time clocks and TIMEKEEPER® devices in the 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. Thus the two piece solution prevents the battery and crystal from being exposed to the high temperatures of the surface mount process.
To evaluate the battery capacity consumption and lifetime: Real-time clocks and TIMEKEEPERs battery life calculation
Real-time clock for demanding wearable devices
ST’s M41T62LC6F real-time clock is the perfect match for wearable devices when size, weight, and power-efficiency matters.
It offers a very low frequency error at 25 °C which equates to about 5 seconds per month, an ultra-low power consumption of 350 nA in standby, and comes in an ultra-small 1.5 x 3.2 mm package with an embedded crystal oscillator.