The M4Txx-BR12SH SNAPHAT®top is a detachable lithium power source for ST’s serial real-time clock and non-volatile TIMEKEEPER®surface-mount SOIC package (28- and 44-pin). The SNAPHAT top contains both the battery and crystal and 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.