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