A Versatile Timing Microsystem Based on Wafer-Level Packaged XTAL/BAW Resonators With Sub-µW RTC Mode and Programmable HF Clocks. - David Ruffieux; Nicola Scolari; Frédéric Giroud; Thanh-Chau Le; Silvio Dalla Piazza; Felix Staub; Kai Zoschke; Charles Alix Manier; Hermann Oppermann; Tommi Suni; James Dekker; Giorgio Allegato (IEEE J. Solid State Circuits, 2014)