A Versatile Timing Microsystem Based on Wafer-Level Packaged XTAL/BAW Resonators With Sub-$\mu$ W RTC Mode and Programmable HF Clocks

This paper introduces and demonstrates with high yield a novel concept for the packaging under vacuum of tuning fork quartz XTALs on top of a silicon interposer equipped with TSVs. It paves the way to the implementation of a monolithic timing microsystem where the ASIC is part of the housing of a newly designed tiny 131-kHz XTAL to reach extreme module miniaturization (1.5
$\,\times\,$
1.1
$\,\times\,$
0.7 mm
$^{3}$
) and integrity. As this task is still ongoing, an early demonstration of the generic versatile timing module is presented using a chip-on-board approach with standalone conventionally packaged XTAL and BAW resonators. The module achieves 0.4
$\mu$
W power dissipation and
${\pm} $
2 ppm stability over
${-}$
40
$^{\circ}$
C to 85
$^{\circ}$
C in RTC mode and can deliver on-demand programmable clocks between 1–50 MHz. The latter are obtained either with a RC PLL or after division of the signal obtained from a 2-GHz BAW DCO at a power dissipation of 100
$\mu$
W and 5.3 mW, respectively.