По теме, на почту, в рассылке от All About Circuits, пришло:
"SiTime claims it has developed the industry’s smallest and lowest
power 32.768 kHz crystal oscillator (XO) to address the timing
requirements of ever-shrinking mobile products. At 1.2 mm x 1.1 mm
x 0.55 mm, the SiT1811 is 30% smaller than competing oscillators." "Further, it breaks ground in power reduction with a 510 nA current draw (typically < 0.6 µW). The SiT1811 operates at 32.768 kHz with an integrated phase jitter (IPJ) of 3 ns RMS. The XO is accurate to ±20 ppm (about 1.7 seconds per day). SiTime says the XO is well suited to low-power devices with an operating voltage range of 1.35 V to 1.98 V."
Особенно, меня впечатлила стойкость к ускорениям и среднее время наработки на отказ: "The oscillator is a robust device with a mean time between failures (MTBF) of more than two billion hours (228,310 years). As a mobile-targeted component, the SiT1811 features a mechanical shock resistance of 20,000 g and vibration resistance of 100 g—both best-in-class specifications.
https://www.allaboutcircuits.com/news/sitime-introduces-smallest-and-lowest-power-32khz-crystal-oscillator/