FC3215AN32.768K-70NN50KC3 is a low-ESR 32.768 kHz crystal unit designed for sub-clock applications in battery-powered IoT devices, wearable products, and low-power microcontrollers. The device features a compact 3.2 × 1.5 mm package with a maximum thickness of 0.9 mm, combined with a robust Pb-free metal lid and seam-sealed construction. It delivers typical ESR of 35 kO at +25°C, with maximum ESR of 50 kO across the -40°C to +85°C range and 60 kO at -40°C to +105°C, ensuring stable performance across extended temperature ranges. The crystal exhibits a frequency tolerance of ±20 × 10?6 at +25°C ± 5°C and supports frequency aging of ±3 × 10?6 in the first year. This device is ideal for applications requiring minimal current consumption and reliable timekeeping in harsh thermal environments, with RoHS compliance and Moisture Sensitivity Level 1 rating.