# Crystal SMD 3215

The 3215 (3.2 x 1.5mm) is one of the most popular SMD crystal packages. Available in frequencies from 32.768kHz (real-time clock) to tens of MHz (MCU main oscillator), it provides the timing reference for virtually all digital electronics. The 32.768kHz variant (2^15 Hz) divides cleanly to 1-second intervals for RTCs in every microcontroller. MHz variants serve as main clock sources for STM32, ESP32, and RP2040 designs. The compact 2-pin ceramic package mounts close to the MCU for short trace lengths and minimal parasitic capacitance.