ECS Inc.'s most cost-effective compact 32.768 kHz tuning fork crystal on the market. 

The ECX-31B comes in a 3.20 mm x 1.50 mm x 0.90 mm industry standard package that offers an ESR of 70 kΩ. The 32.768 kHz tuning fork offers a standard ±20 ppm tolerance with a ±10 ppm option available, and all components offer an industrial operating temperature range of -40ºC to +85ºC. This surface mount tuning fork offers load capacitance options of 6pF, 7pF, 9pF and 12.5pF. The ECX-31B is offered in two reel sizes: the -TR is a 3,00-piece reel and the -TR9 is a 9,000-piece reel. This component is ideal for mobile, industrial, wireless and low power RTC applications. It is also recommended for the STM32 via the AN2867. 

For more information on ECS Inc. recommended timing solutions for STM32 microcontrollers, use our STM32 crystal selection tool here.