What is this SMT component with a little window, labeled A247L? (solved!)

5 comments

Okay, I think this is a passive crystal from Seiko-Epson. I've never seen one in this package.

Edit: https://www5.epsondevice.com/en/products/crystal_unit/fc135r.html
- Yup looking at the components around and the layout, it does look like a quartz crystal, especially considering it's right next to the microcontroller, and the 2 beige components above are the matching capacitors.
  
  But yeah I've never seen a package with an open window. Maybe it's an ultra high precision that has been tuned with lasers (usually done for patch antennas).
  
  Who would need an ultra high precision quarz on an STM32 processor?
Interesting package, maybe @DavideAndrea@discuss.tchns.de knows more about it?

Edit, the tag somehow didn't work: https://discuss.tchncs.de/u/DavideAndrea