What does the second IC do in the Teensy LC?

[MrIndeciso]

Hi,
I'm thinking of buying a Teensy LC for a personal project that's going to be soldered on a PCB, but obviously before I need to debug it on a breadboard.
So if I debug my project (a special fan controller) on a breadboard and then solder the components on a PCB, is the second and smaller chip needed? Because I can't find anything on it, and from the schematic it doesn't seem to be doing anything important.
Thank you

 

[manitou]

If you are referring to MKL02Z32VFG4, it's the bootloader chip. Don't leave home without it.
https://www.pjrc.com/store/ic_mkl02.html

 

[markb]

It's probably possible to do without it, if you want rework the bootloader code, but it wouldn't be a Teensy, anymore. And it would be much easier to brick with the bootloader on the main processor.

 

[GremlinWrangler]

The second IC is holds the bootloader. Classic Arduino has code in general flash space that manages the download on reboot, but if anything happens that writes to that flash space, or sets things up such that the code breaks (slow clock, deep sleep) then board is bricked. Teensys have the bootloader IC which when triggered takes over the main CPU and writes the bootloader to RAM and resets the configuration bits via the hardware programing port. So harder to brick and all flash is availible for user code at the cost of higher BOM.

So going back to your project if you want it to work as an Teensy LC you need that chip. If you want to prototype with an LC and then burn your file using a COTS programing pod (or a homebrew solution with the bootloader chip in some form) that works (and some commercial products around like this) but once in the wild you can't reprogram it without adding some form of bootloader into your code. Which may even be a feature depending on your application.