Should I use an external resistor to pull up the boot pin?

[laszlomonda]

Hi guys,

I use the KL03 and I'll unset the BOOTPIN_OPT flag of the FTFA_FOPT register. I'd like to make the user able to short GND and the boot pin during reset to trigger the bootloader as a safety firmware upgrade method.

My question is whether I need to use a pull-up resistor for the boot pin, or is the internal pull-up sufficient.

Thanks in advance!

- Laci

[kerryzhou · Accepted solution]

Hi Laci,

   Please take care, the BOOTCFG0 pin is also the /NMI pin, from the /NMI pin recommend design, it is better to add the external 4.7K to 10K pull up resistor.

   http://cache.nxp.com/assets/documents/data/en/user-guides/KLQRUG.pdf?fsrch=1&sr=1&pageNum=1 

Page 23, chapter 2.1.3.4.1 RESET_b and NMI_b.

   The MCU can work if you don't add the external pull up, but for good design, I suggest you to add the external 4.7k to 10K pull up resistor.

Wish it helps you!

Have a great day,
Kerry

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[laszlomonda]

Got it! Thank you, Kerry!