Kinetis Microcontrollers中的主题 Re: Should I use an external resistor to pull up the boot pin?

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

laszlomonda — Mon, 17 Apr 2017 22:47:49 GMT

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

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

kerryzhou — Wed, 19 Apr 2017 01:40:27 GMT

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

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

laszlomonda — Thu, 27 Apr 2017 00:32:33 GMT

Got it! Thank you, Kerry!