I.MX RT1024 POR_B pin is not used

[Rajender]

Hi,

I am designing a custom board using i.mx RT1024 MCU.

In the EVK the POR_B signal is driven with a reset supervisor IC but in our schematic we would like to not use external POR as internal POR does the same function.

Are there any other issues i may face if i don't external POR? or is it normal to not use external POR?

[jeremyzhou · Accepted solution]

Hi,
Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
1) Are there any other issues i may face if i don't external POR? or is it normal to not use external POR?
-- -To be prudent, I'd like to know the exact meaning of not using the external POR.
Have a great day,
TIC

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[Rajender]

Hi jeremy,

Thanks for your quick reply!

By mentioning external POR, i was referring to POR_B pin of the MCU which is AND'ed with internal POR of MCU. It is mentioned that if POR_B is not used then it can be unconnected or pull high but i want to know will there by any other issues during bootup/power up if POR_B left unconnected.

Regards,

Rajender

[jeremyzhou]

Hi，
Thanks for your reply.
There are some issues that may arise, such as boot-up instability, can't use boot_mode pins to configure the boot mode, etc.
Have a great day,
TIC

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[Rajender]

Hi Jeremy,

I didn't get it! Can you please elaborate more on it? or can you please share any documentation related to it?

This is how i unconnected POR_B in the schematic.

Regards,

Rajender.

[jeremyzhou]

Hi，
Thanks for your reply.
1) Can you please elaborate more on it? or can you please share any documentation related to it?
-- As the Hardware Development Guide for the
MIMXRT1050/MIMXRT1060 Processor, the i.MX RT needs to follow the sequence of the below power-up, further, the BOOT_MODE register is initialized by sampling the BOOT_MODE0 and
BOOT_MODE 1 inputs on the rising edge of the POR_B, to make sure the system boot with stability, it's usually recommended to use an external reset IC to connect the POR_B in the design actually.
Have a great day,
TIC

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