topic Re: about I.MX8 Plus_ONOFF_RTC pin in i.MX Processors

about I.MX8 Plus_ONOFF_RTC pin

mark_kim — Wed, 28 Apr 2021 11:27:55 GMT

Dear

Could you confirm if there is any problem when user remove ONOFF Switch and RTC ?

Due to certain reason, We need to apply belwo concept to ONOFF and RTC.

- Not use external RTC 32.768KHz

- Short ON/OFF to GND permanently.

Q1) Could you let me know what hapen when not use external RTC 32.768KHz?

Q2) Regarding ON/FF pin, I can see " A brief connection to GND in OFF mode causes the internal power management state machine to change state to ON " from I.MX 8 M Pluse Hardware Developer's Guide.

So. I guess Even when ONOFF pin is shorted to GND without ONOFF Button used on referenceboard while board is operated, It doesn't affect I.MX8.

Please let me know if this idea is a proper way.

thank you for your consideration

Best Regards

Mark Kim

Re: about I.MX8 Plus_ONOFF_RTC pin

igorpadykov — Thu, 29 Apr 2021 00:26:44 GMT

Hi Mark

- 32.768KHz clock is mandatory as explained in Table 11. Oscillator/Crystal recommendations
i.MX 8M Plus Hardware Developer’s Guide

- ON/OFF pin can not be shorted to GND, from Table 7. Reset and ON/OFF recommendations
:
"The connection to GND for approximate 5 seconds or more causes a forced OFF."

Best regards

igor

Re: about I.MX8 Plus_ONOFF_RTC pin

mark_kim — Sun, 02 May 2021 10:31:47 GMT

Dear Igor

appreciate your anwwer. but I need your more help.

Question) whenever I read Tab7. Reset and ON/OFF Recommenation, I can’t clearly catch up with recommendation for ONOFF pin.

From the Recommendation column, We can assum that ONOFF pin can be connected to GND.

Table 7 Says on Recommendation column that For portable applications, the ONOFF pin may be connected to an ON/OFF SPST push-button switch to ground.

An external pull-up resistor is required on this pin

But From Explanation/supplemental recommendations, Table 7 says as below

A brief connection to GND in OFF mode causes the internal power management state machine to change state to ON.

In ON mode, a brief connection to GND generates an interrupt (intended to initiate a software-controllable power down).

The connection to GND for approximate 5 seconds or more causes a forced OFF.

Taking Second recommenation into cosideration , It is impossilbe to connect ONOFF pin to GND via SPST for portable application.

But when I see first recommendation, NXP recommends to be able to connect ONOFF pin to GND via SPST in Device and application operation

Only consiering first recommendationm, It should not affect board operation even when ONOFF pin is connected to GND for more than 5 seconds

Please clarify ONOFF Handling. A board has limited space. So it is hard to add additional componet like Switch /Button.

Is it recommendable to add RC time constant circuit to ONOFF pin for stable Power sequcne?

To explain simply, I want to construct a circuit that works right away as soon as the power is applied without Button/Switch for ON/OFF

thank you

Best Regards

Mark Kim

Re: about I.MX8 Plus_ONOFF_RTC pin

mark_kim — Thu, 06 May 2021 13:56:39 GMT

Dear Igor

Could you let me have your answer for this ticket?

thank you

Best Regards

Mark Kim

Re: about I.MX8 Plus_ONOFF_RTC pin

igorpadykov — Fri, 07 May 2021 00:37:51 GMT

Hi Mark

ON/OFF pin can not be shorted to GND.

Best regards

igor

Re: about I.MX8 Plus_ONOFF_RTC pin

mark_kim — Wed, 12 May 2021 22:41:13 GMT

Hi Igor

I am sorry to interrupt you again. But Customer wants to get a circuit Vendor recommends.

As I wrote before, Customer wants to construct a circuit that works right away as soon as the power is applied without Button/Switch for ON/OFF"

So I recommended to add supervisor IC or RC constant circuit but He strongly wants to get Vendor recommendation

thank you

Best Regards

Mark Kim

Re: about I.MX8 Plus_ONOFF_RTC pin

mark_kim — Fri, 21 May 2021 05:12:53 GMT

Dear

I look forwared to a feedback?

thank you

Best Regards

Mark Kim

Re: about I.MX8 Plus_ONOFF_RTC pin

igorpadykov — Fri, 21 May 2021 10:49:44 GMT

Hi Mark

recommendation is to follow nxp supporting information and reference design

https://www.nxp.com/design/development-boards/i-mx-evaluation-and-development-boards/evaluation-kit-for-the-i-mx-8m-plus-applications-processor:8MPLUSLPD4-EVK

Other recommendations are not available, sorry. Custom specific requirements may be supported

with NXP Professional Services: https://contact.nxp.com/new-prof-svcs-sw-tech

Best regards
igor