IMXRT1176 power up sequence

[Ajas]

Hi,

My application uses RT1176 without battery & sleep mode, like Eugene3 as mentioned in a previous post.

I would like to know if you can help me to check the power on and power off sequences.

See attached the power control diagram.

(I already checked the file MIMXRT1170EVKHUG.pdf)

Thanks for your help.

[Ajas]

Hello Diego,

1) If we do not use ONOFF, do we need to handle the PMIC_ON_REQ ? Can we ignore PMIC_ON_REQ signal?

2) What is the main difference between POR pin and power on reset ?

Thanks

[diego_charles]

Hi @Ajas 

I hope that you are doing great. 

I can not see the power sequence and power off sequences you mention. However,  you need to ensure that they meet our specification, as shown  RT1170 DS ( IMXRT1170IEC ) section 4.2.1 Power supplies requirements and restrictions. Feel free to let me know if you have any specific questions!

Is this desing under test at this moment? I have checked your power control diagram and it seems to be okay, but I can not guarantee. 

Best regards, 

Diego

[Ajas]

Hello @Diego,

1) If we do not use ONOFF, do we need to handle the PMIC_ON_REQ ? Can we ignore PMIC_ON_REQ signal?

2) What is the main difference between POR pin and power on reset ?

Thanks

[diego_charles]

Hi @Ajas 

Many thanks for your patience. 

Regarding your questions. 

1 If you do not use ONOFF, the  Chips FSM ( finite state machine  ) of the SRC ( system reset controlled) will only set  PMIC_ON_REQ to 1 and that's it.

If you design does NOT use PMIC_ON_REQ signal  for turning on any external PMIC or external circuitry you can ignore it and leave it unconnected, as well for the PMIC_STBY_REQ signal. 

See below figures from the RM,  where PMIC_ON_REQ can be used or not used depending on the application. 

Please note that despite Figure 25-2 does not show a use for the PMIC_ON_REQ, this output signal is still controlled by the ONOFF input pin.  As show in the below snapshot.

In summary , If you do not connect the ONOFF, it is expected that PMIC_ON_REQ is set to 1, after POR. 

By the way,  you can leave ONOFF unconnected or with a termination resistor to pull it up.

2 The POR pin (POR_B pin  or SRC_POR_B pin ) is simply an input of the SRC, that when it is held low it triggers the POR sequence of the chip, and also must be held during the complete power on sequence. The POR comprehends whole power on reset sequence of the chip. 

I hope this could help, if you have further questions, do not hestitate to let me know! 

Best regards, 

Diego.