IMXRT1064 Power Up sequence

[alberto2]

Hi,

the document "Hardware Development Guide for the MIMXRT1050/MIMXRT1060 Processor" clearly recommends respecting the power-up sequence showed in figure 1 of the document.

This would require the introduction of a DC/DC converter that is enabled through the PMIC_ON_REQ pin of the IMXRT1064 once the VDD_SNVS_IN is turned on (figure 2 of HW development guide).

However, on the IMXRT1064 datasheet, in section 4.2.1.1 Power-up sequence we can read: "VDD_SNVS_IN supply must be turned on before any other power supply or be connected (shorted) with VDD_HIGH_IN supply."

To my eyes, this is contradictory since if VDD_SNVS_IN is shorted to VDD_HIGH_IN, the power-up sequence showed in figure 1 of the hw development guide is not respected, since all the voltage references are being turned on at the same time.

Can you please clarify this?

Is it ok to short VDD_SNVS and VDD_HIGH_IN, or we need a sequencing element (DCDC or load switch enabled from pmic_on_req)?

Thank you.

Alberto

[victorjimenez · Accepted solution]

Hello Alberto, 

Can you please clarify this?

The statement "VDD_SNVS_IN supply must be turned on before any other power supply" applies only when you have a backup battery. If your application doesn't need a backup battery then you need to short VDD_SNVS_IN with VDD_HIGH_IN and in this case, the previous statement doesn't apply. 

Is it ok to short VDD_SNVS and VDD_HIGH_IN, or we need a sequencing element (DCDC or load switch enabled from pmic_on_req)?

It's ok if you short VDD_SNVS_IN and VDD_HIGH_IN, you don't need any extra circuitry. 

Have a great day,
Victor

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