Supply IMX6UL via PM3000

[semirfazlagic]

Dear Sir./Madam

We are in phase of developing our board based at IMX6UL +PM3000.

I read all available documents  and also some discussion at forum and I have yet some doubts about pins VDD_HIGH_IN and VDD_SNVS_IN.  Reading data sheet  of IMX6UL seems that these two domains are full independent, but

analyzing development guide IMX6ULHD6 (page 12) and thread: PF3000 PMIC questions, Dec. 2015 

I understand that anyway there is some interaction between these two domains inside IMX6UL.

.

Unfortunately in official data sheet there is no any info about it and I have now some doubt

My system will not use any coin  and following your suggestion in thread (presented above) I decided to use in this way:

1) VSNVS output from PM3000 (pin 34) = 3V connect to VDD_SNVS_IN od IMX6UL via diode schotky

2) VDD_HIGH_IN will be connected  to fixed 3.3 (some regulator)

My question: Is this good approach and can I be sure (see page 12 of IMX6ULHD6) that VDD_SNVS_N domain of IMX6UL

will be supplied with 3V3 coming from VDD_HIGH_IN ? I understand in this way comments at page12 of IMX6ULHD6.

It is important for me, because I will use Tampers as GPIO and also other special signals supplied from VDD_SNVS_IN domain and I want to be sure that I/O levels will be 3V3 (not 3.0-0.3 = 2.7, if supplied from VDD_SNVS_IN pin)

I hope that my question is clear.

Thank in advance

Best regards

.

[reyes]

Hello,

VSVNS from the PF3000 is 3.0V, and you have 3.3V on the VDD_HIGH_IN rail, so, VDD_HIGH_IN > VDD_SNVS_IN, and VDD_HIGH_IN supplies all SNVS domain current and current flows into VDD_SNVS_IN even if there is no coin cell battery to charge, therefore, it is recommended to have the schotky diode connected from VDD_HIGH_IN rail to VDD_SNVS_IN rail as can be seen in the image below:

Have a great day,
Jose

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[semirfazlagic]

Hi Ross and Jose
Thank you for your very professional answers and support>
It is right what I needed

Regards

[RossMcLuckie]

Hi,

You may want to look here for a good reference -

PMIC PF3000/3001 + i.MX 6UL Resources  

There is indeed a link between the VDD_HIGH and VDD_SNVS domains, the Hardware Development guide details some of this -

http://www.nxp.com/assets/documents/data/en/user-guides/IMX6ULHDG.pdf 

Chapter 10 and 37 of the Reference Manual provide more detail, for example -

In your specific case, where no back-up battery is in use, the recommendation would be to power both HIGH and SNVS from the same supply, this simplifies things greatly and makes it less likely you will see any issues.

Regards

Ross