IMX6Q and PF0100A SNVS_IN/HIGH_IN

[leonardoprates]

At my custom board I connected PF0100 source VSNVS (pin 43) to VDD_SNVS_IN of IMX6Q and VSW4 of PF0100 (3.15V) at VDD_HIGH_IN. I don't use coin cell connected to LICELL pin of PF0100. HW development guide states:

"When VDD_HIGH_IN > VDD_SNVS_IN, VDD_HIGH_IN supplies all SNVS domain current and current flows into VDD_SNVS_IN to charge a coin cell battery"

In this situation, how PF0100 deals with reverse current flow? Do I have to put a block diode or PF0100 already have one internally? PF0100 datasheet just suggest direct connection between VSNVS and VDD_SNVS_IN without any warning. Could this connection burn PF0100 / IMX6 or current involved are too low?

The HW development guide states too: "The i.MX6 must have a VDD_HIGH voltage greater than approximately 2.4V to enable the VDD_HIGH to SNVS charging path. This instantaneous current flow from VDD_SNVS_IN can cause damage to the i.MX6. The current limiting series resistor should be sized to match the charging current limits of the battery".

Is this warning true only if I connect the battery directly to VDD_SNVS_IN? Because using PF0100 the coin cell is connected at a specific pin at PMIC, without direct path to the battery. At my case any battery is connected at all.

Could a expert help me?

Thanks, Leonardo

[Yuri]

@leonardoprates 
Hello,

    Customers can follow i.MX6 reference design(s). In particular - A schottky diode is required between VDD_HIGH_IN and VDD_SNVS_IN in order  to limit the voltage difference between the two power domains to approximately 0.3 V. 

Regards,
Yuri.

[leonardoprates]

I haven't to worry about reverse current path between this diode to the SNVS output of PF0100 right?

[Yuri]

@leonardoprates 
Hello,

  Yes, do not worry about reverse current path between this diode to the SNVS output of PF0100.

Regards,
Yuri.

[fabiopavanati]

Yuri,

Leonardo has made some questions that are relevant to my case, that wasn't answered. I'm developing a SoM with the iMX6 with the PF0100 PMIC. The coin cell is connected to the PMIC's LICELL pin, and the PMIC's SNVS output pin is connected directly to iMX6's VDD_SNVS_IN pin.

The HW development guide states too: "The i.MX6 must have a VDD_HIGH voltage greater than approximately 2.4V to enable the VDD_HIGH to SNVS charging path. This instantaneous current flow from VDD_SNVS_IN can cause damage to the i.MX6. The current limiting series resistor should be sized to match the charging current limits of the battery".

I understand that iMX6 could be damaged by the instantaneous current flow. So, shouldn't the resistor be sized so that the current does not exceed the current limits of the iMX6? What is this current?

Best regards,

Fabio