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SNVS_PMIC_ON (AB8) seemingly being driven high when RTC battery is attached.

Question asked by Evan Edstrom on Mar 7, 2018
Latest reply on Mar 8, 2018 by Evan Edstrom

I am working on a board using the i.MX7D and PF3000 PMIC. The SNVS_PMIC_ON signal from the i.MX is driving the PMIC's PWRON pad. When powered off this should be LOW. And that is true if I run the poweroff command from linux, or by setting the "TOP" bit of the SNVS_LP register.

 

However when the RTC battery (powers VDD_SNVS_IN) is first inserted  or when power is removed abruptly (power cord is pulled out), the SNVS_PMIC_ON signal from the i.MX is HIGH (about 2.5v) which is apparently enough to turn on the PMIC enough to draw too much current from the battery. It's not a lot, but it matters for this application.

 

How can I get the SNVS_PMIC_ON to go and stay low when power is removed from the board? Is there a SNVS register I'm missing or something?

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