[BPI-R4] (Yet another) Question regarding DC

Hi forum. I’m going to power R4 from Lead–acid battery for a while. It have outputs somewhere in range 11.6 ~ 14.9V. I’m going to do that via DC port. The question is - is it safe to do that? From various threads I saw that internal DC/DC should be fine up to 24V, however it’s not very clear, is it’s about USB-C input or all 3 inputs are fine with those ranges. Also - is it safe to have input with undervoltage (<12V). While it’s clear, that system unlikely to be stable, I’m more interested in physical safety. I have feeling that this setup made my BPI-R2 broken/dead, so want to try to clarify this first…

Schematic says:

DCIN:8~24V

I tried to read the one from bpi docs here and can’t say understand a lot because of lack of knowledge. I believe the part about DC is at page 3, which is marked 12~24V. I tried to get datasheets of mentioned components, and I think it all ends with AON7934 and MT6682A which should work together as DC/DC. However I can’t find datasheet for MT6682A, and wondering, where you found that 8~24V range?

I looked into the internal datasheet for bpi-r4 v1.1,but maybe there is an error when public says 12-24

Found datasheet for RT5190 here

Schematic says pmic has 12V connected, so i guess the 8-24 is wrong there (i see no step-up)…so it should have at least 12V as input, but it seems to can be higher.

maybe @simon can answer it completely

All voltages used in the BPI-R4 internal circuits are below 5V, so PMIC and DC-DC Buck Converters are used to convert the input power into various required voltages.

The maximum voltage that the DC-DC and PMIC can withstand is 26V, but we have designed overvoltage protection, and the input can work normally as long as it does not exceed 24.1V

The “+12VD” on the schematic may not be very accurate, and the actual input voltage range can be 8~24.1V (But please note that many 24V power supplies will have a 5% tolerance, and the maximum voltage can reach 25.2V, at which time R4 will shut down)

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