[MinnowBoard] Minnowboard Max - power from USB port (questions)

[Anders, David]

Greetings All,

Reverse powering from the hub to the minnowboard max will not damage the board. the onboard TPS2066DR, which is the usb overcurrent and power protection, is intended to provide reverse power protection but for some reason does not. This part was replaced on the minnowboard turbot with the AP2172, which to the best of our knowledge has resolved the issue.

Dave Anders


From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of Douglas Kryder
Sent: Monday, June 13, 2016 10:11 PM
To: MinnowBoard Development and Community Discussion <elinux-minnowboard at lists.elinux.org>
Subject: Re: [MinnowBoard] Minnowboard Max - power from USB port (questions)

i read this also, today. at least one downside would be the voltage of the hub being greater than 5v. my hub, for instance, is powered by 12v power supply and i'm not certain how that is cobtrolled by the hub. however, i do not get the power leds staying lit up as you mentioned, so hopefully i'm ok. i just have a hard time thinking that the design of the hub would allow leakage out into the usb connector but i have fingers crossed anyway.

On Mon, Jun 13, 2016 at 4:38 PM, Chris Brookes <chris at txrx.org<mailto:chris at txrx.org>> wrote:
I saw the wiki entry on how a powered USB device might wind up pushing juice in to the Minnowboard Max due to the lack of a diode in the design. I have seen this happen myself and the Minnowboard, at least for the few  minutes I had it in this state, did not appear to suffer and did seem to work properly. Interestingly, in this state with power from 2 sources, if I unplugged either it would continue to operate as if nothing odd had happened. It was sort of like having dual independent PSU’s.

What is the risk in leaving it in this state? It’s obviously out of spec, not a good idea generally and so on, but what could happen, what probably would happen, and what (if anything?) definitely will happen if it’s left to operate in this state for any period of time?

Just curious…

Chris

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