Can the odroid hc4 be powered with 12V ATX power supply rain?

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mnxford
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Can the odroid hc4 be powered with 12V ATX power supply rain?

Post by mnxford »

Hello,

Will the odroid-hc4 work perfectly fine from 12V rail of an ATX power supply when it has two Ironwolf 125 SATA NAS SSD attached to it? Can @odroid provide some technical specifications and configurations related to the power convertor that is present on the hc4 board for the barrel power conversion?

Thank You.

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Re: Can the odroid hc4 be powered with 12V ATX power supply rain?

Post by mctom »

Howdy,

Check out the HC4 schematics available on Odroid Wiki: https://wiki.odroid.com/lib/exe/fetch.p ... 200807.pdf

Take a look at U21 and U24 - there are two Buck converters providing 12V for each HDD.

These Buck converters can of course output only voltage lower than their input (coming from DC jack).
In some cases Buck converters may work on 100% PWM thus passing input voltage directly to the output, but this is not the one. PWM must be less than 100% to operate the very MOSFET that lets current pass from input to output.

According to datasheet, min. off time is 100ns with typical cycle time of 2us. That means if you're lucky this thing might output some 95% of input voltage, which would be 11.4V.

ATX standard mandates 5% tolerance on 12V rail, so HDDs are expected to work with 11.4V input instead of 12V, however this is a border case assuming all other factors are perfect.

Two thing that you can do is either *somehow* power your HC4 off >13V source, or bypass U21 and U24 entirely, by removing them and placing wires directly from DC_JACK node to P12V_n nodes. You may also remove L10 and L11 instead of U21 and U24.
This will cause your computer to lose control over these two power sources, ans they will act as always on. I'm not sure what this will lead to, but probably HDDs will remain always powered on.
And of course, in this case you'd have to stick to 12V input forever.

Disclaimer: I don't claim this is going to work :lol:
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Re: Can the odroid hc4 be powered with 12V ATX power supply rain?

Post by mnxford »

Thanks for the explained info @mctom

Your insight on this is really helpful. I was thinking about, what if I power the two SSD using ATX power supply directly using SATA power cables and only power the HC4 using 12V from the same ATX supply. If I do that the buck regulations will fall below the desired voltage but downstream will it affect the power needed by the HC4 itself? I will check the schematics in more detail to see what the downstream voltages look like going to power HC4 itself.

With the approach above I will not need to mod the HC4 board itself and tap into the power lines. What do you think?

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Re: Can the odroid hc4 be powered with 12V ATX power supply rain?

Post by mctom »

I think this should work. The internal 12V rails in HC4 will have incorrect levels, but that shouldn't matter as only HDDs use 12V.
All the remaining circuits in HC4 need 5V or less, so should work fine with 12V input.

The risks are the following:
- With lower input voltage HC4 will draw more current (to preserve more or less constant power). That may premature trip fuses (if any) or overload some circuits otherwise. I don't think this is a serious threat, just being smartass.
- If there is any sort of "housekeeping" that controls internal voltages, it may fail.
- If the DC jack has a global undervoltage protection, this will not work either.
- HC4 will lose control over 12V and 5V rails reaching HDDs, so software based shutdown or reset may be impossible. Shouldn't matter with SSDs though.

I'll let you study schematics on your own to see if any of the above applies to your case.
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Re: Can the odroid hc4 be powered with 12V ATX power supply rain?

Post by mctom »

Okay I couldn't resist taking a look into the schematic myself, so here's what I deduced:

- U13 is enabled with input voltage divided by 6.6 factor. "EN Rising Threshold" is specified at 1.5V minimum, but no maximum value is specified. Thus U13 (which provides a key 3.3V system voltage) theoretically should turn on with input voltage no lower than about 10V.
However when it turns on, it should stay on reliably, thanks to deep hysteresis of EN pin.
Will it turn on reliably at 12V? Only one way to find out, but I'm optimistic.

- I can't see any internal housekeeping components, but even if there were, 12V rail with no load should reach 12V even with PWM below 100%.

- No current limiters or fuses in sight.

It is also worth noting SY8120 converters are typically more efficient with lower input voltages, so you may actually save some power.
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Re: Can the odroid hc4 be powered with 12V ATX power supply rain?

Post by mnxford »

Thanks a lot for your insight on this @mctom So, basically a direct 12V connection to the barrel power connector should work without any modding I suppose. I will put some measurement probes on the input and output rails of the buck and check for overall system power stability while using 12V. I might also follow the schematics and do some testing on the SATA power and put up my findings in this forum post when I am done with it. Anyway, really appreciate the help.

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