5V or 12V

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Cyrille
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5V or 12V

Post by Cyrille »

Hi,

As a previous C2 user, I was wondering if there’s a hardware explanation for the 12V/2A use instead of the 5V/2A power supply ? I checked the Odroid C4 Schematics and the DC/DC converters input votage range include 4.5V to 17 or 18V.
I can already tell you that the target application for which I’m using the Odroid C4 does not need more than 10W power consumption and that I’m only using :
- The HDMI Interface
- The Network Interface
- The EMMC Interface
So I’m not using any USB interfaces.
I’ve read also on technical specifications that DC jack input voltage range is between 5.5V and 13V. Could you give me any hardware reason why 5.5V and not 5V or 4.5V (as described in the C4 schematics)?

Thank you very much !

Cyrille

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Re: 5V or 12V

Post by crashoverride »

Cyrille wrote:
Thu Sep 23, 2021 5:36 pm
I was wondering if there’s a hardware explanation for the 12V/2A use instead of the 5V/2A power supply ?
It is likely due to the change from USB2 to USB3. USB2 ports are required to provide 500ma per port while USB3 ports are required to provide 900ma per port.

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Re: 5V or 12V

Post by Cyrille »

Yes, it's probably one of the reason why we need more power but it doesn't answer my questions which are :
- Why 12V DC IN whereas we regulate the output voltage to 5V, 3.3V and 1.8V (which are the usable voltage values for the C4) ?
- Why specify an input voltage range from 5.5V to 13V whereas according to DCDC converters datasheet the input range include 4.5V to 17V ?

I wish to keep 5V/2A power supply but I need to understand why 5V is out of range.

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Re: 5V or 12V

Post by crashoverride »

Cyrille wrote:
Thu Sep 23, 2021 6:45 pm
Why 12V DC IN whereas we regulate the output voltage to 5V, 3.3V and 1.8V
The main factor is power which is defined in watts. Watts = Voltage * Current
5V * 2A = 10W
12V * 2A = 24W = 5V * 4.8A

The amount of power required is more readily available from a 12V source.
Cyrille wrote:
Thu Sep 23, 2021 6:45 pm
Why specify an input voltage range from 5.5V to 13V whereas according to DCDC converters datasheet the input range include 4.5V to 17V
I counted five (5) voltage regulators attached to the DC jack (schematic sheet 30-31). While a power adapter may claim 5V output, its actually output may vary (higher/lower) and also may depend on load (ie. a 5V power adapter under full load may provide less than 4.5V). Additionally, there is voltage loss due to resistance of the wires connecting the adapter as well as PCB traces routing the power on the board. With five regulators, a 5.5V minimum specification is reasonable for reliable operation (across various environments).
Cyrille wrote:
Thu Sep 23, 2021 6:45 pm
I wish to keep 5V/2A power supply
You should measure the amount of power required by your use case. You should also measure the voltage of your 5V power supply. If your 5V adapter can provide the required power (volts * amps) under full load while maintaining 5V, it may work (use at your own risk).
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Re: 5V or 12V

Post by odroid »

The 5Volt step-down DCDC converter on the C4 board requires 300mV voltage drop in the edge conditions.
If your 5V/2A PSU can source very stable 5.3Volt at full load of 2Amp current without any hidden voltage drops such a DC cable or DC plug, you can use it.

But, we strongly recommend 12V/2A PSU as @crashoverride explained.
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Cyrille (Fri Sep 24, 2021 3:56 pm)

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Re: 5V or 12V

Post by Cyrille »

Yes, indeed. As the Buck Converter (JW5057C) provides a regulated 5V output we need to inject at least VIN = 5V + DropOut to step down to 5V so a 12V/2A is definitely required.
Nevertheless it doesn't have any link with power in my case as I explained above.

Thank you for your answers !

Cyrille

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Re: 5V or 12V

Post by wystewart »

would it be possible to modify the C4 to run from 5V. i don't need much power from the usb ports. thinking to remove L8 and jumper the dc jack to the internal 5v. but u25's enable is driven fron the gpio of the processor. If U25 is bypassed this enable function would not longer work, not sure what the side effects would be. does anyone know?

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Re: 5V or 12V

Post by mctom »

The thing is that higher current contributes to heat losses in cables and such. That is precisely the reason why we have high voltage in wall sockets and on power lines.
I imagine there are not many 5V 5A power supplies on the market, and 12V 2A is really easy to obtain.

As I stated a few times already around the Internet, I use Raspberry Pis with as low as 3.6V and they work just fine, except I don't expect USB to work at all.

@wystewart, if you don't care about USB or HDMI, just try if it works with direct 5V supply.
Or, if you feel like doing dirty tricks, you may replace U25 with USB power switch chip. Incidentally there are such switches in SOT23-5 and SOT23-6 packages that would make a killer mod for C4, but unfortunately, I skimmed through about 50 different models and none of them seems to have a suitable pinout to become a drop-in replacement.
So it could be done with a little bit of cable magic, but that's not so cool anymore. :(

Anyway the 5V_EN net is connected directly to SOC GPIO, 5V tolerant open drain type. No idea if it's ever used, given that the only thing it can do is to shutdown the power supply and brown out itself.

I'd probably just short pins 5 and 6 of U25 and see what happens, expect maybe some weird problems with shutdown or reset...

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