What is the best power source for rock 5b?

#1

I have a bench-top power supply with a range from 0-60V and output 5+ amps.
Should I connect it to the USB-C port or to the GPOIO pins?
And should I use 5V or something else?

#2

if you got a bench power supply and know the ranges you also know how it works with 5v

usb-c pd is a protocol to ramp up voltage wich your bench supply doesn’t have .

but a recent usb-c phone charger with at least 45w like from samsung or xiaomi works .

not all usb-c chargers work with voltage changes so it is safer to use a 5v supply with at least 3A.

#3
#4

What about the POE support?
At which pins the rock 5b expects to see voltage input from a POE hat?

Edit: I already have this https://www.raspberrypi.com/products/poe-plus-hat/. Is it compatible with rock 5b

#5

It looks like 5.05V from a bench power supply works very well.
I connected the plus lead from the supply to 2 and 4 GPIO pins and the minus lead to 6 and 9 GPIO pins.
A strange behavior is that when I poweroff the board with debian command it pulls ~20mA from the power supply when off. If I increase the voltage at 5.3V it pulls up to 400mA when off.
That is about 2W when off doing nothing.

Does anybody know why is this happening?

#6

is you board powered off ?

or is the cpu at deep sleep

#7

You can feed a fixed voltage up to 20 V in the USB-C port. See the Hardware wiki for details. It seems they suggest using at least 9 V. I use 12 V without any issues.

#8

When you supply power to the pins, you supply power to a part of the circuit that should be exactly 5 V. At 5.3 V, there might already be a protection circuit that tries to limit the voltage by drawing current. So something on your board will get hot that shouldn’t.

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#9

You should not exceed 5.0 V on the GPIO pins as you feed it directly in to the 5 V rail (maybe 5.1 V is ok). Its much safer to feed it via the USB-C port as it has a MP8759 DC/DC regulator with a wide input voltage range.

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#10

Samsung 45W Super Fast Charger Zero Issues so far

#11

Thanks
I will avoid voltages above 5.1V.
Do you how much below 5V can I go?

Regards.

#12

I already have the following from an other project:


which works OK for me.
I’m just looking for alternatives.
And I haven’t tested the rpi4 POE+ hat yet because is running my lightning node at the moment.

Edit:
An other option is the following:

signal-2023-02-28-130715
signal-2023-02-28-130715.jpeg1728×3072 558 KB

and this:
signal-2023-02-28-133519
signal-2023-02-28-133519.jpeg3072×1728 568 KB

#13

So, it suport as input 12V, or only 5V?

#14

When you insert voltage from the GPIO pins you want it to be as close possible to 5V and never exceed 5.1V because you are risking to damage the board.
When you use the USB-C port anything from 5-20V is acceptable. This goes thru a regulator which adjust it to be as close to 5V in order for the board to work normally.
When you use the GPIO pins you are responsible for the adjustment.

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#15

FYI,

my board, 5v feeded via USB-c from a 10A power supply, seems to work like a charm.
BUT if I start something that abrubtely puts load on the CPU (like stress-ng), the board reboots.

By feeding 12v (via USB-c), the problem disappear.

So if you face reboot issues with a 5v power supply, try another one with an higher voltage.