Problem with 5V

[pahv...@gmail.com]

Hello.

With 5V power, BBB not starting normally, only power led flashes 1 time. And if i connect USB without 5V PSU it starting up. 

Is there something broken or what? 

[Graham]

The one time flash means that the Power Management Integrated Circuit (PMIC) saw something about your power that it did not like and went into self-protect.

The 5 V power for the BBB must remain between 4.5 and 5.5 Volts at all times. even a transition out of that range for a millisecond or so will trip the self protect.

There are also some rise-time requiremetns when the power is turned on.

It is best to stay between 4.75 and 5.25, so that you have some margin, against the self-protect points.

Put an oscilloscope on your 5V power and figure out what is happening.

--- Graham

==

[pekkaj...@gmail.com]

thanks for the answer. i think i need to find other power and test with that. If that new one stays 4.75 - 5.25 it will working normally then?
how about that, im thinking to run it with USB power via USB connector. is it ok?

[Graham Haddock]

Yes, try some other power supplies. and if they stay between 4.75 and 5.25 under all the different load conditions a BBB can create, it will work fine.

USB power is highly variable from computer to computer.  Sometimes it works fine, sometimes it does not.

USB-1 was 0.5 Amps max, not enough to run a BBB, while booting or updating the eMMC.

USB-2 is 0.9 Amps, about enough to handle the peak current from a BBB.

The Voltage limits for USB are 4.5 to 5.5 Volts. No margin if at the limits under full load.

--- Graham

==