Problem with 5V


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?

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

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?

tiistai 7. marraskuuta 2017 21.56.24 UTC+2 Graham kirjoitti:

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