Powering using SYS_5V


I am trying to power my BBB from an external 12V source.

I convert it to 5V using D15V35F5S3 step down convertor from Pololu.

When I connect it to SYS_5V it works but I have to always hit the power button before the lights go on.

Do you know any way to not to have to hit the POWER button ?

Thank you very much.

You could add a toggle switch between the power supply and the BBB, or more simply just not power the BBB down. Leave it up.


Thanks for your reponse.

I meant that after the power is beeing supplied to the BBB. I have to hit the POWER button in order to make it start.

I did not have to do this when it was powered from sector.

You need to put an oscilloscope on the 5 Volt output from the Pololu.
There is a rise time specification on the start-up Voltage rise time.
I think it needs to reach 5.0 Volts in less than 50 milliseconds.
Read the System Reference Manual

The Voltage can not overshoot more than a few tenths of a Volt.
The operating Voltage should be 5.0 Volts plus or minus 0.25 Volts.

If it overshoots or undershoots above 5.5 or below 4.5 for even a millisecond,
the PMIC will shut down.

A properly designed 12 Volt to 5 Volt converter will work fine, every time.

— Graham