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NRF52840DK power issues. Delayed power on and inductor noise.

When I connected the usb and turn the DK switch on, the DK didn't turn on. After leaving for a few minutes, the DK started to turn on and off then eventually stables and fully on.

I can turn off or disconnect the usb and when connecting back again, it immediately turns on as it should.

But if I leave it unplug for hours, I'm having the power issues again. So I need to leave it for a few minutes sometimes hours until it turn on again before I can start my work.

Also, for the first few minutes the power stabilize, I can hear a noise that I think came from the inductor near usb or that area.

Please advise.

0 user97666 over 4 years ago

Hello Saiful Kah,

I have a similar issue. But my nRF5240DK turns ON after 10~15 seconds on connecting every time.

Regads,

Neeraj Dhekale
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0 user75734 over 4 years ago

Hi

This sounds very strange, please check with anothr USB cable, and if you are using a USB hub, try connecting it directly to a USB port on the computer instead. Can you also share some information about the DK? What revision of the nRF52840 DK is this, have you made any modifications to solder bridges or shorted any pins (maybe for current measurement purposes)? What position is the various switches in, and is the battery in the DK or not?

Best regards,

Simon
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0 user108531 over 4 years ago in reply to user75734

It is strange indeed. I tried with multiple high quality cables with same result. Not using any hub. Tried different ports on different laptops. NRF52840DK PCA10056 2.0.2 2021.25. No hardware modifications made. Never use it to measure current. Switch position: SW6=DEFAULT, SW9=VDD, SW7=Def, SW10=OFF, SW8=ON. Battery is in and working.
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0 user75734 over 4 years ago

Hi, thank you for confirming.

Can you try removing the battery and see if the problem persists? Also, this noise you describe sounds vaguely familiar but I don't recall the specifics, or if it was related to a power issue on the DK, so I have asked internally if anyone knows what could cause this. The initial response to the "won't turn on for minutes" is that you need to be more "determined" when you move the SW8 from OFF to ON. There have been some issues with customers being to "soft" on the switch.

Best regards,

Simon
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0 user75734 over 4 years ago

UPDATE: Another thing that might cause a delay in the power-up process is due to a weak pull-down on R88. Try to ground VIO_REF and see if that helps.

Best regards,

Simon
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