Damaged 3.3v regulator on Xiao BLE - what could be the cause?

Products & Technology XIAO
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#1

Today I experienced an unfortunate event where I the my Xiao nRF52840 seemed to die after trying to charge the battery (for the first time) via a USB-C power supply .

I was in a pinch, so I used the charger for my Dell laptop, I didn’t think much of it - I figured, while overkill, the Xiao wouldn’t draw any more current than it needs to. After I plugged it in, the LED went dark, and no matter what I tried, it wouldn’t come back on.
So I took out my multimeter and measured 5v present, but nothing on the 3.3v pin. Applying 3.3v directly to the 3.3v pin woke job the MCU again…

What could have caused this? did I inadvertently apply more voltage than i intended? I know the laptop charger is a PD charger but I assumed that it would default to 5v… could the 2500 mAh lipo battery have been too big and too much inrush current to try to charge it?

#2

Hi efm-7,

The absolute maximum input voltage of the 3.3V regulator SGM2040 is 8V.
Furthermore, the breakdown voltage of C4 and C9 is supposed to be 6.3V.

If your charger has an output voltage of 6.3 to 8V or higher, these are most likely damaged. On the other hand, the output current of the charge controller BQ25100 is set to 50 mA by default, so I don’t think the inrush current will destroy it.

I recommend that you check the circuit diagram to be sure.

#3

Hi there,
So typically the dell power supply’s are 19V Dc. you went WAY past the max = TOAST :bread:, also if you ever hook up the battery in reverse polarity and connect the USB you will kill the battery charger Chip and have a similar mode of operation after. as well as no battery charging any more.
The chips will still function but power levels will be flaky. YMMV :+1:

HTH
GL :slight_smile: PJ :v:

#4

So even though the Dell power power cord IS just a standard USB-C PD charger, it could have been fixed output at 20v? I thought with PD, there had to be a special sort of handshake to raise the voltage PAST the standard 5v….

#5

No only USB chargers afaik have that. Take a look at the USB_C wire spec,

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Could have been worse and , let the magic smoke out! :sweat_smile: :v:
GL :slight_smile: PJ
:+1:

#6

Hi,
The fact is that, if a power adapter can output 5V voltage, there will be related information marked on it, like this one from Apple. So please check the Dell power adapter you used.

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