On the raduino, the si5351 is sucking as much as 35ma+5.6ma=40.6ma of 3.3v from the Nano assembly
as per table 3 on p5 of ?https://www.silabs.com/documents/public/data-sheets/Si5351-B.pdf
That 3.3v comes from a regulator tucked inside the USB chip at U2, whatever the clones are stuffing there.
? ??
That's a very significant extra load on U2.
The USB chip at U2 is powered from the Nano's 5v rail which could come from 12v vin through the
dinky 5v regulator at U3, though on the Raduino we instead have a separate 5v LM7805 in a TO220. ?
The Raduino's TO220 can get quite hot.
The Raduino would likely blow U3 if it didn't have a separate TO220 LM7805,
even if U3 was an honest ua78m05 in the sot223
Unless shaving pennies, I'd tend to just feed the Nano 5v and not borrow any 3.3v from it.
Especially if getting pot-luck Nano clones from Ebay.
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On Sun, Oct 22, 2017 at 02:11 pm, David McGough wrote:
I'm designing a NANO project right now that uses the on-board regulator at about +12v input. I'm only powering the atmega328p chip and? 6 digital outputs, consisting of low-current LEDs/opto-isolators. I've had no problems, so far, with a random sampling of about a dozen cheapo boards....My max current draw is perhaps 25mA. How much current were you drawing from the regulator where it popped??
....Now I'm concerned that I may need to consider an external regulator.
