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How is the power via USB filtered in an Arduino Nano

How is the power via USB filtered in an Arduino Nano

How is the power via USB filtered in an Arduino Nano

Hello all,

I have an issue with the 5V input to the Arduino Nano. I noticed that when I power (using a power bank) my Nano via the USB port I get a clean ADC reading from my microphone but using the same power via the Vin pin I am getting noise. This makes me think there is a filter in the path. I have attached the schematics, can someone identify what that filter is?


RE: How is the power via USB filtered in an Arduino Nano

If it is a genuine Arduino Nano there is a schematic and BOM at https://www.arduino.cc/en/uploads/Main/ArduinoNano...

It just looks like a couple of caps on the USB input, C8 and C9.

OTOH, there are a bunch of caps on the 5V rail, C2, C3, and C10.

RE: How is the power via USB filtered in an Arduino Nano

In that schematic, the USB adds C8 and C9 to C2, C3, and C10 via the Schottky diode D1, so ~50% more capacitance, but you do lose 0.1-0.2V through that diode.

But the noise could come from elsewhere, since a power bank is essentially pure DC. It may be that the FT232RL might be generating noise that's suppressed when it's connected to your power bank.

TTFN (ta ta for now)
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RE: How is the power via USB filtered in an Arduino Nano

That power bank could easily have a switcher in it.

Keith Cress
kcress - http://www.flaminsystems.com

RE: How is the power via USB filtered in an Arduino Nano

How about hooking it to a scope and seeing what this so-called noise looks like... that will probably give a gigantic clue as to where it is coming from.

Dan - Owner

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