I am working on a senior design project and am trying to embed an ATSAM3X8E (Here is the Application Sheet PDF) micro-controller into a system my team is designing. What is the pourpose of incorperating an inductor into the VDDUTMI (USB 3-3.6V input) and the VDDANA (for ADC and DAC supplies) ? I konw as a senior I should probably know this, but a little help is welcome.

Also, for the number 2 red circle, is that a symbol for a polarized capacitor? I am not used to this representation.

EDIT: Also, why is there no value for the resistor?? What does 1R mean?

(This above schematic can be found on page 4 of the application note file.)

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1 - The two 10 uH inductors are RF chokes which keep external noise picked up on the UTMI+ interface (such as USB cables) from getting back into the ADC and causing noise.

2 - Yes, those are all electrolytics, presumably tantalums.

3 - The symbols are indeed resistors, 1R stands for 1 ohm. A common convention for resistors is to use XRXX to indicate X.XX ohms, XkXX for X.XX kohms, XMXX for X.XX Mohms, etc.


The inductor is probably used to improve noise filtering on the supply lines

Since the two electrodes of the capacitor are shown differently, this implies to me that it is a polarized capacitor (electrolytic), although I don't think I've seen that particular symbol before.

For some reason the resistor symbols don't appear in my browser. However, I expect that "1R" means the resistor value is 1 Ohm.


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