Xmega PLL multiplier [solved]

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I'm trying to run a chip at 4MHz (doesn't have to but I just want to for now).

It seems that the smallest mutiplier is 4 (8MHz), if I use 2 then the PLL is never ready and the code just hangs, any other value works ok.

So is it better running the PLL at a higher frequency and then use a divider?

Yeah, I know it's in the manual somehwere... :)

edit actually 3 also works (6MHz)

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

Last Edited: Fri. Dec 7, 2012 - 07:06 AM
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Using the X8 multiplier and dividing by 4 seems to work well, close enough for now.

Don't know why the X2 isn't working, it is supposed to work.

I'll mark the thread solved but if anyone wants to chip in, please feel free to do so. :-)

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

Last Edited: Fri. Dec 7, 2012 - 08:15 PM
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The datasheet says that the minimum PLL output frequency is 16MHz. I have had it run fine at 8MHz but 4MHz is probably pushing it too far.

Look at the power consumption of the PLL and 2MHz oscillators in the datasheet. You would actually be better off dividing down the 32MHz OSC instead.

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Quote:
minimum PLL output frequency is 16MHz
Saw something similar in one of the examples after I posted the above, it mentioned 10MHz minimum, I did look at the datasheet but it's a bit confusing the 1st time around. Too many choices!

The final board will have a crystal, the clock is working close enough now to continue my tests. I will look at the 32MHz clock and divide by 8.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly